xref: /petsc/src/mat/impls/aij/mpi/mpiov.c (revision 93f4724e78738d7143aa68df3190530a8573830a)
1 /*
2    Routines to compute overlapping regions of a parallel MPI matrix
3   and to find submatrices that were shared across processors.
4 */
5 #include <../src/mat/impls/aij/seq/aij.h>
6 #include <../src/mat/impls/aij/mpi/mpiaij.h>
7 #include <petscbt.h>
8 #include <petscsf.h>
9 
10 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Once(Mat,PetscInt,IS*);
11 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Local(Mat,PetscInt,char**,PetscInt*,PetscInt**,PetscTable*);
12 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Receive(Mat,PetscInt,PetscInt**,PetscInt**,PetscInt*);
13 extern PetscErrorCode MatGetRow_MPIAIJ(Mat,PetscInt,PetscInt*,PetscInt**,PetscScalar**);
14 extern PetscErrorCode MatRestoreRow_MPIAIJ(Mat,PetscInt,PetscInt*,PetscInt**,PetscScalar**);
15 
16 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Once_Scalable(Mat,PetscInt,IS*);
17 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Local_Scalable(Mat,PetscInt,IS*);
18 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Send_Scalable(Mat,PetscInt,PetscMPIInt,PetscMPIInt *,PetscInt *, PetscInt *,PetscInt **,PetscInt **);
19 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Receive_Scalable(Mat,PetscInt,IS*,PetscInt,PetscInt *);
20 
21 
22 PetscErrorCode MatIncreaseOverlap_MPIAIJ(Mat C,PetscInt imax,IS is[],PetscInt ov)
23 {
24   PetscErrorCode ierr;
25   PetscInt       i;
26 
27   PetscFunctionBegin;
28   if (ov < 0) SETERRQ(PetscObjectComm((PetscObject)C),PETSC_ERR_ARG_OUTOFRANGE,"Negative overlap specified");
29   for (i=0; i<ov; ++i) {
30     ierr = MatIncreaseOverlap_MPIAIJ_Once(C,imax,is);CHKERRQ(ierr);
31   }
32   PetscFunctionReturn(0);
33 }
34 
35 PetscErrorCode MatIncreaseOverlap_MPIAIJ_Scalable(Mat C,PetscInt imax,IS is[],PetscInt ov)
36 {
37   PetscErrorCode ierr;
38   PetscInt       i;
39 
40   PetscFunctionBegin;
41   if (ov < 0) SETERRQ(PetscObjectComm((PetscObject)C),PETSC_ERR_ARG_OUTOFRANGE,"Negative overlap specified");
42   for (i=0; i<ov; ++i) {
43     ierr = MatIncreaseOverlap_MPIAIJ_Once_Scalable(C,imax,is);CHKERRQ(ierr);
44   }
45   PetscFunctionReturn(0);
46 }
47 
48 
49 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Once_Scalable(Mat mat,PetscInt nidx,IS is[])
50 {
51   PetscErrorCode   ierr;
52   MPI_Comm         comm;
53   PetscInt        *length,length_i,tlength,*remoterows,nrrows,reducednrrows,*rrow_ranks,*rrow_isids,i,j,owner;
54   PetscInt         *tosizes,*tosizes_temp,*toffsets,*fromsizes,*todata,*fromdata;
55   PetscInt         nrecvrows,*sbsizes = 0,*sbdata = 0;
56   const PetscInt  *indices_i,**indices;
57   PetscLayout      rmap;
58   PetscMPIInt      rank,size,*toranks,*fromranks,nto,nfrom;
59   PetscSF          sf;
60   PetscSFNode     *remote;
61 
62   PetscFunctionBegin;
63   ierr = PetscObjectGetComm((PetscObject)mat,&comm);CHKERRQ(ierr);
64   ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
65   ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr);
66   /* get row map to determine where rows should be going */
67   ierr = MatGetLayouts(mat,&rmap,NULL);CHKERRQ(ierr);
68   /* retrieve IS data and put all together so that we
69    * can optimize communication
70    *  */
71   ierr = PetscCalloc2(nidx,(PetscInt ***)&indices,nidx,&length);CHKERRQ(ierr);
72   for (i=0,tlength=0; i<nidx; i++){
73     ierr = ISGetLocalSize(is[i],&length[i]);CHKERRQ(ierr);
74     tlength += length[i];
75     ierr = ISGetIndices(is[i],&indices[i]);CHKERRQ(ierr);
76   }
77   /* find these rows on remote processors */
78   ierr = PetscCalloc3(tlength,&remoterows,tlength,&rrow_ranks,tlength,&rrow_isids);CHKERRQ(ierr);
79   ierr = PetscCalloc3(size,&toranks,2*size,&tosizes,size,&tosizes_temp);CHKERRQ(ierr);
80   nrrows = 0;
81   for (i=0; i<nidx; i++){
82     length_i     = length[i];
83     indices_i    = indices[i];
84     for (j=0; j<length_i; j++){
85       owner = -1;
86       ierr = PetscLayoutFindOwner(rmap,indices_i[j],&owner);CHKERRQ(ierr);
87       /* remote processors */
88       if (owner != rank){
89         tosizes_temp[owner]++; /* number of rows to owner */
90         rrow_ranks[nrrows]  = owner; /* processor */
91         rrow_isids[nrrows]   = i; /* is id */
92         remoterows[nrrows++] = indices_i[j]; /* row */
93       }
94     }
95     ierr = ISRestoreIndices(is[i],&indices[i]);CHKERRQ(ierr);
96   }
97   ierr = PetscFree2(indices,length);CHKERRQ(ierr);
98   /* test if we need to exchange messages
99    * generally speaking, we do not need to exchange
100    * data when overlap is 1
101    * */
102   ierr = MPIU_Allreduce(&nrrows,&reducednrrows,1,MPIU_INT,MPIU_MAX,comm);CHKERRQ(ierr);
103   /* we do not have any messages
104    * It usually corresponds to overlap 1
105    * */
106   if (!reducednrrows){
107     ierr = PetscFree3(toranks,tosizes,tosizes_temp);CHKERRQ(ierr);
108     ierr = PetscFree3(remoterows,rrow_ranks,rrow_isids);CHKERRQ(ierr);
109     ierr = MatIncreaseOverlap_MPIAIJ_Local_Scalable(mat,nidx,is);CHKERRQ(ierr);
110     PetscFunctionReturn(0);
111   }
112   nto = 0;
113   /* send sizes and ranks for building a two-sided communcation */
114   for (i=0; i<size; i++){
115    if (tosizes_temp[i]){
116      tosizes[nto*2]  = tosizes_temp[i]*2; /* size */
117      tosizes_temp[i] = nto; /* a map from processor to index */
118      toranks[nto++]  = i; /* processor */
119    }
120   }
121   ierr = PetscCalloc1(nto+1,&toffsets);CHKERRQ(ierr);
122   for (i=0; i<nto; i++){
123     toffsets[i+1]  = toffsets[i]+tosizes[2*i]; /* offsets */
124     tosizes[2*i+1] = toffsets[i]; /* offsets to send */
125   }
126   /* send information to other processors */
127   ierr = PetscCommBuildTwoSided(comm,2,MPIU_INT,nto,toranks,tosizes,&nfrom,&fromranks,&fromsizes);CHKERRQ(ierr);
128   nrecvrows = 0;
129   for (i=0; i<nfrom; i++) nrecvrows += fromsizes[2*i];
130   ierr = PetscMalloc1(nrecvrows,&remote);CHKERRQ(ierr);
131   nrecvrows = 0;
132   for (i=0; i<nfrom; i++){
133     for (j=0; j<fromsizes[2*i]; j++){
134       remote[nrecvrows].rank    = fromranks[i];
135       remote[nrecvrows++].index = fromsizes[2*i+1]+j;
136     }
137   }
138   ierr = PetscSFCreate(comm,&sf);CHKERRQ(ierr);
139   ierr = PetscSFSetGraph(sf,nrecvrows,nrecvrows,NULL,PETSC_OWN_POINTER,remote,PETSC_OWN_POINTER);CHKERRQ(ierr);
140   /* use two-sided communication by default since OPENMPI has some bugs for one-sided one */
141   ierr = PetscSFSetType(sf,PETSCSFBASIC);CHKERRQ(ierr);
142   ierr = PetscSFSetFromOptions(sf);CHKERRQ(ierr);
143   /* message pair <no of is, row>  */
144   ierr = PetscCalloc2(2*nrrows,&todata,nrecvrows,&fromdata);CHKERRQ(ierr);
145   for (i=0; i<nrrows; i++){
146     owner = rrow_ranks[i]; /* processor */
147     j     = tosizes_temp[owner]; /* index */
148     todata[toffsets[j]++] = rrow_isids[i];
149     todata[toffsets[j]++] = remoterows[i];
150   }
151   ierr = PetscFree3(toranks,tosizes,tosizes_temp);CHKERRQ(ierr);
152   ierr = PetscFree3(remoterows,rrow_ranks,rrow_isids);CHKERRQ(ierr);
153   ierr = PetscFree(toffsets);CHKERRQ(ierr);
154   ierr = PetscSFBcastBegin(sf,MPIU_INT,todata,fromdata);CHKERRQ(ierr);
155   ierr = PetscSFBcastEnd(sf,MPIU_INT,todata,fromdata);CHKERRQ(ierr);
156   ierr = PetscSFDestroy(&sf);CHKERRQ(ierr);
157   /* send rows belonging to the remote so that then we could get the overlapping data back */
158   ierr = MatIncreaseOverlap_MPIAIJ_Send_Scalable(mat,nidx,nfrom,fromranks,fromsizes,fromdata,&sbsizes,&sbdata);CHKERRQ(ierr);
159   ierr = PetscFree2(todata,fromdata);CHKERRQ(ierr);
160   ierr = PetscFree(fromsizes);CHKERRQ(ierr);
161   ierr = PetscCommBuildTwoSided(comm,2,MPIU_INT,nfrom,fromranks,sbsizes,&nto,&toranks,&tosizes);CHKERRQ(ierr);
162   ierr = PetscFree(fromranks);CHKERRQ(ierr);
163   nrecvrows = 0;
164   for (i=0; i<nto; i++) nrecvrows += tosizes[2*i];
165   ierr = PetscCalloc1(nrecvrows,&todata);CHKERRQ(ierr);
166   ierr = PetscMalloc1(nrecvrows,&remote);CHKERRQ(ierr);
167   nrecvrows = 0;
168   for (i=0; i<nto; i++){
169     for (j=0; j<tosizes[2*i]; j++){
170       remote[nrecvrows].rank    = toranks[i];
171       remote[nrecvrows++].index = tosizes[2*i+1]+j;
172     }
173   }
174   ierr = PetscSFCreate(comm,&sf);CHKERRQ(ierr);
175   ierr = PetscSFSetGraph(sf,nrecvrows,nrecvrows,NULL,PETSC_OWN_POINTER,remote,PETSC_OWN_POINTER);CHKERRQ(ierr);
176   /* use two-sided communication by default since OPENMPI has some bugs for one-sided one */
177   ierr = PetscSFSetType(sf,PETSCSFBASIC);CHKERRQ(ierr);
178   ierr = PetscSFSetFromOptions(sf);CHKERRQ(ierr);
179   /* overlap communication and computation */
180   ierr = PetscSFBcastBegin(sf,MPIU_INT,sbdata,todata);CHKERRQ(ierr);
181   ierr = MatIncreaseOverlap_MPIAIJ_Local_Scalable(mat,nidx,is);CHKERRQ(ierr);
182   ierr = PetscSFBcastEnd(sf,MPIU_INT,sbdata,todata);CHKERRQ(ierr);
183   ierr = PetscSFDestroy(&sf);CHKERRQ(ierr);
184   ierr = PetscFree2(sbdata,sbsizes);CHKERRQ(ierr);
185   ierr = MatIncreaseOverlap_MPIAIJ_Receive_Scalable(mat,nidx,is,nrecvrows,todata);CHKERRQ(ierr);
186   ierr = PetscFree(toranks);CHKERRQ(ierr);
187   ierr = PetscFree(tosizes);CHKERRQ(ierr);
188   ierr = PetscFree(todata);CHKERRQ(ierr);
189   PetscFunctionReturn(0);
190 }
191 
192 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Receive_Scalable(Mat mat,PetscInt nidx, IS is[], PetscInt nrecvs, PetscInt *recvdata)
193 {
194   PetscInt         *isz,isz_i,i,j,is_id, data_size;
195   PetscInt          col,lsize,max_lsize,*indices_temp, *indices_i;
196   const PetscInt   *indices_i_temp;
197   PetscErrorCode    ierr;
198 
199   PetscFunctionBegin;
200   max_lsize = 0;
201   ierr = PetscMalloc1(nidx,&isz);CHKERRQ(ierr);
202   for (i=0; i<nidx; i++){
203     ierr = ISGetLocalSize(is[i],&lsize);CHKERRQ(ierr);
204     max_lsize = lsize>max_lsize ? lsize:max_lsize;
205     isz[i]    = lsize;
206   }
207   ierr = PetscMalloc1((max_lsize+nrecvs)*nidx,&indices_temp);CHKERRQ(ierr);
208   for (i=0; i<nidx; i++){
209     ierr = ISGetIndices(is[i],&indices_i_temp);CHKERRQ(ierr);
210     ierr = PetscMemcpy(indices_temp+i*(max_lsize+nrecvs),indices_i_temp, sizeof(PetscInt)*isz[i]);CHKERRQ(ierr);
211     ierr = ISRestoreIndices(is[i],&indices_i_temp);CHKERRQ(ierr);
212     ierr = ISDestroy(&is[i]);CHKERRQ(ierr);
213   }
214   /* retrieve information to get row id and its overlap */
215   for (i=0; i<nrecvs; ){
216     is_id      = recvdata[i++];
217     data_size  = recvdata[i++];
218     indices_i  = indices_temp+(max_lsize+nrecvs)*is_id;
219     isz_i      = isz[is_id];
220     for (j=0; j< data_size; j++){
221       col = recvdata[i++];
222       indices_i[isz_i++] = col;
223     }
224     isz[is_id] = isz_i;
225   }
226   /* remove duplicate entities */
227   for (i=0; i<nidx; i++){
228     indices_i  = indices_temp+(max_lsize+nrecvs)*i;
229     isz_i      = isz[i];
230     ierr = PetscSortRemoveDupsInt(&isz_i,indices_i);CHKERRQ(ierr);
231     ierr = ISCreateGeneral(PETSC_COMM_SELF,isz_i,indices_i,PETSC_COPY_VALUES,&is[i]);CHKERRQ(ierr);
232   }
233   ierr = PetscFree(isz);CHKERRQ(ierr);
234   ierr = PetscFree(indices_temp);CHKERRQ(ierr);
235   PetscFunctionReturn(0);
236 }
237 
238 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Send_Scalable(Mat mat,PetscInt nidx, PetscMPIInt nfrom,PetscMPIInt *fromranks,PetscInt *fromsizes, PetscInt *fromrows, PetscInt **sbrowsizes, PetscInt **sbrows)
239 {
240   PetscLayout       rmap,cmap;
241   PetscInt          i,j,k,l,*rows_i,*rows_data_ptr,**rows_data,max_fszs,rows_pos,*rows_pos_i;
242   PetscInt          is_id,tnz,an,bn,rstart,cstart,row,start,end,col,totalrows,*sbdata;
243   PetscInt         *indv_counts,indvc_ij,*sbsizes,*indices_tmp,*offsets;
244   const PetscInt   *gcols,*ai,*aj,*bi,*bj;
245   Mat               amat,bmat;
246   PetscMPIInt       rank;
247   PetscBool         done;
248   MPI_Comm          comm;
249   PetscErrorCode    ierr;
250 
251   PetscFunctionBegin;
252   ierr = PetscObjectGetComm((PetscObject)mat,&comm);CHKERRQ(ierr);
253   ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
254   ierr = MatMPIAIJGetSeqAIJ(mat,&amat,&bmat,&gcols);CHKERRQ(ierr);
255   /* Even if the mat is symmetric, we still assume it is not symmetric */
256   ierr = MatGetRowIJ(amat,0,PETSC_FALSE,PETSC_FALSE,&an,&ai,&aj,&done);CHKERRQ(ierr);
257   if (!done) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"can not get row IJ \n");
258   ierr = MatGetRowIJ(bmat,0,PETSC_FALSE,PETSC_FALSE,&bn,&bi,&bj,&done);CHKERRQ(ierr);
259   if (!done) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"can not get row IJ \n");
260   /* total number of nonzero values is used to estimate the memory usage in the next step */
261   tnz  = ai[an]+bi[bn];
262   ierr = MatGetLayouts(mat,&rmap,&cmap);CHKERRQ(ierr);
263   ierr = PetscLayoutGetRange(rmap,&rstart,NULL);CHKERRQ(ierr);
264   ierr = PetscLayoutGetRange(cmap,&cstart,NULL);CHKERRQ(ierr);
265   /* to find the longest message */
266   max_fszs = 0;
267   for (i=0; i<nfrom; i++) max_fszs = fromsizes[2*i]>max_fszs ? fromsizes[2*i]:max_fszs;
268   /* better way to estimate number of nonzero in the mat??? */
269   ierr = PetscCalloc5(max_fszs*nidx,&rows_data_ptr,nidx,&rows_data,nidx,&rows_pos_i,nfrom*nidx,&indv_counts,tnz,&indices_tmp);CHKERRQ(ierr);
270   for (i=0; i<nidx; i++) rows_data[i] = rows_data_ptr+max_fszs*i;
271   rows_pos  = 0;
272   totalrows = 0;
273   for (i=0; i<nfrom; i++){
274     ierr = PetscMemzero(rows_pos_i,sizeof(PetscInt)*nidx);CHKERRQ(ierr);
275     /* group data together */
276     for (j=0; j<fromsizes[2*i]; j+=2){
277       is_id                       = fromrows[rows_pos++];/* no of is */
278       rows_i                      = rows_data[is_id];
279       rows_i[rows_pos_i[is_id]++] = fromrows[rows_pos++];/* row */
280     }
281     /* estimate a space to avoid multiple allocations  */
282     for (j=0; j<nidx; j++){
283       indvc_ij = 0;
284       rows_i   = rows_data[j];
285       for (l=0; l<rows_pos_i[j]; l++){
286         row    = rows_i[l]-rstart;
287         start  = ai[row];
288         end    = ai[row+1];
289         for (k=start; k<end; k++){ /* Amat */
290           col = aj[k] + cstart;
291           indices_tmp[indvc_ij++] = col;/* do not count the rows from the original rank */
292         }
293         start = bi[row];
294         end   = bi[row+1];
295         for (k=start; k<end; k++) { /* Bmat */
296           col = gcols[bj[k]];
297           indices_tmp[indvc_ij++] = col;
298         }
299       }
300       ierr = PetscSortRemoveDupsInt(&indvc_ij,indices_tmp);CHKERRQ(ierr);
301       indv_counts[i*nidx+j] = indvc_ij;
302       totalrows            += indvc_ij;
303     }
304   }
305   /* message triple <no of is, number of rows, rows> */
306   ierr = PetscCalloc2(totalrows+nidx*nfrom*2,&sbdata,2*nfrom,&sbsizes);CHKERRQ(ierr);
307   totalrows = 0;
308   rows_pos  = 0;
309   /* use this code again */
310   for (i=0;i<nfrom;i++){
311     ierr = PetscMemzero(rows_pos_i,sizeof(PetscInt)*nidx);CHKERRQ(ierr);
312     for (j=0; j<fromsizes[2*i]; j+=2){
313       is_id                       = fromrows[rows_pos++];
314       rows_i                      = rows_data[is_id];
315       rows_i[rows_pos_i[is_id]++] = fromrows[rows_pos++];
316     }
317     /* add data  */
318     for (j=0; j<nidx; j++){
319       if (!indv_counts[i*nidx+j]) continue;
320       indvc_ij = 0;
321       sbdata[totalrows++] = j;
322       sbdata[totalrows++] = indv_counts[i*nidx+j];
323       sbsizes[2*i]       += 2;
324       rows_i              = rows_data[j];
325       for (l=0; l<rows_pos_i[j]; l++){
326         row   = rows_i[l]-rstart;
327         start = ai[row];
328         end   = ai[row+1];
329         for (k=start; k<end; k++){ /* Amat */
330           col = aj[k] + cstart;
331           indices_tmp[indvc_ij++] = col;
332         }
333         start = bi[row];
334         end   = bi[row+1];
335         for (k=start; k<end; k++) { /* Bmat */
336           col = gcols[bj[k]];
337           indices_tmp[indvc_ij++] = col;
338         }
339       }
340       ierr = PetscSortRemoveDupsInt(&indvc_ij,indices_tmp);CHKERRQ(ierr);
341       sbsizes[2*i]  += indvc_ij;
342       ierr = PetscMemcpy(sbdata+totalrows,indices_tmp,sizeof(PetscInt)*indvc_ij);CHKERRQ(ierr);
343       totalrows += indvc_ij;
344     }
345   }
346   ierr = PetscCalloc1(nfrom+1,&offsets);CHKERRQ(ierr);
347   for (i=0; i<nfrom; i++){
348     offsets[i+1]   = offsets[i] + sbsizes[2*i];
349     sbsizes[2*i+1] = offsets[i];
350   }
351   ierr = PetscFree(offsets);CHKERRQ(ierr);
352   if (sbrowsizes) *sbrowsizes = sbsizes;
353   if (sbrows) *sbrows = sbdata;
354   ierr = PetscFree5(rows_data_ptr,rows_data,rows_pos_i,indv_counts,indices_tmp);CHKERRQ(ierr);
355   ierr = MatRestoreRowIJ(amat,0,PETSC_FALSE,PETSC_FALSE,&an,&ai,&aj,&done);CHKERRQ(ierr);
356   ierr = MatRestoreRowIJ(bmat,0,PETSC_FALSE,PETSC_FALSE,&bn,&bi,&bj,&done);CHKERRQ(ierr);
357   PetscFunctionReturn(0);
358 }
359 
360 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Local_Scalable(Mat mat,PetscInt nidx, IS is[])
361 {
362   const PetscInt   *gcols,*ai,*aj,*bi,*bj, *indices;
363   PetscInt          tnz,an,bn,i,j,row,start,end,rstart,cstart,col,k,*indices_temp;
364   PetscInt          lsize,lsize_tmp,owner;
365   PetscMPIInt       rank;
366   Mat               amat,bmat;
367   PetscBool         done;
368   PetscLayout       cmap,rmap;
369   MPI_Comm          comm;
370   PetscErrorCode    ierr;
371 
372   PetscFunctionBegin;
373   ierr = PetscObjectGetComm((PetscObject)mat,&comm);CHKERRQ(ierr);
374   ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
375   ierr = MatMPIAIJGetSeqAIJ(mat,&amat,&bmat,&gcols);CHKERRQ(ierr);
376   ierr = MatGetRowIJ(amat,0,PETSC_FALSE,PETSC_FALSE,&an,&ai,&aj,&done);CHKERRQ(ierr);
377   if (!done) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"can not get row IJ \n");
378   ierr = MatGetRowIJ(bmat,0,PETSC_FALSE,PETSC_FALSE,&bn,&bi,&bj,&done);CHKERRQ(ierr);
379   if (!done) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"can not get row IJ \n");
380   /* is it a safe way to compute number of nonzero values ? */
381   tnz  = ai[an]+bi[bn];
382   ierr = MatGetLayouts(mat,&rmap,&cmap);CHKERRQ(ierr);
383   ierr = PetscLayoutGetRange(rmap,&rstart,NULL);CHKERRQ(ierr);
384   ierr = PetscLayoutGetRange(cmap,&cstart,NULL);CHKERRQ(ierr);
385   /* it is a better way to estimate memory than the old implementation
386    * where global size of matrix is used
387    * */
388   ierr = PetscMalloc1(tnz,&indices_temp);CHKERRQ(ierr);
389   for (i=0; i<nidx; i++) {
390     ierr = ISGetLocalSize(is[i],&lsize);CHKERRQ(ierr);
391     ierr = ISGetIndices(is[i],&indices);CHKERRQ(ierr);
392     lsize_tmp = 0;
393     for (j=0; j<lsize; j++) {
394       owner = -1;
395       row   = indices[j];
396       ierr = PetscLayoutFindOwner(rmap,row,&owner);CHKERRQ(ierr);
397       if (owner != rank) continue;
398       /* local number */
399       row  -= rstart;
400       start = ai[row];
401       end   = ai[row+1];
402       for (k=start; k<end; k++) { /* Amat */
403         col = aj[k] + cstart;
404         indices_temp[lsize_tmp++] = col;
405       }
406       start = bi[row];
407       end   = bi[row+1];
408       for (k=start; k<end; k++) { /* Bmat */
409         col = gcols[bj[k]];
410         indices_temp[lsize_tmp++] = col;
411       }
412     }
413    ierr = ISRestoreIndices(is[i],&indices);CHKERRQ(ierr);
414    ierr = ISDestroy(&is[i]);CHKERRQ(ierr);
415    ierr = PetscSortRemoveDupsInt(&lsize_tmp,indices_temp);CHKERRQ(ierr);
416    ierr = ISCreateGeneral(PETSC_COMM_SELF,lsize_tmp,indices_temp,PETSC_COPY_VALUES,&is[i]);CHKERRQ(ierr);
417   }
418   ierr = PetscFree(indices_temp);CHKERRQ(ierr);
419   ierr = MatRestoreRowIJ(amat,0,PETSC_FALSE,PETSC_FALSE,&an,&ai,&aj,&done);CHKERRQ(ierr);
420   ierr = MatRestoreRowIJ(bmat,0,PETSC_FALSE,PETSC_FALSE,&bn,&bi,&bj,&done);CHKERRQ(ierr);
421   PetscFunctionReturn(0);
422 }
423 
424 
425 /*
426   Sample message format:
427   If a processor A wants processor B to process some elements corresponding
428   to index sets is[1],is[5]
429   mesg [0] = 2   (no of index sets in the mesg)
430   -----------
431   mesg [1] = 1 => is[1]
432   mesg [2] = sizeof(is[1]);
433   -----------
434   mesg [3] = 5  => is[5]
435   mesg [4] = sizeof(is[5]);
436   -----------
437   mesg [5]
438   mesg [n]  datas[1]
439   -----------
440   mesg[n+1]
441   mesg[m]  data(is[5])
442   -----------
443 
444   Notes:
445   nrqs - no of requests sent (or to be sent out)
446   nrqr - no of requests recieved (which have to be or which have been processed
447 */
448 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Once(Mat C,PetscInt imax,IS is[])
449 {
450   Mat_MPIAIJ     *c = (Mat_MPIAIJ*)C->data;
451   PetscMPIInt    *w1,*w2,nrqr,*w3,*w4,*onodes1,*olengths1,*onodes2,*olengths2;
452   const PetscInt **idx,*idx_i;
453   PetscInt       *n,**data,len;
454 #if defined(PETSC_USE_CTABLE)
455   PetscTable     *table_data,table_data_i;
456   PetscInt       *tdata,tcount,tcount_max;
457 #else
458   PetscInt       *data_i,*d_p;
459 #endif
460   PetscErrorCode ierr;
461   PetscMPIInt    size,rank,tag1,tag2;
462   PetscInt       M,i,j,k,**rbuf,row,proc = 0,nrqs,msz,**outdat,**ptr;
463   PetscInt       *ctr,*pa,*tmp,*isz,*isz1,**xdata,**rbuf2;
464   PetscBT        *table;
465   MPI_Comm       comm;
466   MPI_Request    *s_waits1,*r_waits1,*s_waits2,*r_waits2;
467   MPI_Status     *s_status,*recv_status;
468   char           *t_p;
469 
470   PetscFunctionBegin;
471   ierr = PetscObjectGetComm((PetscObject)C,&comm);CHKERRQ(ierr);
472   size = c->size;
473   rank = c->rank;
474   M    = C->rmap->N;
475 
476   ierr = PetscObjectGetNewTag((PetscObject)C,&tag1);CHKERRQ(ierr);
477   ierr = PetscObjectGetNewTag((PetscObject)C,&tag2);CHKERRQ(ierr);
478 
479   ierr = PetscMalloc2(imax,&idx,imax,&n);CHKERRQ(ierr);
480 
481   for (i=0; i<imax; i++) {
482     ierr = ISGetIndices(is[i],&idx[i]);CHKERRQ(ierr);
483     ierr = ISGetLocalSize(is[i],&n[i]);CHKERRQ(ierr);
484   }
485 
486   /* evaluate communication - mesg to who,length of mesg, and buffer space
487      required. Based on this, buffers are allocated, and data copied into them  */
488   ierr = PetscMalloc4(size,&w1,size,&w2,size,&w3,size,&w4);CHKERRQ(ierr);
489   ierr = PetscMemzero(w1,size*sizeof(PetscMPIInt));CHKERRQ(ierr); /* initialise work vector*/
490   ierr = PetscMemzero(w2,size*sizeof(PetscMPIInt));CHKERRQ(ierr); /* initialise work vector*/
491   ierr = PetscMemzero(w3,size*sizeof(PetscMPIInt));CHKERRQ(ierr); /* initialise work vector*/
492   for (i=0; i<imax; i++) {
493     ierr  = PetscMemzero(w4,size*sizeof(PetscMPIInt));CHKERRQ(ierr); /* initialise work vector*/
494     idx_i = idx[i];
495     len   = n[i];
496     for (j=0; j<len; j++) {
497       row = idx_i[j];
498       if (row < 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Index set cannot have negative entries");
499       ierr = PetscLayoutFindOwner(C->rmap,row,&proc);CHKERRQ(ierr);
500       w4[proc]++;
501     }
502     for (j=0; j<size; j++) {
503       if (w4[j]) { w1[j] += w4[j]; w3[j]++;}
504     }
505   }
506 
507   nrqs     = 0;              /* no of outgoing messages */
508   msz      = 0;              /* total mesg length (for all proc */
509   w1[rank] = 0;              /* no mesg sent to intself */
510   w3[rank] = 0;
511   for (i=0; i<size; i++) {
512     if (w1[i])  {w2[i] = 1; nrqs++;} /* there exists a message to proc i */
513   }
514   /* pa - is list of processors to communicate with */
515   ierr = PetscMalloc1(nrqs+1,&pa);CHKERRQ(ierr);
516   for (i=0,j=0; i<size; i++) {
517     if (w1[i]) {pa[j] = i; j++;}
518   }
519 
520   /* Each message would have a header = 1 + 2*(no of IS) + data */
521   for (i=0; i<nrqs; i++) {
522     j      = pa[i];
523     w1[j] += w2[j] + 2*w3[j];
524     msz   += w1[j];
525   }
526 
527   /* Determine the number of messages to expect, their lengths, from from-ids */
528   ierr = PetscGatherNumberOfMessages(comm,w2,w1,&nrqr);CHKERRQ(ierr);
529   ierr = PetscGatherMessageLengths(comm,nrqs,nrqr,w1,&onodes1,&olengths1);CHKERRQ(ierr);
530 
531   /* Now post the Irecvs corresponding to these messages */
532   ierr = PetscPostIrecvInt(comm,tag1,nrqr,onodes1,olengths1,&rbuf,&r_waits1);CHKERRQ(ierr);
533 
534   /* Allocate Memory for outgoing messages */
535   ierr = PetscMalloc4(size,&outdat,size,&ptr,msz,&tmp,size,&ctr);CHKERRQ(ierr);
536   ierr = PetscMemzero(outdat,size*sizeof(PetscInt*));CHKERRQ(ierr);
537   ierr = PetscMemzero(ptr,size*sizeof(PetscInt*));CHKERRQ(ierr);
538 
539   {
540     PetscInt *iptr = tmp,ict  = 0;
541     for (i=0; i<nrqs; i++) {
542       j         = pa[i];
543       iptr     +=  ict;
544       outdat[j] = iptr;
545       ict       = w1[j];
546     }
547   }
548 
549   /* Form the outgoing messages */
550   /* plug in the headers */
551   for (i=0; i<nrqs; i++) {
552     j            = pa[i];
553     outdat[j][0] = 0;
554     ierr         = PetscMemzero(outdat[j]+1,2*w3[j]*sizeof(PetscInt));CHKERRQ(ierr);
555     ptr[j]       = outdat[j] + 2*w3[j] + 1;
556   }
557 
558   /* Memory for doing local proc's work */
559   {
560     PetscInt M_BPB_imax = 0;
561 #if defined(PETSC_USE_CTABLE)
562     ierr = PetscIntMultError((M/PETSC_BITS_PER_BYTE+1),imax, &M_BPB_imax);CHKERRQ(ierr);
563     ierr = PetscMalloc1(imax,&table_data);CHKERRQ(ierr);
564     for (i=0; i<imax; i++) {
565       ierr = PetscTableCreate(n[i]+1,M+1,&table_data[i]);CHKERRQ(ierr);
566     }
567     ierr = PetscCalloc4(imax,&table, imax,&data, imax,&isz, M_BPB_imax,&t_p);CHKERRQ(ierr);
568     for (i=0; i<imax; i++) {
569       table[i] = t_p + (M/PETSC_BITS_PER_BYTE+1)*i;
570     }
571 #else
572     PetscInt Mimax = 0;
573     ierr = PetscIntMultError(M,imax, &Mimax);CHKERRQ(ierr);
574     ierr = PetscIntMultError((M/PETSC_BITS_PER_BYTE+1),imax, &M_BPB_imax);CHKERRQ(ierr);
575     ierr = PetscCalloc5(imax,&table, imax,&data, imax,&isz, Mimax,&d_p, M_BPB_imax,&t_p);CHKERRQ(ierr);
576     for (i=0; i<imax; i++) {
577       table[i] = t_p + (M/PETSC_BITS_PER_BYTE+1)*i;
578       data[i]  = d_p + M*i;
579     }
580 #endif
581   }
582 
583   /* Parse the IS and update local tables and the outgoing buf with the data */
584   {
585     PetscInt n_i,isz_i,*outdat_j,ctr_j;
586     PetscBT  table_i;
587 
588     for (i=0; i<imax; i++) {
589       ierr    = PetscMemzero(ctr,size*sizeof(PetscInt));CHKERRQ(ierr);
590       n_i     = n[i];
591       table_i = table[i];
592       idx_i   = idx[i];
593 #if defined(PETSC_USE_CTABLE)
594       table_data_i = table_data[i];
595 #else
596       data_i  = data[i];
597 #endif
598       isz_i   = isz[i];
599       for (j=0; j<n_i; j++) {   /* parse the indices of each IS */
600         row  = idx_i[j];
601         ierr = PetscLayoutFindOwner(C->rmap,row,&proc);CHKERRQ(ierr);
602         if (proc != rank) { /* copy to the outgoing buffer */
603           ctr[proc]++;
604           *ptr[proc] = row;
605           ptr[proc]++;
606         } else if (!PetscBTLookupSet(table_i,row)) {
607 #if defined(PETSC_USE_CTABLE)
608           ierr = PetscTableAdd(table_data_i,row+1,isz_i+1,INSERT_VALUES);CHKERRQ(ierr);
609 #else
610           data_i[isz_i] = row; /* Update the local table */
611 #endif
612           isz_i++;
613         }
614       }
615       /* Update the headers for the current IS */
616       for (j=0; j<size; j++) { /* Can Optimise this loop by using pa[] */
617         if ((ctr_j = ctr[j])) {
618           outdat_j        = outdat[j];
619           k               = ++outdat_j[0];
620           outdat_j[2*k]   = ctr_j;
621           outdat_j[2*k-1] = i;
622         }
623       }
624       isz[i] = isz_i;
625     }
626   }
627 
628   /*  Now  post the sends */
629   ierr = PetscMalloc1(nrqs+1,&s_waits1);CHKERRQ(ierr);
630   for (i=0; i<nrqs; ++i) {
631     j    = pa[i];
632     ierr = MPI_Isend(outdat[j],w1[j],MPIU_INT,j,tag1,comm,s_waits1+i);CHKERRQ(ierr);
633   }
634 
635   /* No longer need the original indices */
636   for (i=0; i<imax; ++i) {
637     ierr = ISRestoreIndices(is[i],idx+i);CHKERRQ(ierr);
638   }
639   ierr = PetscFree2(idx,n);CHKERRQ(ierr);
640 
641   for (i=0; i<imax; ++i) {
642     ierr = ISDestroy(&is[i]);CHKERRQ(ierr);
643   }
644 
645   /* Do Local work */
646 #if defined(PETSC_USE_CTABLE)
647   ierr = MatIncreaseOverlap_MPIAIJ_Local(C,imax,table,isz,NULL,table_data);CHKERRQ(ierr);
648 #else
649   ierr = MatIncreaseOverlap_MPIAIJ_Local(C,imax,table,isz,data,NULL);CHKERRQ(ierr);
650 #endif
651 
652   /* Receive messages */
653   ierr = PetscMalloc1(nrqr+1,&recv_status);CHKERRQ(ierr);
654   if (nrqr) {ierr = MPI_Waitall(nrqr,r_waits1,recv_status);CHKERRQ(ierr);}
655 
656   ierr = PetscMalloc1(nrqs+1,&s_status);CHKERRQ(ierr);
657   if (nrqs) {ierr = MPI_Waitall(nrqs,s_waits1,s_status);CHKERRQ(ierr);}
658 
659   /* Phase 1 sends are complete - deallocate buffers */
660   ierr = PetscFree4(outdat,ptr,tmp,ctr);CHKERRQ(ierr);
661   ierr = PetscFree4(w1,w2,w3,w4);CHKERRQ(ierr);
662 
663   ierr = PetscMalloc1(nrqr+1,&xdata);CHKERRQ(ierr);
664   ierr = PetscMalloc1(nrqr+1,&isz1);CHKERRQ(ierr);
665   ierr = MatIncreaseOverlap_MPIAIJ_Receive(C,nrqr,rbuf,xdata,isz1);CHKERRQ(ierr);
666   ierr = PetscFree(rbuf[0]);CHKERRQ(ierr);
667   ierr = PetscFree(rbuf);CHKERRQ(ierr);
668 
669 
670   /* Send the data back */
671   /* Do a global reduction to know the buffer space req for incoming messages */
672   {
673     PetscMPIInt *rw1;
674 
675     ierr = PetscCalloc1(size,&rw1);CHKERRQ(ierr);
676 
677     for (i=0; i<nrqr; ++i) {
678       proc = recv_status[i].MPI_SOURCE;
679 
680       if (proc != onodes1[i]) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"MPI_SOURCE mismatch");
681       rw1[proc] = isz1[i];
682     }
683     ierr = PetscFree(onodes1);CHKERRQ(ierr);
684     ierr = PetscFree(olengths1);CHKERRQ(ierr);
685 
686     /* Determine the number of messages to expect, their lengths, from from-ids */
687     ierr = PetscGatherMessageLengths(comm,nrqr,nrqs,rw1,&onodes2,&olengths2);CHKERRQ(ierr);
688     ierr = PetscFree(rw1);CHKERRQ(ierr);
689   }
690   /* Now post the Irecvs corresponding to these messages */
691   ierr = PetscPostIrecvInt(comm,tag2,nrqs,onodes2,olengths2,&rbuf2,&r_waits2);CHKERRQ(ierr);
692 
693   /* Now  post the sends */
694   ierr = PetscMalloc1(nrqr+1,&s_waits2);CHKERRQ(ierr);
695   for (i=0; i<nrqr; ++i) {
696     j    = recv_status[i].MPI_SOURCE;
697     ierr = MPI_Isend(xdata[i],isz1[i],MPIU_INT,j,tag2,comm,s_waits2+i);CHKERRQ(ierr);
698   }
699 
700   /* receive work done on other processors */
701   {
702     PetscInt    is_no,ct1,max,*rbuf2_i,isz_i,jmax;
703     PetscMPIInt idex;
704     PetscBT     table_i;
705     MPI_Status  *status2;
706 
707     ierr = PetscMalloc1((PetscMax(nrqr,nrqs)+1),&status2);CHKERRQ(ierr);
708     for (i=0; i<nrqs; ++i) {
709       ierr = MPI_Waitany(nrqs,r_waits2,&idex,status2+i);CHKERRQ(ierr);
710       /* Process the message */
711       rbuf2_i = rbuf2[idex];
712       ct1     = 2*rbuf2_i[0]+1;
713       jmax    = rbuf2[idex][0];
714       for (j=1; j<=jmax; j++) {
715         max     = rbuf2_i[2*j];
716         is_no   = rbuf2_i[2*j-1];
717         isz_i   = isz[is_no];
718         table_i = table[is_no];
719 #if defined(PETSC_USE_CTABLE)
720         table_data_i = table_data[is_no];
721 #else
722         data_i  = data[is_no];
723 #endif
724         for (k=0; k<max; k++,ct1++) {
725           row = rbuf2_i[ct1];
726           if (!PetscBTLookupSet(table_i,row)) {
727 #if defined(PETSC_USE_CTABLE)
728             ierr = PetscTableAdd(table_data_i,row+1,isz_i+1,INSERT_VALUES);CHKERRQ(ierr);
729 #else
730             data_i[isz_i] = row;
731 #endif
732             isz_i++;
733           }
734         }
735         isz[is_no] = isz_i;
736       }
737     }
738 
739     if (nrqr) {ierr = MPI_Waitall(nrqr,s_waits2,status2);CHKERRQ(ierr);}
740     ierr = PetscFree(status2);CHKERRQ(ierr);
741   }
742 
743 #if defined(PETSC_USE_CTABLE)
744   tcount_max = 0;
745   for (i=0; i<imax; ++i) {
746     table_data_i = table_data[i];
747     ierr = PetscTableGetCount(table_data_i,&tcount);CHKERRQ(ierr);
748     if (tcount_max < tcount) tcount_max = tcount;
749   }
750   ierr = PetscMalloc1(tcount_max+1,&tdata);CHKERRQ(ierr);
751 #endif
752 
753   for (i=0; i<imax; ++i) {
754 #if defined(PETSC_USE_CTABLE)
755     PetscTablePosition tpos;
756     table_data_i = table_data[i];
757 
758     ierr = PetscTableGetHeadPosition(table_data_i,&tpos);CHKERRQ(ierr);
759     while (tpos) {
760       ierr = PetscTableGetNext(table_data_i,&tpos,&k,&j);CHKERRQ(ierr);
761       tdata[--j] = --k;
762     }
763     ierr = ISCreateGeneral(PETSC_COMM_SELF,isz[i],tdata,PETSC_COPY_VALUES,is+i);CHKERRQ(ierr);
764 #else
765     ierr = ISCreateGeneral(PETSC_COMM_SELF,isz[i],data[i],PETSC_COPY_VALUES,is+i);CHKERRQ(ierr);
766 #endif
767   }
768 
769   ierr = PetscFree(onodes2);CHKERRQ(ierr);
770   ierr = PetscFree(olengths2);CHKERRQ(ierr);
771 
772   ierr = PetscFree(pa);CHKERRQ(ierr);
773   ierr = PetscFree(rbuf2[0]);CHKERRQ(ierr);
774   ierr = PetscFree(rbuf2);CHKERRQ(ierr);
775   ierr = PetscFree(s_waits1);CHKERRQ(ierr);
776   ierr = PetscFree(r_waits1);CHKERRQ(ierr);
777   ierr = PetscFree(s_waits2);CHKERRQ(ierr);
778   ierr = PetscFree(r_waits2);CHKERRQ(ierr);
779   ierr = PetscFree(s_status);CHKERRQ(ierr);
780   ierr = PetscFree(recv_status);CHKERRQ(ierr);
781   ierr = PetscFree(xdata[0]);CHKERRQ(ierr);
782   ierr = PetscFree(xdata);CHKERRQ(ierr);
783   ierr = PetscFree(isz1);CHKERRQ(ierr);
784 #if defined(PETSC_USE_CTABLE)
785   for (i=0; i<imax; i++) {
786     ierr = PetscTableDestroy((PetscTable*)&table_data[i]);CHKERRQ(ierr);
787   }
788   ierr = PetscFree(table_data);CHKERRQ(ierr);
789   ierr = PetscFree(tdata);CHKERRQ(ierr);
790   ierr = PetscFree4(table,data,isz,t_p);CHKERRQ(ierr);
791 #else
792   ierr = PetscFree5(table,data,isz,d_p,t_p);CHKERRQ(ierr);
793 #endif
794   PetscFunctionReturn(0);
795 }
796 
797 /*
798    MatIncreaseOverlap_MPIAIJ_Local - Called by MatincreaseOverlap, to do
799        the work on the local processor.
800 
801      Inputs:
802       C      - MAT_MPIAIJ;
803       imax - total no of index sets processed at a time;
804       table  - an array of char - size = m bits.
805 
806      Output:
807       isz    - array containing the count of the solution elements corresponding
808                to each index set;
809       data or table_data  - pointer to the solutions
810 */
811 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Local(Mat C,PetscInt imax,PetscBT *table,PetscInt *isz,PetscInt **data,PetscTable *table_data)
812 {
813   Mat_MPIAIJ *c = (Mat_MPIAIJ*)C->data;
814   Mat        A  = c->A,B = c->B;
815   Mat_SeqAIJ *a = (Mat_SeqAIJ*)A->data,*b = (Mat_SeqAIJ*)B->data;
816   PetscInt   start,end,val,max,rstart,cstart,*ai,*aj;
817   PetscInt   *bi,*bj,*garray,i,j,k,row,isz_i;
818   PetscBT    table_i;
819 #if defined(PETSC_USE_CTABLE)
820   PetscTable         table_data_i;
821   PetscErrorCode     ierr;
822   PetscTablePosition tpos;
823   PetscInt           tcount,*tdata;
824 #else
825   PetscInt           *data_i;
826 #endif
827 
828   PetscFunctionBegin;
829   rstart = C->rmap->rstart;
830   cstart = C->cmap->rstart;
831   ai     = a->i;
832   aj     = a->j;
833   bi     = b->i;
834   bj     = b->j;
835   garray = c->garray;
836 
837   for (i=0; i<imax; i++) {
838 #if defined(PETSC_USE_CTABLE)
839     /* copy existing entries of table_data_i into tdata[] */
840     table_data_i = table_data[i];
841     ierr = PetscTableGetCount(table_data_i,&tcount);CHKERRQ(ierr);
842     if (tcount != isz[i]) SETERRQ3(PETSC_COMM_SELF,0," tcount %d != isz[%d] %d",tcount,i,isz[i]);
843 
844     ierr = PetscMalloc1(tcount,&tdata);CHKERRQ(ierr);
845     ierr = PetscTableGetHeadPosition(table_data_i,&tpos);CHKERRQ(ierr);
846     while (tpos) {
847       ierr = PetscTableGetNext(table_data_i,&tpos,&row,&j);CHKERRQ(ierr);
848       tdata[--j] = --row;
849       if (j > tcount - 1) SETERRQ2(PETSC_COMM_SELF,0," j %d >= tcount %d",j,tcount);
850     }
851 #else
852     data_i  = data[i];
853 #endif
854     table_i = table[i];
855     isz_i   = isz[i];
856     max     = isz[i];
857 
858     for (j=0; j<max; j++) {
859 #if defined(PETSC_USE_CTABLE)
860       row   = tdata[j] - rstart;
861 #else
862       row   = data_i[j] - rstart;
863 #endif
864       start = ai[row];
865       end   = ai[row+1];
866       for (k=start; k<end; k++) { /* Amat */
867         val = aj[k] + cstart;
868         if (!PetscBTLookupSet(table_i,val)) {
869 #if defined(PETSC_USE_CTABLE)
870           ierr = PetscTableAdd(table_data_i,val+1,isz_i+1,INSERT_VALUES);CHKERRQ(ierr);
871 #else
872           data_i[isz_i] = val;
873 #endif
874           isz_i++;
875         }
876       }
877       start = bi[row];
878       end   = bi[row+1];
879       for (k=start; k<end; k++) { /* Bmat */
880         val = garray[bj[k]];
881         if (!PetscBTLookupSet(table_i,val)) {
882 #if defined(PETSC_USE_CTABLE)
883           ierr = PetscTableAdd(table_data_i,val+1,isz_i+1,INSERT_VALUES);CHKERRQ(ierr);
884 #else
885           data_i[isz_i] = val;
886 #endif
887           isz_i++;
888         }
889       }
890     }
891     isz[i] = isz_i;
892 
893 #if defined(PETSC_USE_CTABLE)
894     ierr = PetscFree(tdata);CHKERRQ(ierr);
895 #endif
896   }
897   PetscFunctionReturn(0);
898 }
899 
900 /*
901       MatIncreaseOverlap_MPIAIJ_Receive - Process the recieved messages,
902          and return the output
903 
904          Input:
905            C    - the matrix
906            nrqr - no of messages being processed.
907            rbuf - an array of pointers to the recieved requests
908 
909          Output:
910            xdata - array of messages to be sent back
911            isz1  - size of each message
912 
913   For better efficiency perhaps we should malloc separately each xdata[i],
914 then if a remalloc is required we need only copy the data for that one row
915 rather then all previous rows as it is now where a single large chunck of
916 memory is used.
917 
918 */
919 static PetscErrorCode MatIncreaseOverlap_MPIAIJ_Receive(Mat C,PetscInt nrqr,PetscInt **rbuf,PetscInt **xdata,PetscInt * isz1)
920 {
921   Mat_MPIAIJ     *c = (Mat_MPIAIJ*)C->data;
922   Mat            A  = c->A,B = c->B;
923   Mat_SeqAIJ     *a = (Mat_SeqAIJ*)A->data,*b = (Mat_SeqAIJ*)B->data;
924   PetscErrorCode ierr;
925   PetscInt       rstart,cstart,*ai,*aj,*bi,*bj,*garray,i,j,k;
926   PetscInt       row,total_sz,ct,ct1,ct2,ct3,mem_estimate,oct2,l,start,end;
927   PetscInt       val,max1,max2,m,no_malloc =0,*tmp,new_estimate,ctr;
928   PetscInt       *rbuf_i,kmax,rbuf_0;
929   PetscBT        xtable;
930 
931   PetscFunctionBegin;
932   m      = C->rmap->N;
933   rstart = C->rmap->rstart;
934   cstart = C->cmap->rstart;
935   ai     = a->i;
936   aj     = a->j;
937   bi     = b->i;
938   bj     = b->j;
939   garray = c->garray;
940 
941 
942   for (i=0,ct=0,total_sz=0; i<nrqr; ++i) {
943     rbuf_i =  rbuf[i];
944     rbuf_0 =  rbuf_i[0];
945     ct    += rbuf_0;
946     for (j=1; j<=rbuf_0; j++) total_sz += rbuf_i[2*j];
947   }
948 
949   if (C->rmap->n) max1 = ct*(a->nz + b->nz)/C->rmap->n;
950   else max1 = 1;
951   mem_estimate = 3*((total_sz > max1 ? total_sz : max1)+1);
952   ierr         = PetscMalloc1(mem_estimate,&xdata[0]);CHKERRQ(ierr);
953   ++no_malloc;
954   ierr = PetscBTCreate(m,&xtable);CHKERRQ(ierr);
955   ierr = PetscMemzero(isz1,nrqr*sizeof(PetscInt));CHKERRQ(ierr);
956 
957   ct3 = 0;
958   for (i=0; i<nrqr; i++) { /* for easch mesg from proc i */
959     rbuf_i =  rbuf[i];
960     rbuf_0 =  rbuf_i[0];
961     ct1    =  2*rbuf_0+1;
962     ct2    =  ct1;
963     ct3   += ct1;
964     for (j=1; j<=rbuf_0; j++) { /* for each IS from proc i*/
965       ierr = PetscBTMemzero(m,xtable);CHKERRQ(ierr);
966       oct2 = ct2;
967       kmax = rbuf_i[2*j];
968       for (k=0; k<kmax; k++,ct1++) {
969         row = rbuf_i[ct1];
970         if (!PetscBTLookupSet(xtable,row)) {
971           if (!(ct3 < mem_estimate)) {
972             new_estimate = (PetscInt)(1.5*mem_estimate)+1;
973             ierr         = PetscMalloc1(new_estimate,&tmp);CHKERRQ(ierr);
974             ierr         = PetscMemcpy(tmp,xdata[0],mem_estimate*sizeof(PetscInt));CHKERRQ(ierr);
975             ierr         = PetscFree(xdata[0]);CHKERRQ(ierr);
976             xdata[0]     = tmp;
977             mem_estimate = new_estimate; ++no_malloc;
978             for (ctr=1; ctr<=i; ctr++) xdata[ctr] = xdata[ctr-1] + isz1[ctr-1];
979           }
980           xdata[i][ct2++] = row;
981           ct3++;
982         }
983       }
984       for (k=oct2,max2=ct2; k<max2; k++) {
985         row   = xdata[i][k] - rstart;
986         start = ai[row];
987         end   = ai[row+1];
988         for (l=start; l<end; l++) {
989           val = aj[l] + cstart;
990           if (!PetscBTLookupSet(xtable,val)) {
991             if (!(ct3 < mem_estimate)) {
992               new_estimate = (PetscInt)(1.5*mem_estimate)+1;
993               ierr         = PetscMalloc1(new_estimate,&tmp);CHKERRQ(ierr);
994               ierr         = PetscMemcpy(tmp,xdata[0],mem_estimate*sizeof(PetscInt));CHKERRQ(ierr);
995               ierr         = PetscFree(xdata[0]);CHKERRQ(ierr);
996               xdata[0]     = tmp;
997               mem_estimate = new_estimate; ++no_malloc;
998               for (ctr=1; ctr<=i; ctr++) xdata[ctr] = xdata[ctr-1] + isz1[ctr-1];
999             }
1000             xdata[i][ct2++] = val;
1001             ct3++;
1002           }
1003         }
1004         start = bi[row];
1005         end   = bi[row+1];
1006         for (l=start; l<end; l++) {
1007           val = garray[bj[l]];
1008           if (!PetscBTLookupSet(xtable,val)) {
1009             if (!(ct3 < mem_estimate)) {
1010               new_estimate = (PetscInt)(1.5*mem_estimate)+1;
1011               ierr         = PetscMalloc1(new_estimate,&tmp);CHKERRQ(ierr);
1012               ierr         = PetscMemcpy(tmp,xdata[0],mem_estimate*sizeof(PetscInt));CHKERRQ(ierr);
1013               ierr         = PetscFree(xdata[0]);CHKERRQ(ierr);
1014               xdata[0]     = tmp;
1015               mem_estimate = new_estimate; ++no_malloc;
1016               for (ctr =1; ctr <=i; ctr++) xdata[ctr] = xdata[ctr-1] + isz1[ctr-1];
1017             }
1018             xdata[i][ct2++] = val;
1019             ct3++;
1020           }
1021         }
1022       }
1023       /* Update the header*/
1024       xdata[i][2*j]   = ct2 - oct2; /* Undo the vector isz1 and use only a var*/
1025       xdata[i][2*j-1] = rbuf_i[2*j-1];
1026     }
1027     xdata[i][0] = rbuf_0;
1028     xdata[i+1]  = xdata[i] + ct2;
1029     isz1[i]     = ct2; /* size of each message */
1030   }
1031   ierr = PetscBTDestroy(&xtable);CHKERRQ(ierr);
1032   ierr = PetscInfo3(C,"Allocated %D bytes, required %D bytes, no of mallocs = %D\n",mem_estimate,ct3,no_malloc);CHKERRQ(ierr);
1033   PetscFunctionReturn(0);
1034 }
1035 /* -------------------------------------------------------------------------*/
1036 extern PetscErrorCode MatGetSubMatrices_MPIAIJ_Local(Mat,PetscInt,const IS[],const IS[],MatReuse,PetscBool*,Mat*);
1037 extern PetscErrorCode MatAssemblyEnd_SeqAIJ(Mat,MatAssemblyType);
1038 /*
1039     Every processor gets the entire matrix
1040 */
1041 PetscErrorCode MatGetSubMatrix_MPIAIJ_All(Mat A,MatGetSubMatrixOption flag,MatReuse scall,Mat *Bin[])
1042 {
1043   Mat            B;
1044   Mat_MPIAIJ     *a = (Mat_MPIAIJ*)A->data;
1045   Mat_SeqAIJ     *b,*ad = (Mat_SeqAIJ*)a->A->data,*bd = (Mat_SeqAIJ*)a->B->data;
1046   PetscErrorCode ierr;
1047   PetscMPIInt    size,rank,*recvcounts = 0,*displs = 0;
1048   PetscInt       sendcount,i,*rstarts = A->rmap->range,n,cnt,j;
1049   PetscInt       m,*b_sendj,*garray = a->garray,*lens,*jsendbuf,*a_jsendbuf,*b_jsendbuf;
1050   MatScalar      *sendbuf,*recvbuf,*a_sendbuf,*b_sendbuf;
1051 
1052   PetscFunctionBegin;
1053   ierr = MPI_Comm_size(PetscObjectComm((PetscObject)A),&size);CHKERRQ(ierr);
1054   ierr = MPI_Comm_rank(PetscObjectComm((PetscObject)A),&rank);CHKERRQ(ierr);
1055 
1056   if (scall == MAT_INITIAL_MATRIX) {
1057     /* ----------------------------------------------------------------
1058          Tell every processor the number of nonzeros per row
1059     */
1060     ierr = PetscMalloc1(A->rmap->N,&lens);CHKERRQ(ierr);
1061     for (i=A->rmap->rstart; i<A->rmap->rend; i++) {
1062       lens[i] = ad->i[i-A->rmap->rstart+1] - ad->i[i-A->rmap->rstart] + bd->i[i-A->rmap->rstart+1] - bd->i[i-A->rmap->rstart];
1063     }
1064     ierr      = PetscMalloc2(size,&recvcounts,size,&displs);CHKERRQ(ierr);
1065     for (i=0; i<size; i++) {
1066       recvcounts[i] = A->rmap->range[i+1] - A->rmap->range[i];
1067       displs[i]     = A->rmap->range[i];
1068     }
1069 #if defined(PETSC_HAVE_MPI_IN_PLACE)
1070     ierr = MPI_Allgatherv(MPI_IN_PLACE,0,MPI_DATATYPE_NULL,lens,recvcounts,displs,MPIU_INT,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1071 #else
1072     sendcount = A->rmap->rend - A->rmap->rstart;
1073     ierr = MPI_Allgatherv(lens+A->rmap->rstart,sendcount,MPIU_INT,lens,recvcounts,displs,MPIU_INT,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1074 #endif
1075     /* ---------------------------------------------------------------
1076          Create the sequential matrix of the same type as the local block diagonal
1077     */
1078     ierr  = MatCreate(PETSC_COMM_SELF,&B);CHKERRQ(ierr);
1079     ierr  = MatSetSizes(B,A->rmap->N,A->cmap->N,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
1080     ierr  = MatSetBlockSizesFromMats(B,A,A);CHKERRQ(ierr);
1081     ierr  = MatSetType(B,((PetscObject)a->A)->type_name);CHKERRQ(ierr);
1082     ierr  = MatSeqAIJSetPreallocation(B,0,lens);CHKERRQ(ierr);
1083     ierr  = PetscMalloc1(1,Bin);CHKERRQ(ierr);
1084     **Bin = B;
1085     b     = (Mat_SeqAIJ*)B->data;
1086 
1087     /*--------------------------------------------------------------------
1088        Copy my part of matrix column indices over
1089     */
1090     sendcount  = ad->nz + bd->nz;
1091     jsendbuf   = b->j + b->i[rstarts[rank]];
1092     a_jsendbuf = ad->j;
1093     b_jsendbuf = bd->j;
1094     n          = A->rmap->rend - A->rmap->rstart;
1095     cnt        = 0;
1096     for (i=0; i<n; i++) {
1097 
1098       /* put in lower diagonal portion */
1099       m = bd->i[i+1] - bd->i[i];
1100       while (m > 0) {
1101         /* is it above diagonal (in bd (compressed) numbering) */
1102         if (garray[*b_jsendbuf] > A->rmap->rstart + i) break;
1103         jsendbuf[cnt++] = garray[*b_jsendbuf++];
1104         m--;
1105       }
1106 
1107       /* put in diagonal portion */
1108       for (j=ad->i[i]; j<ad->i[i+1]; j++) {
1109         jsendbuf[cnt++] = A->rmap->rstart + *a_jsendbuf++;
1110       }
1111 
1112       /* put in upper diagonal portion */
1113       while (m-- > 0) {
1114         jsendbuf[cnt++] = garray[*b_jsendbuf++];
1115       }
1116     }
1117     if (cnt != sendcount) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Corrupted PETSc matrix: nz given %D actual nz %D",sendcount,cnt);
1118 
1119     /*--------------------------------------------------------------------
1120        Gather all column indices to all processors
1121     */
1122     for (i=0; i<size; i++) {
1123       recvcounts[i] = 0;
1124       for (j=A->rmap->range[i]; j<A->rmap->range[i+1]; j++) {
1125         recvcounts[i] += lens[j];
1126       }
1127     }
1128     displs[0] = 0;
1129     for (i=1; i<size; i++) {
1130       displs[i] = displs[i-1] + recvcounts[i-1];
1131     }
1132 #if defined(PETSC_HAVE_MPI_IN_PLACE)
1133     ierr = MPI_Allgatherv(MPI_IN_PLACE,0,MPI_DATATYPE_NULL,b->j,recvcounts,displs,MPIU_INT,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1134 #else
1135     ierr = MPI_Allgatherv(jsendbuf,sendcount,MPIU_INT,b->j,recvcounts,displs,MPIU_INT,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1136 #endif
1137     /*--------------------------------------------------------------------
1138         Assemble the matrix into useable form (note numerical values not yet set)
1139     */
1140     /* set the b->ilen (length of each row) values */
1141     ierr = PetscMemcpy(b->ilen,lens,A->rmap->N*sizeof(PetscInt));CHKERRQ(ierr);
1142     /* set the b->i indices */
1143     b->i[0] = 0;
1144     for (i=1; i<=A->rmap->N; i++) {
1145       b->i[i] = b->i[i-1] + lens[i-1];
1146     }
1147     ierr = PetscFree(lens);CHKERRQ(ierr);
1148     ierr = MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1149     ierr = MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1150 
1151   } else {
1152     B = **Bin;
1153     b = (Mat_SeqAIJ*)B->data;
1154   }
1155 
1156   /*--------------------------------------------------------------------
1157        Copy my part of matrix numerical values into the values location
1158   */
1159   if (flag == MAT_GET_VALUES) {
1160     sendcount = ad->nz + bd->nz;
1161     sendbuf   = b->a + b->i[rstarts[rank]];
1162     a_sendbuf = ad->a;
1163     b_sendbuf = bd->a;
1164     b_sendj   = bd->j;
1165     n         = A->rmap->rend - A->rmap->rstart;
1166     cnt       = 0;
1167     for (i=0; i<n; i++) {
1168 
1169       /* put in lower diagonal portion */
1170       m = bd->i[i+1] - bd->i[i];
1171       while (m > 0) {
1172         /* is it above diagonal (in bd (compressed) numbering) */
1173         if (garray[*b_sendj] > A->rmap->rstart + i) break;
1174         sendbuf[cnt++] = *b_sendbuf++;
1175         m--;
1176         b_sendj++;
1177       }
1178 
1179       /* put in diagonal portion */
1180       for (j=ad->i[i]; j<ad->i[i+1]; j++) {
1181         sendbuf[cnt++] = *a_sendbuf++;
1182       }
1183 
1184       /* put in upper diagonal portion */
1185       while (m-- > 0) {
1186         sendbuf[cnt++] = *b_sendbuf++;
1187         b_sendj++;
1188       }
1189     }
1190     if (cnt != sendcount) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Corrupted PETSc matrix: nz given %D actual nz %D",sendcount,cnt);
1191 
1192     /* -----------------------------------------------------------------
1193        Gather all numerical values to all processors
1194     */
1195     if (!recvcounts) {
1196       ierr = PetscMalloc2(size,&recvcounts,size,&displs);CHKERRQ(ierr);
1197     }
1198     for (i=0; i<size; i++) {
1199       recvcounts[i] = b->i[rstarts[i+1]] - b->i[rstarts[i]];
1200     }
1201     displs[0] = 0;
1202     for (i=1; i<size; i++) {
1203       displs[i] = displs[i-1] + recvcounts[i-1];
1204     }
1205     recvbuf = b->a;
1206 #if defined(PETSC_HAVE_MPI_IN_PLACE)
1207     ierr = MPI_Allgatherv(MPI_IN_PLACE,0,MPI_DATATYPE_NULL,recvbuf,recvcounts,displs,MPIU_SCALAR,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1208 #else
1209     ierr = MPI_Allgatherv(sendbuf,sendcount,MPIU_SCALAR,recvbuf,recvcounts,displs,MPIU_SCALAR,PetscObjectComm((PetscObject)A));CHKERRQ(ierr);
1210 #endif
1211   }  /* endof (flag == MAT_GET_VALUES) */
1212   ierr = PetscFree2(recvcounts,displs);CHKERRQ(ierr);
1213 
1214   if (A->symmetric) {
1215     ierr = MatSetOption(B,MAT_SYMMETRIC,PETSC_TRUE);CHKERRQ(ierr);
1216   } else if (A->hermitian) {
1217     ierr = MatSetOption(B,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);
1218   } else if (A->structurally_symmetric) {
1219     ierr = MatSetOption(B,MAT_STRUCTURALLY_SYMMETRIC,PETSC_TRUE);CHKERRQ(ierr);
1220   }
1221   PetscFunctionReturn(0);
1222 }
1223 PetscErrorCode MatDestroy_MPIAIJ_MatGetSubmatrices(Mat C)
1224 {
1225   PetscErrorCode ierr;
1226   Mat_SeqAIJ     *c = (Mat_SeqAIJ*)C->data;
1227   Mat_SubMat     *submatj = c->submatis1;
1228   PetscInt       i;
1229 
1230   PetscFunctionBegin;
1231   if (!submatj->id) { /* delete data that are linked only to submats[id=0] */
1232     ierr = PetscFree4(submatj->sbuf1,submatj->ptr,submatj->tmp,submatj->ctr);CHKERRQ(ierr);
1233 
1234     for (i=0; i<submatj->nrqr; ++i) {
1235       ierr = PetscFree(submatj->sbuf2[i]);CHKERRQ(ierr);
1236     }
1237     ierr = PetscFree3(submatj->sbuf2,submatj->req_size,submatj->req_source1);CHKERRQ(ierr);
1238 
1239     if (submatj->rbuf1) {
1240       ierr = PetscFree(submatj->rbuf1[0]);CHKERRQ(ierr);
1241       ierr = PetscFree(submatj->rbuf1);CHKERRQ(ierr);
1242     }
1243 
1244     for (i=0; i<submatj->nrqs; ++i) {
1245       ierr = PetscFree(submatj->rbuf3[i]);CHKERRQ(ierr);
1246     }
1247     ierr = PetscFree3(submatj->req_source2,submatj->rbuf2,submatj->rbuf3);CHKERRQ(ierr);
1248     ierr = PetscFree(submatj->pa);CHKERRQ(ierr);
1249   }
1250 
1251 #if defined(PETSC_USE_CTABLE)
1252   ierr = PetscTableDestroy((PetscTable*)&submatj->rmap);CHKERRQ(ierr);
1253   if (submatj->cmap_loc) {ierr = PetscFree(submatj->cmap_loc);CHKERRQ(ierr);}
1254   ierr = PetscFree(submatj->rmap_loc);CHKERRQ(ierr);
1255 #else
1256   ierr = PetscFree(submatj->rmap);CHKERRQ(ierr);
1257 #endif
1258 
1259   if (!submatj->allcolumns) {
1260 #if defined(PETSC_USE_CTABLE)
1261     ierr = PetscTableDestroy((PetscTable*)&submatj->cmap);CHKERRQ(ierr);
1262 #else
1263     ierr = PetscFree(submatj->cmap);CHKERRQ(ierr);
1264 #endif
1265   }
1266   ierr = submatj->destroy(C);CHKERRQ(ierr);
1267   ierr = PetscFree(submatj->row2proc);CHKERRQ(ierr);
1268 
1269   ierr = PetscFree(submatj);CHKERRQ(ierr);
1270   PetscFunctionReturn(0);
1271 }
1272 
1273 PetscErrorCode MatGetSubMatrices_MPIAIJ_SingleIS_Local(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,PetscBool allcolumns,Mat *submats)
1274 {
1275   Mat_MPIAIJ     *c = (Mat_MPIAIJ*)C->data;
1276   Mat            submat,A = c->A,B = c->B;
1277   Mat_SeqAIJ     *a = (Mat_SeqAIJ*)A->data,*b = (Mat_SeqAIJ*)B->data,*subc;
1278   PetscInt       *ai=a->i,*aj=a->j,*bi=b->i,*bj=b->j,nzA,nzB;
1279   PetscInt       cstart = C->cmap->rstart,cend = C->cmap->rend,rstart = C->rmap->rstart,*bmap = c->garray;
1280   const PetscInt *icol,*irow;
1281   PetscInt       nrow,ncol,start;
1282   PetscErrorCode ierr;
1283   PetscMPIInt    rank,size,tag1,tag2,tag3,tag4,*w1,*w2,nrqr;
1284   PetscInt       **sbuf1,**sbuf2,i,j,k,l,ct1,ct2,ct3,**rbuf1,row,proc;
1285   PetscInt       nrqs=0,msz,**ptr,*req_size,*ctr,*pa,*tmp,tcol,*iptr;
1286   PetscInt       **rbuf3,*req_source1,*req_source2,**sbuf_aj,**rbuf2,max1,nnz;
1287   PetscInt       *lens,rmax,ncols,*cols,Crow;
1288 #if defined(PETSC_USE_CTABLE)
1289   PetscTable     cmap,rmap;
1290   PetscInt       *cmap_loc,*rmap_loc;
1291 #else
1292   PetscInt       *cmap,*rmap;
1293 #endif
1294   PetscInt       ctr_j,*sbuf1_j,*sbuf_aj_i,*rbuf1_i,kmax,*sbuf1_i,*rbuf2_i,*rbuf3_i;
1295   PetscInt       *cworkB,lwrite,*subcols,*row2proc;
1296   PetscScalar    *vworkA,*vworkB,*a_a = a->a,*b_a = b->a,*subvals=NULL;
1297   MPI_Request    *s_waits1,*r_waits1,*s_waits2,*r_waits2,*r_waits3;
1298   MPI_Request    *r_waits4,*s_waits3 = NULL,*s_waits4;
1299   MPI_Status     *r_status1,*r_status2,*s_status1,*s_status3 = NULL,*s_status2;
1300   MPI_Status     *r_status3 = NULL,*r_status4,*s_status4;
1301   MPI_Comm       comm;
1302   PetscScalar    **rbuf4,**sbuf_aa,*vals,*sbuf_aa_i,*rbuf4_i;
1303   PetscMPIInt    *onodes1,*olengths1,idex,end;
1304   Mat_SubMat     *smatis1;
1305   PetscBool      isrowsorted;
1306 
1307   PetscFunctionBegin;
1308   if (ismax != 1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"This routine only works when all processes have ismax=1");
1309 
1310   ierr = PetscObjectGetComm((PetscObject)C,&comm);CHKERRQ(ierr);
1311   size = c->size;
1312   rank = c->rank;
1313 
1314   ierr = ISSorted(isrow[0],&isrowsorted);CHKERRQ(ierr);
1315   if (!isrowsorted) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"isrow[0] must be sorted");
1316 
1317   ierr = ISGetIndices(isrow[0],&irow);CHKERRQ(ierr);
1318   ierr = ISGetLocalSize(isrow[0],&nrow);CHKERRQ(ierr);
1319   if (allcolumns) {
1320     icol = NULL;
1321     ncol = C->cmap->N;
1322   } else {
1323     ierr = ISGetIndices(iscol[0],&icol);CHKERRQ(ierr);
1324     ierr = ISGetLocalSize(iscol[0],&ncol);CHKERRQ(ierr);
1325   }
1326 
1327   if (scall == MAT_INITIAL_MATRIX) {
1328     PetscInt *sbuf2_i,*cworkA,lwrite,ctmp;
1329 
1330     /* Get some new tags to keep the communication clean */
1331     tag1 = ((PetscObject)C)->tag;
1332     ierr = PetscObjectGetNewTag((PetscObject)C,&tag2);CHKERRQ(ierr);
1333     ierr = PetscObjectGetNewTag((PetscObject)C,&tag3);CHKERRQ(ierr);
1334 
1335     /* evaluate communication - mesg to who, length of mesg, and buffer space
1336      required. Based on this, buffers are allocated, and data copied into them */
1337     ierr = PetscCalloc2(size,&w1,size,&w2);CHKERRQ(ierr);
1338     ierr = PetscMalloc1(nrow,&row2proc);CHKERRQ(ierr);
1339 
1340     /* w1[proc] = num of rows owned by proc -- to be requested */
1341     proc = 0;
1342     nrqs = 0; /* num of outgoing messages */
1343     for (j=0; j<nrow; j++) {
1344       row  = irow[j]; /* sorted! */
1345       while (row >= C->rmap->range[proc+1]) proc++;
1346       w1[proc]++;
1347       row2proc[j] = proc; /* map row index to proc */
1348 
1349       if (proc != rank && !w2[proc]) {
1350         w2[proc] = 1; nrqs++;
1351       }
1352     }
1353     w1[rank] = 0;  /* rows owned by self will not be requested */
1354 
1355     ierr = PetscMalloc1(nrqs+1,&pa);CHKERRQ(ierr); /*(proc -array)*/
1356     for (proc=0,j=0; proc<size; proc++) {
1357       if (w1[proc]) { pa[j++] = proc;}
1358     }
1359 
1360     /* Each message would have a header = 1 + 2*(num of IS) + data (here,num of IS = 1) */
1361     msz = 0;              /* total mesg length (for all procs) */
1362     for (i=0; i<nrqs; i++) {
1363       proc      = pa[i];
1364       w1[proc] += 3;
1365       msz      += w1[proc];
1366     }
1367     ierr = PetscInfo2(0,"Number of outgoing messages %D Total message length %D\n",nrqs,msz);CHKERRQ(ierr);
1368 
1369     /* Determine nrqr, the number of messages to expect, their lengths, from from-ids */
1370     /* if w2[proc]=1, a message of length w1[proc] will be sent to proc; */
1371     ierr = PetscGatherNumberOfMessages(comm,w2,w1,&nrqr);CHKERRQ(ierr);
1372 
1373     /* Input: nrqs: nsend; nrqr: nrecv; w1: msg length to be sent;
1374        Output: onodes1: recv node-ids; olengths1: corresponding recv message length */
1375     ierr = PetscGatherMessageLengths(comm,nrqs,nrqr,w1,&onodes1,&olengths1);CHKERRQ(ierr);
1376 
1377     /* Now post the Irecvs corresponding to these messages */
1378     ierr = PetscPostIrecvInt(comm,tag1,nrqr,onodes1,olengths1,&rbuf1,&r_waits1);CHKERRQ(ierr);
1379 
1380     ierr = PetscFree(onodes1);CHKERRQ(ierr);
1381     ierr = PetscFree(olengths1);CHKERRQ(ierr);
1382 
1383     /* Allocate Memory for outgoing messages */
1384     ierr = PetscMalloc4(size,&sbuf1,size,&ptr,2*msz,&tmp,size,&ctr);CHKERRQ(ierr);
1385     ierr = PetscMemzero(sbuf1,size*sizeof(PetscInt*));CHKERRQ(ierr);
1386     ierr = PetscMemzero(ptr,size*sizeof(PetscInt*));CHKERRQ(ierr);
1387 
1388     /* subf1[pa[0]] = tmp, subf1[pa[i]] = subf1[pa[i-1]] + w1[pa[i-1]] */
1389     iptr = tmp;
1390     for (i=0; i<nrqs; i++) {
1391       proc        = pa[i];
1392       sbuf1[proc] = iptr;
1393       iptr       += w1[proc];
1394     }
1395 
1396     /* Form the outgoing messages */
1397     /* Initialize the header space */
1398     for (i=0; i<nrqs; i++) {
1399       proc      = pa[i];
1400       ierr      = PetscMemzero(sbuf1[proc],3*sizeof(PetscInt));CHKERRQ(ierr);
1401       ptr[proc] = sbuf1[proc] + 3;
1402     }
1403 
1404     /* Parse the isrow and copy data into outbuf */
1405     ierr = PetscMemzero(ctr,size*sizeof(PetscInt));CHKERRQ(ierr);
1406     for (j=0; j<nrow; j++) {  /* parse the indices of each IS */
1407       proc = row2proc[j];
1408       if (proc != rank) { /* copy to the outgoing buf*/
1409         *ptr[proc] = irow[j];
1410         ctr[proc]++; ptr[proc]++;
1411       }
1412     }
1413 
1414     /* Update the headers for the current IS */
1415     for (j=0; j<size; j++) { /* Can Optimise this loop too */
1416       if ((ctr_j = ctr[j])) {
1417         sbuf1_j        = sbuf1[j];
1418         k              = ++sbuf1_j[0];
1419         sbuf1_j[2*k]   = ctr_j;
1420         sbuf1_j[2*k-1] = 0;
1421       }
1422     }
1423 
1424     /* Now post the sends */
1425     ierr = PetscMalloc1(nrqs+1,&s_waits1);CHKERRQ(ierr);
1426     for (i=0; i<nrqs; ++i) {
1427       proc = pa[i];
1428       ierr = MPI_Isend(sbuf1[proc],w1[proc],MPIU_INT,proc,tag1,comm,s_waits1+i);CHKERRQ(ierr);
1429     }
1430 
1431     /* Post Receives to capture the buffer size */
1432     ierr = PetscMalloc4(nrqs+1,&r_status2,nrqr+1,&s_waits2,nrqs+1,&r_waits2,nrqr+1,&s_status2);CHKERRQ(ierr);
1433     ierr = PetscMalloc3(nrqs+1,&req_source2,nrqs+1,&rbuf2,nrqs+1,&rbuf3);CHKERRQ(ierr);
1434 
1435     rbuf2[0] = tmp + msz;
1436     for (i=1; i<nrqs; ++i) rbuf2[i] = rbuf2[i-1] + w1[pa[i-1]];
1437 
1438     for (i=0; i<nrqs; ++i) {
1439       proc = pa[i];
1440       ierr = MPI_Irecv(rbuf2[i],w1[proc],MPIU_INT,proc,tag2,comm,r_waits2+i);CHKERRQ(ierr);
1441     }
1442 
1443     ierr = PetscFree2(w1,w2);CHKERRQ(ierr);
1444 
1445     /* Send to other procs the buf size they should allocate */
1446     /* Receive messages*/
1447     ierr = PetscMalloc1(nrqr+1,&r_status1);CHKERRQ(ierr);
1448     ierr = PetscMalloc3(nrqr,&sbuf2,nrqr,&req_size,nrqr,&req_source1);CHKERRQ(ierr);
1449 
1450     ierr = MPI_Waitall(nrqr,r_waits1,r_status1);CHKERRQ(ierr);
1451     for (i=0; i<nrqr; ++i) {
1452       req_size[i] = 0;
1453       rbuf1_i        = rbuf1[i];
1454       start          = 2*rbuf1_i[0] + 1;
1455       ierr           = MPI_Get_count(r_status1+i,MPIU_INT,&end);CHKERRQ(ierr);
1456       ierr           = PetscMalloc1(end+1,&sbuf2[i]);CHKERRQ(ierr);
1457       sbuf2_i        = sbuf2[i];
1458       for (j=start; j<end; j++) {
1459         k            = rbuf1_i[j] - rstart;
1460         ncols        = ai[k+1] - ai[k] + bi[k+1] - bi[k];
1461         sbuf2_i[j]   = ncols;
1462         req_size[i] += ncols;
1463       }
1464       req_source1[i] = r_status1[i].MPI_SOURCE;
1465 
1466       /* form the header */
1467       sbuf2_i[0] = req_size[i];
1468       for (j=1; j<start; j++) sbuf2_i[j] = rbuf1_i[j];
1469 
1470       ierr = MPI_Isend(sbuf2_i,end,MPIU_INT,req_source1[i],tag2,comm,s_waits2+i);CHKERRQ(ierr);
1471     }
1472 
1473     ierr = PetscFree(r_status1);CHKERRQ(ierr);
1474     ierr = PetscFree(r_waits1);CHKERRQ(ierr);
1475 
1476     /* rbuf2 is received, Post recv column indices a->j */
1477     ierr = MPI_Waitall(nrqs,r_waits2,r_status2);CHKERRQ(ierr);
1478 
1479     ierr = PetscMalloc4(nrqs+1,&r_waits3,nrqr+1,&s_waits3,nrqs+1,&r_status3,nrqr+1,&s_status3);CHKERRQ(ierr);
1480     for (i=0; i<nrqs; ++i) {
1481       ierr = PetscMalloc1(rbuf2[i][0]+1,&rbuf3[i]);CHKERRQ(ierr);
1482       req_source2[i] = r_status2[i].MPI_SOURCE;
1483       ierr = MPI_Irecv(rbuf3[i],rbuf2[i][0],MPIU_INT,req_source2[i],tag3,comm,r_waits3+i);CHKERRQ(ierr);
1484     }
1485 
1486     /* Wait on sends1 and sends2 */
1487     ierr = PetscMalloc1(nrqs+1,&s_status1);CHKERRQ(ierr);
1488     ierr = MPI_Waitall(nrqs,s_waits1,s_status1);CHKERRQ(ierr);
1489     ierr = PetscFree(s_waits1);CHKERRQ(ierr);
1490     ierr = PetscFree(s_status1);CHKERRQ(ierr);
1491 
1492     ierr = MPI_Waitall(nrqr,s_waits2,s_status2);CHKERRQ(ierr);
1493     ierr = PetscFree4(r_status2,s_waits2,r_waits2,s_status2);CHKERRQ(ierr);
1494 
1495     /* Now allocate sending buffers for a->j, and send them off */
1496     ierr = PetscMalloc1(nrqr+1,&sbuf_aj);CHKERRQ(ierr);
1497     for (i=0,j=0; i<nrqr; i++) j += req_size[i];
1498     ierr = PetscMalloc1(j+1,&sbuf_aj[0]);CHKERRQ(ierr);
1499     for (i=1; i<nrqr; i++) sbuf_aj[i] = sbuf_aj[i-1] + req_size[i-1];
1500 
1501     for (i=0; i<nrqr; i++) { /* for each requested message */
1502       rbuf1_i   = rbuf1[i];
1503       sbuf_aj_i = sbuf_aj[i];
1504       ct1       = 2*rbuf1_i[0] + 1;
1505       ct2       = 0;
1506       /* max1=rbuf1_i[0]; if (max1 != 1) SETERRQ1(PETSC_COMM_SELF,0,"max1 %d != 1",max1); */
1507 
1508       kmax = rbuf1[i][2];
1509       for (k=0; k<kmax; k++,ct1++) { /* for each row */
1510         row    = rbuf1_i[ct1] - rstart;
1511         nzA    = ai[row+1] - ai[row];
1512         nzB    = bi[row+1] - bi[row];
1513         ncols  = nzA + nzB;
1514         cworkA = aj + ai[row]; cworkB = bj + bi[row];
1515 
1516         /* load the column indices for this row into cols*/
1517         cols = sbuf_aj_i + ct2;
1518 
1519         lwrite = 0;
1520         for (l=0; l<nzB; l++) {
1521           if ((ctmp = bmap[cworkB[l]]) < cstart) cols[lwrite++] = ctmp;
1522         }
1523         for (l=0; l<nzA; l++) cols[lwrite++] = cstart + cworkA[l];
1524         for (l=0; l<nzB; l++) {
1525           if ((ctmp = bmap[cworkB[l]]) >= cend) cols[lwrite++] = ctmp;
1526         }
1527 
1528         ct2 += ncols;
1529       }
1530       ierr = MPI_Isend(sbuf_aj_i,req_size[i],MPIU_INT,req_source1[i],tag3,comm,s_waits3+i);CHKERRQ(ierr);
1531     }
1532 
1533     /* create column map (cmap): global col of C -> local col of submat */
1534 #if defined(PETSC_USE_CTABLE)
1535     if (!allcolumns) {
1536       ierr = PetscTableCreate(ncol+1,C->cmap->N+1,&cmap);CHKERRQ(ierr);
1537       ierr = PetscCalloc1(C->cmap->n,&cmap_loc);CHKERRQ(ierr);
1538       for (j=0; j<ncol; j++) { /* use array cmap_loc[] for local col indices */
1539         if (icol[j] >= cstart && icol[j] <cend) {
1540           cmap_loc[icol[j] - cstart] = j+1;
1541         } else { /* use PetscTable for non-local col indices */
1542           ierr = PetscTableAdd(cmap,icol[j]+1,j+1,INSERT_VALUES);CHKERRQ(ierr);
1543         }
1544       }
1545     } else {
1546       cmap     = NULL;
1547       cmap_loc = NULL;
1548     }
1549     ierr = PetscCalloc1(C->rmap->n,&rmap_loc);CHKERRQ(ierr);
1550 #else
1551     if (!allcolumns) {
1552       ierr   = PetscCalloc1(C->cmap->N,&cmap);CHKERRQ(ierr);
1553       for (j=0; j<ncol; j++) cmap[icol[j]] = j+1;
1554     } else {
1555       cmap = NULL;
1556     }
1557 #endif
1558 
1559     /* Create lens for MatSeqAIJSetPreallocation() */
1560     ierr = PetscCalloc1(nrow,&lens);CHKERRQ(ierr);
1561 
1562     /* Compute lens from local part of C */
1563     for (j=0; j<nrow; j++) {
1564       row  = irow[j];
1565       proc = row2proc[j];
1566       if (proc == rank) {
1567         /* diagonal part A = c->A */
1568         ncols = ai[row-rstart+1] - ai[row-rstart];
1569         cols  = aj + ai[row-rstart];
1570         if (!allcolumns) {
1571           for (k=0; k<ncols; k++) {
1572 #if defined(PETSC_USE_CTABLE)
1573             tcol = cmap_loc[cols[k]];
1574 #else
1575             tcol = cmap[cols[k]+cstart];
1576 #endif
1577             if (tcol) lens[j]++;
1578           }
1579         } else { /* allcolumns */
1580           lens[j] = ncols;
1581         }
1582 
1583         /* off-diagonal part B = c->B */
1584         ncols = bi[row-rstart+1] - bi[row-rstart];
1585         cols  = bj + bi[row-rstart];
1586         if (!allcolumns) {
1587           for (k=0; k<ncols; k++) {
1588 #if defined(PETSC_USE_CTABLE)
1589             ierr = PetscTableFind(cmap,bmap[cols[k]]+1,&tcol);CHKERRQ(ierr);
1590 #else
1591             tcol = cmap[bmap[cols[k]]];
1592 #endif
1593             if (tcol) lens[j]++;
1594           }
1595         } else { /* allcolumns */
1596           lens[j] += ncols;
1597         }
1598       }
1599     }
1600 
1601     /* Create row map (rmap): global row of C -> local row of submat */
1602 #if defined(PETSC_USE_CTABLE)
1603     ierr = PetscTableCreate(nrow+1,C->rmap->N+1,&rmap);CHKERRQ(ierr);
1604     for (j=0; j<nrow; j++) {
1605       row  = irow[j];
1606       proc = row2proc[j];
1607       if (proc == rank) { /* a local row */
1608         rmap_loc[row - rstart] = j;
1609       } else {
1610         ierr = PetscTableAdd(rmap,irow[j]+1,j+1,INSERT_VALUES);CHKERRQ(ierr);
1611       }
1612     }
1613 #else
1614     ierr = PetscCalloc1(C->rmap->N,&rmap);CHKERRQ(ierr);
1615     for (j=0; j<nrow; j++) {
1616       rmap[irow[j]] = j;
1617     }
1618 #endif
1619 
1620     /* Update lens from offproc data */
1621     /* recv a->j is done */
1622     ierr    = MPI_Waitall(nrqs,r_waits3,r_status3);CHKERRQ(ierr);
1623     for (i=0; i<nrqs; i++) {
1624       proc    = pa[i];
1625       sbuf1_i = sbuf1[proc];
1626       /* jmax    = sbuf1_i[0]; if (jmax != 1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"jmax !=1"); */
1627       ct1     = 2 + 1;
1628       ct2     = 0;
1629       rbuf2_i = rbuf2[i]; /* received length of C->j */
1630       rbuf3_i = rbuf3[i]; /* received C->j */
1631 
1632       /* is_no  = sbuf1_i[2*j-1]; if (is_no != 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"is_no !=0"); */
1633       max1   = sbuf1_i[2];
1634       for (k=0; k<max1; k++,ct1++) {
1635 #if defined(PETSC_USE_CTABLE)
1636         ierr = PetscTableFind(rmap,sbuf1_i[ct1]+1,&row);CHKERRQ(ierr);
1637         row--;
1638         if (row < 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"row not found in table");
1639 #else
1640         row = rmap[sbuf1_i[ct1]]; /* the row index in submat */
1641 #endif
1642         /* Now, store row index of submat in sbuf1_i[ct1] */
1643         sbuf1_i[ct1] = row;
1644 
1645         nnz = rbuf2_i[ct1];
1646         if (!allcolumns) {
1647           for (l=0; l<nnz; l++,ct2++) {
1648 #if defined(PETSC_USE_CTABLE)
1649             if (rbuf3_i[ct2] >= cstart && rbuf3_i[ct2] <cend) {
1650               tcol = cmap_loc[rbuf3_i[ct2] - cstart];
1651             } else {
1652               ierr = PetscTableFind(cmap,rbuf3_i[ct2]+1,&tcol);CHKERRQ(ierr);
1653             }
1654 #else
1655             tcol = cmap[rbuf3_i[ct2]]; /* column index in submat */
1656 #endif
1657             if (tcol) lens[row]++;
1658           }
1659         } else { /* allcolumns */
1660           lens[row] += nnz;
1661         }
1662       }
1663     }
1664     ierr = MPI_Waitall(nrqr,s_waits3,s_status3);CHKERRQ(ierr);
1665     ierr = PetscFree4(r_waits3,s_waits3,r_status3,s_status3);CHKERRQ(ierr);
1666 
1667     /* Create the submatrices */
1668     ierr = MatCreate(PETSC_COMM_SELF,&submat);CHKERRQ(ierr);
1669     ierr = MatSetSizes(submat,nrow,ncol,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
1670 
1671     ierr = ISGetBlockSize(isrow[0],&i);CHKERRQ(ierr);
1672     ierr = ISGetBlockSize(iscol[0],&j);CHKERRQ(ierr);
1673     ierr = MatSetBlockSizes(submat,i,j);CHKERRQ(ierr);
1674     ierr = MatSetType(submat,((PetscObject)A)->type_name);CHKERRQ(ierr);
1675     ierr = MatSeqAIJSetPreallocation(submat,0,lens);CHKERRQ(ierr);
1676 
1677     /* create struct Mat_SubMat and attached it to submat */
1678     ierr = PetscNew(&smatis1);CHKERRQ(ierr);
1679     subc = (Mat_SeqAIJ*)submat->data;
1680     subc->submatis1 = smatis1;
1681 
1682     smatis1->id          = 0;
1683     smatis1->nrqs        = nrqs;
1684     smatis1->nrqr        = nrqr;
1685     smatis1->rbuf1       = rbuf1;
1686     smatis1->rbuf2       = rbuf2;
1687     smatis1->rbuf3       = rbuf3;
1688     smatis1->sbuf2       = sbuf2;
1689     smatis1->req_source2 = req_source2;
1690 
1691     smatis1->sbuf1       = sbuf1;
1692     smatis1->ptr         = ptr;
1693     smatis1->tmp         = tmp;
1694     smatis1->ctr         = ctr;
1695 
1696     smatis1->pa           = pa;
1697     smatis1->req_size     = req_size;
1698     smatis1->req_source1  = req_source1;
1699 
1700     smatis1->allcolumns  = allcolumns;
1701     smatis1->row2proc    = row2proc;
1702     smatis1->rmap        = rmap;
1703     smatis1->cmap        = cmap;
1704 #if defined(PETSC_USE_CTABLE)
1705     smatis1->rmap_loc    = rmap_loc;
1706     smatis1->cmap_loc    = cmap_loc;
1707 #endif
1708 
1709     smatis1->destroy     = submat->ops->destroy;
1710     submat->ops->destroy = MatDestroy_MPIAIJ_MatGetSubmatrices;
1711     submat->factortype   = C->factortype;
1712 
1713     /* compute rmax */
1714     rmax = 0;
1715     for (i=0; i<nrow; i++) rmax = PetscMax(rmax,lens[i]);
1716 
1717   } else { /* scall == MAT_REUSE_MATRIX */
1718     submat = submats[0];
1719     if (submat->rmap->n != nrow || submat->cmap->n != ncol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Cannot reuse matrix. wrong size");
1720 
1721     subc    = (Mat_SeqAIJ*)submat->data;
1722     rmax    = subc->rmax;
1723     smatis1 = subc->submatis1;
1724     nrqs        = smatis1->nrqs;
1725     nrqr        = smatis1->nrqr;
1726     rbuf1       = smatis1->rbuf1;
1727     rbuf2       = smatis1->rbuf2;
1728     rbuf3       = smatis1->rbuf3;
1729     req_source2 = smatis1->req_source2;
1730 
1731     sbuf1     = smatis1->sbuf1;
1732     sbuf2     = smatis1->sbuf2;
1733     ptr       = smatis1->ptr;
1734     tmp       = smatis1->tmp;
1735     ctr       = smatis1->ctr;
1736 
1737     pa         = smatis1->pa;
1738     req_size   = smatis1->req_size;
1739     req_source1 = smatis1->req_source1;
1740 
1741     allcolumns = smatis1->allcolumns;
1742     row2proc   = smatis1->row2proc;
1743     rmap       = smatis1->rmap;
1744     cmap       = smatis1->cmap;
1745 #if defined(PETSC_USE_CTABLE)
1746     rmap_loc   = smatis1->rmap_loc;
1747     cmap_loc   = smatis1->cmap_loc;
1748 #endif
1749   }
1750 
1751   /* Post recv matrix values */
1752   ierr = PetscMalloc3(nrqs+1,&rbuf4, rmax,&subcols, rmax,&subvals);CHKERRQ(ierr);
1753   ierr = PetscMalloc4(nrqs+1,&r_waits4,nrqr+1,&s_waits4,nrqs+1,&r_status4,nrqr+1,&s_status4);CHKERRQ(ierr);
1754   ierr = PetscObjectGetNewTag((PetscObject)C,&tag4);CHKERRQ(ierr);
1755   for (i=0; i<nrqs; ++i) {
1756     ierr = PetscMalloc1(rbuf2[i][0]+1,&rbuf4[i]);CHKERRQ(ierr);
1757     ierr = MPI_Irecv(rbuf4[i],rbuf2[i][0],MPIU_SCALAR,req_source2[i],tag4,comm,r_waits4+i);CHKERRQ(ierr);
1758   }
1759 
1760   /* Allocate sending buffers for a->a, and send them off */
1761   ierr = PetscMalloc1(nrqr+1,&sbuf_aa);CHKERRQ(ierr);
1762   for (i=0,j=0; i<nrqr; i++) j += req_size[i];
1763   ierr = PetscMalloc1(j+1,&sbuf_aa[0]);CHKERRQ(ierr);
1764   for (i=1; i<nrqr; i++) sbuf_aa[i] = sbuf_aa[i-1] + req_size[i-1];
1765 
1766   for (i=0; i<nrqr; i++) {
1767     rbuf1_i   = rbuf1[i];
1768     sbuf_aa_i = sbuf_aa[i];
1769     ct1       = 2*rbuf1_i[0]+1;
1770     ct2       = 0;
1771     /* max1=rbuf1_i[0]; if (max1 != 1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"max1 !=1"); */
1772 
1773     kmax = rbuf1_i[2];
1774     for (k=0; k<kmax; k++,ct1++) {
1775       row = rbuf1_i[ct1] - rstart;
1776       nzA = ai[row+1] - ai[row];
1777       nzB = bi[row+1] - bi[row];
1778       ncols  = nzA + nzB;
1779       cworkB = bj + bi[row];
1780       vworkA = a_a + ai[row];
1781       vworkB = b_a + bi[row];
1782 
1783       /* load the column values for this row into vals*/
1784       vals = sbuf_aa_i + ct2;
1785 
1786       lwrite = 0;
1787       for (l=0; l<nzB; l++) {
1788         if ((bmap[cworkB[l]]) < cstart) vals[lwrite++] = vworkB[l];
1789       }
1790       for (l=0; l<nzA; l++) vals[lwrite++] = vworkA[l];
1791       for (l=0; l<nzB; l++) {
1792         if ((bmap[cworkB[l]]) >= cend) vals[lwrite++] = vworkB[l];
1793       }
1794 
1795       ct2 += ncols;
1796     }
1797     ierr = MPI_Isend(sbuf_aa_i,req_size[i],MPIU_SCALAR,req_source1[i],tag4,comm,s_waits4+i);CHKERRQ(ierr);
1798   }
1799 
1800   /* Assemble submat */
1801   /* First assemble the local rows */
1802   for (j=0; j<nrow; j++) {
1803     row  = irow[j];
1804     proc = row2proc[j];
1805     if (proc == rank) {
1806       Crow = row - rstart;  /* local row index of C */
1807 #if defined(PETSC_USE_CTABLE)
1808       row = rmap_loc[Crow]; /* row index of submat */
1809 #else
1810       row = rmap[row];
1811 #endif
1812 
1813       if (allcolumns) {
1814         /* diagonal part A = c->A */
1815         ncols = ai[Crow+1] - ai[Crow];
1816         cols  = aj + ai[Crow];
1817         vals  = a->a + ai[Crow];
1818         i     = 0;
1819         for (k=0; k<ncols; k++) {
1820           subcols[i]   = cols[k] + cstart;
1821           subvals[i++] = vals[k];
1822         }
1823 
1824         /* off-diagonal part B = c->B */
1825         ncols = bi[Crow+1] - bi[Crow];
1826         cols  = bj + bi[Crow];
1827         vals  = b->a + bi[Crow];
1828         for (k=0; k<ncols; k++) {
1829           subcols[i]   = bmap[cols[k]];
1830           subvals[i++] = vals[k];
1831         }
1832 
1833         ierr = MatSetValues_SeqAIJ(submat,1,&row,i,subcols,subvals,INSERT_VALUES);CHKERRQ(ierr);
1834 
1835       } else { /* !allcolumns */
1836 #if defined(PETSC_USE_CTABLE)
1837         /* diagonal part A = c->A */
1838         ncols = ai[Crow+1] - ai[Crow];
1839         cols  = aj + ai[Crow];
1840         vals  = a->a + ai[Crow];
1841         i     = 0;
1842         for (k=0; k<ncols; k++) {
1843           tcol = cmap_loc[cols[k]];
1844           if (tcol) {
1845             subcols[i]   = --tcol;
1846             subvals[i++] = vals[k];
1847           }
1848         }
1849 
1850         /* off-diagonal part B = c->B */
1851         ncols = bi[Crow+1] - bi[Crow];
1852         cols  = bj + bi[Crow];
1853         vals  = b->a + bi[Crow];
1854         for (k=0; k<ncols; k++) {
1855           ierr = PetscTableFind(cmap,bmap[cols[k]]+1,&tcol);CHKERRQ(ierr);
1856           if (tcol) {
1857             subcols[i]   = --tcol;
1858             subvals[i++] = vals[k];
1859           }
1860         }
1861 #else
1862         /* diagonal part A = c->A */
1863         ncols = ai[Crow+1] - ai[Crow];
1864         cols  = aj + ai[Crow];
1865         vals  = a->a + ai[Crow];
1866         i     = 0;
1867         for (k=0; k<ncols; k++) {
1868           tcol = cmap[cols[k]+cstart];
1869           if (tcol) {
1870             subcols[i]   = --tcol;
1871             subvals[i++] = vals[k];
1872           }
1873         }
1874 
1875         /* off-diagonal part B = c->B */
1876         ncols = bi[Crow+1] - bi[Crow];
1877         cols  = bj + bi[Crow];
1878         vals  = b->a + bi[Crow];
1879         for (k=0; k<ncols; k++) {
1880           tcol = cmap[bmap[cols[k]]];
1881           if (tcol) {
1882             subcols[i]   = --tcol;
1883             subvals[i++] = vals[k];
1884           }
1885         }
1886 #endif
1887         ierr = MatSetValues_SeqAIJ(submat,1,&row,i,subcols,subvals,INSERT_VALUES);CHKERRQ(ierr);
1888       }
1889     }
1890   }
1891 
1892   /* Now assemble the off-proc rows */
1893   for (i=0; i<nrqs; i++) { /* for each requested message */
1894     /* recv values from other processes */
1895     ierr    = MPI_Waitany(nrqs,r_waits4,&idex,r_status4+i);CHKERRQ(ierr);
1896     proc    = pa[idex];
1897     sbuf1_i = sbuf1[proc];
1898     /* jmax    = sbuf1_i[0]; if (jmax != 1)SETERRQ1(PETSC_COMM_SELF,0,"jmax %d != 1",jmax); */
1899     ct1     = 2 + 1;
1900     ct2     = 0; /* count of received C->j */
1901     ct3     = 0; /* count of received C->j that will be inserted into submat */
1902     rbuf2_i = rbuf2[idex]; /* int** received length of C->j from other processes */
1903     rbuf3_i = rbuf3[idex]; /* int** received C->j from other processes */
1904     rbuf4_i = rbuf4[idex]; /* scalar** received C->a from other processes */
1905 
1906     /* is_no = sbuf1_i[2*j-1]; if (is_no != 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"is_no !=0"); */
1907     max1 = sbuf1_i[2];             /* num of rows */
1908     for (k=0; k<max1; k++,ct1++) { /* for each recved row */
1909       row = sbuf1_i[ct1]; /* row index of submat */
1910       if (!allcolumns) {
1911         idex = 0;
1912         if (scall == MAT_INITIAL_MATRIX) {
1913           nnz  = rbuf2_i[ct1]; /* num of C entries in this row */
1914           for (l=0; l<nnz; l++,ct2++) { /* for each recved column */
1915 #if defined(PETSC_USE_CTABLE)
1916             if (rbuf3_i[ct2] >= cstart && rbuf3_i[ct2] <cend) {
1917               tcol = cmap_loc[rbuf3_i[ct2] - cstart];
1918             } else {
1919               ierr = PetscTableFind(cmap,rbuf3_i[ct2]+1,&tcol);CHKERRQ(ierr);
1920             }
1921 #else
1922             tcol = cmap[rbuf3_i[ct2]];
1923 #endif
1924             if (tcol) {
1925               subcols[idex]   = --tcol;
1926               subvals[idex++] = rbuf4_i[ct2];
1927 
1928               /* We receive an entire column of C, but a subset of it needs to be inserted into submat.
1929                For reuse, we replace received C->j with index that should be inserted to submat */
1930               rbuf3_i[ct3++] = ct2;
1931             }
1932           }
1933           ierr = MatSetValues_SeqAIJ(submat,1,&row,idex,subcols,subvals,INSERT_VALUES);CHKERRQ(ierr);
1934 
1935         } else { /* scall == MAT_REUSE_MATRIX */
1936           submat = submats[0];
1937           subc   = (Mat_SeqAIJ*)submat->data;
1938 
1939           nnz = subc->i[row+1] - subc->i[row]; /* num of submat entries in this row */
1940           for (l=0; l<nnz; l++) {
1941             ct2 = rbuf3_i[ct3++]; /* index of rbuf4_i[] which needs to be inserted into submat */
1942             subvals[idex++] = rbuf4_i[ct2];
1943           }
1944 
1945           bj = subc->j + subc->i[row];
1946           ierr = MatSetValues_SeqAIJ(submat,1,&row,nnz,bj,subvals,INSERT_VALUES);CHKERRQ(ierr);
1947         }
1948       } else { /* allcolumns */
1949         nnz  = rbuf2_i[ct1]; /* num of C entries in this row */
1950         ierr = MatSetValues_SeqAIJ(submat,1,&row,nnz,rbuf3_i+ct2,rbuf4_i+ct2,INSERT_VALUES);CHKERRQ(ierr);
1951         ct2 += nnz;
1952       }
1953     }
1954   }
1955 
1956   /* sending a->a are done */
1957   ierr = MPI_Waitall(nrqr,s_waits4,s_status4);CHKERRQ(ierr);
1958   ierr = PetscFree4(r_waits4,s_waits4,r_status4,s_status4);CHKERRQ(ierr);
1959 
1960   ierr = MatAssemblyBegin(submat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1961   ierr = MatAssemblyEnd(submat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1962   submats[0] = submat;
1963 
1964   /* Restore the indices */
1965   ierr = ISRestoreIndices(isrow[0],&irow);CHKERRQ(ierr);
1966   if (!allcolumns) {
1967     ierr = ISRestoreIndices(iscol[0],&icol);CHKERRQ(ierr);
1968   }
1969 
1970   /* Destroy allocated memory */
1971   for (i=0; i<nrqs; ++i) {
1972     ierr = PetscFree3(rbuf4[i],subcols,subvals);CHKERRQ(ierr);
1973   }
1974   ierr = PetscFree3(rbuf4,subcols,subvals);CHKERRQ(ierr);
1975   ierr = PetscFree(sbuf_aa[0]);CHKERRQ(ierr);
1976   ierr = PetscFree(sbuf_aa);CHKERRQ(ierr);
1977 
1978   if (scall == MAT_INITIAL_MATRIX) {
1979     ierr = PetscFree(lens);CHKERRQ(ierr);
1980     ierr = PetscFree(sbuf_aj[0]);CHKERRQ(ierr);
1981     ierr = PetscFree(sbuf_aj);CHKERRQ(ierr);
1982   }
1983   PetscFunctionReturn(0);
1984 }
1985 
1986 PetscErrorCode MatGetSubMatrices_MPIAIJ_SingleIS(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,Mat *submat[])
1987 {
1988   PetscErrorCode ierr;
1989   PetscInt       ncol;
1990   PetscBool      colflag,allcolumns=PETSC_FALSE;
1991 
1992   PetscFunctionBegin;
1993   /* Allocate memory to hold all the submatrices */
1994   if (scall == MAT_INITIAL_MATRIX) {
1995     ierr = PetscMalloc1(1,submat);CHKERRQ(ierr);
1996   }
1997 
1998   /* Check for special case: each processor gets entire matrix columns */
1999   ierr = ISIdentity(iscol[0],&colflag);CHKERRQ(ierr);
2000   ierr = ISGetLocalSize(iscol[0],&ncol);CHKERRQ(ierr);
2001   if (colflag && ncol == C->cmap->N) allcolumns = PETSC_TRUE;
2002 
2003   ierr = MatGetSubMatrices_MPIAIJ_SingleIS_Local(C,ismax,isrow,iscol,scall,allcolumns,*submat);CHKERRQ(ierr);
2004   PetscFunctionReturn(0);
2005 }
2006 
2007 PetscErrorCode MatGetSubMatrices_MPIAIJ(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,Mat *submat[])
2008 {
2009   PetscErrorCode ierr;
2010   PetscInt       nmax,nstages_local,nstages,i,pos,max_no,nrow,ncol;
2011   PetscBool      rowflag,colflag,wantallmatrix=PETSC_FALSE,twantallmatrix,*allcolumns;
2012 
2013   PetscFunctionBegin;
2014 #if 0
2015   /* Check for special case: each processor gets entire matrix */
2016   if (C->submat_singleis) { /* flag is set in PCSetUp_ASM() to skip several MPIU_Allreduce() */
2017     ierr = MatGetSubMatrices_MPIAIJ_SingleIS(C,ismax,isrow,iscol,scall,submat);CHKERRQ(ierr);
2018     PetscFunctionReturn(0);
2019   }
2020 #endif
2021 
2022   if (ismax == 1 && C->rmap->N == C->cmap->N) {
2023     ierr = ISIdentity(*isrow,&rowflag);CHKERRQ(ierr);
2024     ierr = ISIdentity(*iscol,&colflag);CHKERRQ(ierr);
2025     ierr = ISGetLocalSize(*isrow,&nrow);CHKERRQ(ierr);
2026     ierr = ISGetLocalSize(*iscol,&ncol);CHKERRQ(ierr);
2027     if (rowflag && colflag && nrow == C->rmap->N && ncol == C->cmap->N) {
2028       wantallmatrix = PETSC_TRUE;
2029 
2030       ierr = PetscOptionsGetBool(((PetscObject)C)->options,((PetscObject)C)->prefix,"-use_fast_submatrix",&wantallmatrix,NULL);CHKERRQ(ierr);
2031     }
2032   }
2033   ierr = MPIU_Allreduce(&wantallmatrix,&twantallmatrix,1,MPIU_BOOL,MPI_MIN,PetscObjectComm((PetscObject)C));CHKERRQ(ierr);
2034   if (twantallmatrix) {
2035     ierr = MatGetSubMatrix_MPIAIJ_All(C,MAT_GET_VALUES,scall,submat);CHKERRQ(ierr);
2036     PetscFunctionReturn(0);
2037   }
2038 
2039   /* Allocate memory to hold all the submatrices */
2040   if (scall == MAT_INITIAL_MATRIX) {
2041     ierr = PetscMalloc1(ismax+1,submat);CHKERRQ(ierr);
2042   }
2043 
2044   if (scall == MAT_REUSE_MATRIX && !ismax) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"n=0 is not supported for MatGetSubMatrices(mat,n,isrow,iscol,MAT_REUSE_MATRIX,...). Set n=1 with zero-length isrow and iscolumn instead");
2045 
2046   /* Check for special case: each processor gets entire matrix columns */
2047   ierr = PetscMalloc1(ismax+1,&allcolumns);CHKERRQ(ierr);
2048   for (i=0; i<ismax; i++) {
2049     ierr = ISIdentity(iscol[i],&colflag);CHKERRQ(ierr);
2050     ierr = ISGetLocalSize(iscol[i],&ncol);CHKERRQ(ierr);
2051     if (colflag && ncol == C->cmap->N) {
2052       allcolumns[i] = PETSC_TRUE;
2053     } else {
2054       allcolumns[i] = PETSC_FALSE;
2055     }
2056   }
2057 
2058   /* Determine the number of stages through which submatrices are done */
2059   nmax = 20*1000000 / (C->cmap->N * sizeof(PetscInt));
2060 
2061   /*
2062      Each stage will extract nmax submatrices.
2063      nmax is determined by the matrix column dimension.
2064      If the original matrix has 20M columns, only one submatrix per stage is allowed, etc.
2065   */
2066   if (!nmax) nmax = 1;
2067   nstages_local = ismax/nmax + ((ismax % nmax) ? 1 : 0);
2068 
2069   /* Make sure every processor loops through the nstages */
2070   ierr = MPIU_Allreduce(&nstages_local,&nstages,1,MPIU_INT,MPI_MAX,PetscObjectComm((PetscObject)C));CHKERRQ(ierr);
2071 
2072   for (i=0,pos=0; i<nstages; i++) {
2073     if (pos+nmax <= ismax) max_no = nmax;
2074     else if (pos == ismax) max_no = 0;
2075     else                   max_no = ismax-pos;
2076     ierr = MatGetSubMatrices_MPIAIJ_Local(C,max_no,isrow+pos,iscol+pos,scall,allcolumns+pos,*submat+pos);CHKERRQ(ierr);
2077     pos += max_no;
2078   }
2079 
2080   ierr = PetscFree(allcolumns);CHKERRQ(ierr);
2081   PetscFunctionReturn(0);
2082 }
2083 
2084 /* -------------------------------------------------------------------------*/
2085 PetscErrorCode MatGetSubMatrices_MPIAIJ_Local(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,PetscBool *allcolumns,Mat *submats)
2086 {
2087   Mat_MPIAIJ     *c = (Mat_MPIAIJ*)C->data;
2088   Mat            A  = c->A;
2089   Mat_SeqAIJ     *a = (Mat_SeqAIJ*)A->data,*b = (Mat_SeqAIJ*)c->B->data,*subc;
2090   const PetscInt **icol,**irow;
2091   PetscInt       *nrow,*ncol,start;
2092   PetscErrorCode ierr;
2093   PetscMPIInt    rank,size,tag0,tag2,tag3,tag4,*w1,*w2,*w3,*w4,nrqr;
2094   PetscInt       **sbuf1,**sbuf2,i,j,k,l,ct1,ct2,**rbuf1,row,proc;
2095   PetscInt       nrqs,msz,**ptr,*req_size,*ctr,*pa,*tmp,tcol;
2096   PetscInt       **rbuf3,*req_source1,*req_source2,**sbuf_aj,**rbuf2,max1,max2;
2097   PetscInt       **lens,is_no,ncols,*cols,mat_i,*mat_j,tmp2,jmax;
2098 #if defined(PETSC_USE_CTABLE)
2099   PetscTable     *cmap,cmap_i=NULL,*rmap,rmap_i;
2100 #else
2101   PetscInt       **cmap,*cmap_i=NULL,**rmap,*rmap_i;
2102 #endif
2103   const PetscInt *irow_i;
2104   PetscInt       ctr_j,*sbuf1_j,*sbuf_aj_i,*rbuf1_i,kmax,*lens_i;
2105   MPI_Request    *s_waits1,*r_waits1,*s_waits2,*r_waits2,*r_waits3;
2106   MPI_Request    *r_waits4,*s_waits3,*s_waits4;
2107   MPI_Status     *r_status1,*r_status2,*s_status1,*s_status3,*s_status2;
2108   MPI_Status     *r_status3,*r_status4,*s_status4;
2109   MPI_Comm       comm;
2110   PetscScalar    **rbuf4,**sbuf_aa,*vals,*mat_a,*sbuf_aa_i;
2111   PetscMPIInt    *onodes1,*olengths1,end;
2112   PetscInt       **row2proc,*row2proc_i;
2113   Mat_SubMat     **smats,*smat_i;
2114   PetscBool      *issorted;
2115 
2116   PetscFunctionBegin;
2117   ierr = PetscObjectGetComm((PetscObject)C,&comm);CHKERRQ(ierr);
2118   size = c->size;
2119   rank = c->rank;
2120 
2121   ierr = PetscMalloc5(ismax,&irow,ismax,&icol,ismax,&nrow,ismax,&ncol,ismax,&issorted);CHKERRQ(ierr);
2122   for (i=0; i<ismax; i++) {
2123     ierr = ISSorted(isrow[i],&issorted[i]);CHKERRQ(ierr);
2124 
2125     ierr = ISGetIndices(isrow[i],&irow[i]);CHKERRQ(ierr);
2126     ierr = ISGetLocalSize(isrow[i],&nrow[i]);CHKERRQ(ierr);
2127     if (allcolumns[i]) {
2128       icol[i] = NULL;
2129       ncol[i] = C->cmap->N;
2130     } else {
2131       ierr = ISGetIndices(iscol[i],&icol[i]);CHKERRQ(ierr);
2132       ierr = ISGetLocalSize(iscol[i],&ncol[i]);CHKERRQ(ierr);
2133     }
2134   }
2135 
2136   ierr = PetscMalloc1(ismax,&smats);CHKERRQ(ierr);
2137   ierr = PetscMalloc1(ismax,&row2proc);CHKERRQ(ierr);
2138   ierr = PetscMalloc2(ismax,&cmap,ismax,&rmap);CHKERRQ(ierr);
2139 
2140   if (scall == MAT_REUSE_MATRIX) {
2141     /* Assumes new rows are same length as the old rows */
2142     for (i=0; i<ismax; i++) {
2143       subc = (Mat_SeqAIJ*)(submats[i]->data);
2144       if ((submats[i]->rmap->n != nrow[i]) || (submats[i]->cmap->n != ncol[i])) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Cannot reuse matrix. wrong size");
2145 
2146       /* Initial matrix as if empty */
2147       ierr = PetscMemzero(subc->ilen,submats[i]->rmap->n*sizeof(PetscInt));CHKERRQ(ierr);
2148 
2149       /* Initial matrix as if empty */
2150       submats[i]->factortype = C->factortype;
2151 
2152       smat_i   = subc->submatis1;
2153       smats[i] = smat_i;
2154 
2155       nrqs        = smat_i->nrqs;
2156       nrqr        = smat_i->nrqr;
2157       rbuf1       = smat_i->rbuf1;
2158       rbuf2       = smat_i->rbuf2;
2159       rbuf3       = smat_i->rbuf3;
2160       req_source2 = smat_i->req_source2;
2161 
2162       sbuf1     = smat_i->sbuf1;
2163       sbuf2     = smat_i->sbuf2;
2164       ptr       = smat_i->ptr;
2165       tmp       = smat_i->tmp;
2166       ctr       = smat_i->ctr;
2167 
2168       pa          = smat_i->pa;
2169       req_size    = smat_i->req_size;
2170       req_source1 = smat_i->req_source1;
2171 
2172       allcolumns[i] = smat_i->allcolumns;
2173       row2proc[i]   = smat_i->row2proc;
2174       rmap[i]       = smat_i->rmap;
2175       cmap[i]       = smat_i->cmap;
2176     }
2177   } else { /* scall == MAT_INITIAL_MATRIX */
2178     /* Get some new tags to keep the communication clean */
2179     ierr = PetscObjectGetNewTag((PetscObject)C,&tag2);CHKERRQ(ierr);
2180     ierr = PetscObjectGetNewTag((PetscObject)C,&tag3);CHKERRQ(ierr);
2181 
2182     /* evaluate communication - mesg to who, length of mesg, and buffer space
2183      required. Based on this, buffers are allocated, and data copied into them*/
2184     ierr = PetscCalloc4(size,&w1,size,&w2,size,&w3,size,&w4);CHKERRQ(ierr);   /* mesg size, initialize work vectors */
2185 
2186     for (i=0; i<ismax; i++) {
2187       jmax   = nrow[i];
2188       irow_i = irow[i];
2189 
2190       ierr   = PetscMalloc1(jmax,&row2proc_i);CHKERRQ(ierr);
2191       row2proc[i] = row2proc_i;
2192 
2193       if (issorted[i]) proc = 0;
2194       for (j=0; j<jmax; j++) {
2195         if (!issorted[i]) proc = 0;
2196         row = irow_i[j];
2197         while (row >= C->rmap->range[proc+1]) proc++;
2198         w4[proc]++;
2199         row2proc_i[j] = proc; /* map row index to proc */
2200       }
2201       for (j=0; j<size; j++) {
2202         if (w4[j]) { w1[j] += w4[j];  w3[j]++; w4[j] = 0;}
2203       }
2204     }
2205 
2206     nrqs     = 0;              /* no of outgoing messages */
2207     msz      = 0;              /* total mesg length (for all procs) */
2208     w1[rank] = 0;              /* no mesg sent to self */
2209     w3[rank] = 0;
2210     for (i=0; i<size; i++) {
2211       if (w1[i])  { w2[i] = 1; nrqs++;} /* there exists a message to proc i */
2212     }
2213     ierr = PetscMalloc1(nrqs+1,&pa);CHKERRQ(ierr); /*(proc -array)*/
2214     for (i=0,j=0; i<size; i++) {
2215       if (w1[i]) { pa[j] = i; j++; }
2216     }
2217 
2218     /* Each message would have a header = 1 + 2*(no of IS) + data */
2219     for (i=0; i<nrqs; i++) {
2220       j      = pa[i];
2221       w1[j] += w2[j] + 2* w3[j];
2222       msz   += w1[j];
2223     }
2224     ierr = PetscInfo2(0,"Number of outgoing messages %D Total message length %D\n",nrqs,msz);CHKERRQ(ierr);
2225 
2226     /* Determine the number of messages to expect, their lengths, from from-ids */
2227     ierr = PetscGatherNumberOfMessages(comm,w2,w1,&nrqr);CHKERRQ(ierr);
2228     ierr = PetscGatherMessageLengths(comm,nrqs,nrqr,w1,&onodes1,&olengths1);CHKERRQ(ierr);
2229 
2230     /* Now post the Irecvs corresponding to these messages */
2231     tag0 = ((PetscObject)C)->tag;
2232     ierr = PetscPostIrecvInt(comm,tag0,nrqr,onodes1,olengths1,&rbuf1,&r_waits1);CHKERRQ(ierr);
2233 
2234     ierr = PetscFree(onodes1);CHKERRQ(ierr);
2235     ierr = PetscFree(olengths1);CHKERRQ(ierr);
2236 
2237     /* Allocate Memory for outgoing messages */
2238     ierr = PetscMalloc4(size,&sbuf1,size,&ptr,2*msz,&tmp,size,&ctr);CHKERRQ(ierr);
2239     ierr = PetscMemzero(sbuf1,size*sizeof(PetscInt*));CHKERRQ(ierr);
2240     ierr = PetscMemzero(ptr,size*sizeof(PetscInt*));CHKERRQ(ierr);
2241 
2242     {
2243       PetscInt *iptr = tmp;
2244       k    = 0;
2245       for (i=0; i<nrqs; i++) {
2246         j        = pa[i];
2247         iptr    += k;
2248         sbuf1[j] = iptr;
2249         k        = w1[j];
2250       }
2251     }
2252 
2253     /* Form the outgoing messages. Initialize the header space */
2254     for (i=0; i<nrqs; i++) {
2255       j           = pa[i];
2256       sbuf1[j][0] = 0;
2257       ierr        = PetscMemzero(sbuf1[j]+1,2*w3[j]*sizeof(PetscInt));CHKERRQ(ierr);
2258       ptr[j]      = sbuf1[j] + 2*w3[j] + 1;
2259     }
2260 
2261     /* Parse the isrow and copy data into outbuf */
2262     for (i=0; i<ismax; i++) {
2263       row2proc_i = row2proc[i];
2264       ierr   = PetscMemzero(ctr,size*sizeof(PetscInt));CHKERRQ(ierr);
2265       irow_i = irow[i];
2266       jmax   = nrow[i];
2267       for (j=0; j<jmax; j++) {  /* parse the indices of each IS */
2268         proc = row2proc_i[j];
2269         if (proc != rank) { /* copy to the outgoing buf*/
2270           ctr[proc]++;
2271           *ptr[proc] = irow_i[j];
2272           ptr[proc]++;
2273         }
2274       }
2275       /* Update the headers for the current IS */
2276       for (j=0; j<size; j++) { /* Can Optimise this loop too */
2277         if ((ctr_j = ctr[j])) {
2278           sbuf1_j        = sbuf1[j];
2279           k              = ++sbuf1_j[0];
2280           sbuf1_j[2*k]   = ctr_j;
2281           sbuf1_j[2*k-1] = i;
2282         }
2283       }
2284     }
2285 
2286     /*  Now  post the sends */
2287     ierr = PetscMalloc1(nrqs+1,&s_waits1);CHKERRQ(ierr);
2288     for (i=0; i<nrqs; ++i) {
2289       j    = pa[i];
2290       ierr = MPI_Isend(sbuf1[j],w1[j],MPIU_INT,j,tag0,comm,s_waits1+i);CHKERRQ(ierr);
2291     }
2292 
2293     /* Post Receives to capture the buffer size */
2294     ierr = PetscMalloc1(nrqs+1,&r_waits2);CHKERRQ(ierr);
2295     ierr = PetscMalloc3(nrqs+1,&req_source2,nrqs+1,&rbuf2,nrqs+1,&rbuf3);CHKERRQ(ierr);
2296     rbuf2[0] = tmp + msz;
2297     for (i=1; i<nrqs; ++i) {
2298       rbuf2[i] = rbuf2[i-1]+w1[pa[i-1]];
2299     }
2300     for (i=0; i<nrqs; ++i) {
2301       j    = pa[i];
2302       ierr = MPI_Irecv(rbuf2[i],w1[j],MPIU_INT,j,tag2,comm,r_waits2+i);CHKERRQ(ierr);
2303     }
2304 
2305     /* Send to other procs the buf size they should allocate */
2306     /* Receive messages*/
2307     ierr = PetscMalloc1(nrqr+1,&s_waits2);CHKERRQ(ierr);
2308     ierr = PetscMalloc1(nrqr+1,&r_status1);CHKERRQ(ierr);
2309     ierr = PetscMalloc3(nrqr,&sbuf2,nrqr,&req_size,nrqr,&req_source1);CHKERRQ(ierr);
2310     {
2311       PetscInt   *sAi = a->i,*sBi = b->i,id,rstart = C->rmap->rstart;
2312       PetscInt   *sbuf2_i;
2313 
2314       ierr = MPI_Waitall(nrqr,r_waits1,r_status1);CHKERRQ(ierr);
2315       for (i=0; i<nrqr; ++i) {
2316         req_size[i] = 0;
2317         rbuf1_i        = rbuf1[i];
2318         start          = 2*rbuf1_i[0] + 1;
2319         ierr           = MPI_Get_count(r_status1+i,MPIU_INT,&end);CHKERRQ(ierr);
2320         ierr           = PetscMalloc1(end+1,&sbuf2[i]);CHKERRQ(ierr);
2321         sbuf2_i        = sbuf2[i];
2322         for (j=start; j<end; j++) {
2323           id              = rbuf1_i[j] - rstart;
2324           ncols           = sAi[id+1] - sAi[id] + sBi[id+1] - sBi[id];
2325           sbuf2_i[j]      = ncols;
2326           req_size[i] += ncols;
2327         }
2328         req_source1[i] = r_status1[i].MPI_SOURCE;
2329         /* form the header */
2330         sbuf2_i[0] = req_size[i];
2331         for (j=1; j<start; j++) sbuf2_i[j] = rbuf1_i[j];
2332 
2333         ierr = MPI_Isend(sbuf2_i,end,MPIU_INT,req_source1[i],tag2,comm,s_waits2+i);CHKERRQ(ierr);
2334       }
2335     }
2336     ierr = PetscFree(r_status1);CHKERRQ(ierr);
2337     ierr = PetscFree(r_waits1);CHKERRQ(ierr);
2338     ierr = PetscFree4(w1,w2,w3,w4);CHKERRQ(ierr);
2339 
2340     /* Receive messages*/
2341     ierr = PetscMalloc1(nrqs+1,&r_waits3);CHKERRQ(ierr);
2342     ierr = PetscMalloc1(nrqs+1,&r_status2);CHKERRQ(ierr);
2343 
2344     ierr = MPI_Waitall(nrqs,r_waits2,r_status2);CHKERRQ(ierr);
2345     for (i=0; i<nrqs; ++i) {
2346       ierr = PetscMalloc1(rbuf2[i][0]+1,&rbuf3[i]);CHKERRQ(ierr);
2347       req_source2[i] = r_status2[i].MPI_SOURCE;
2348       ierr = MPI_Irecv(rbuf3[i],rbuf2[i][0],MPIU_INT,req_source2[i],tag3,comm,r_waits3+i);CHKERRQ(ierr);
2349     }
2350     ierr = PetscFree(r_status2);CHKERRQ(ierr);
2351     ierr = PetscFree(r_waits2);CHKERRQ(ierr);
2352 
2353     /* Wait on sends1 and sends2 */
2354     ierr = PetscMalloc1(nrqs+1,&s_status1);CHKERRQ(ierr);
2355     ierr = PetscMalloc1(nrqr+1,&s_status2);CHKERRQ(ierr);
2356 
2357     if (nrqs) {ierr = MPI_Waitall(nrqs,s_waits1,s_status1);CHKERRQ(ierr);}
2358     if (nrqr) {ierr = MPI_Waitall(nrqr,s_waits2,s_status2);CHKERRQ(ierr);}
2359     ierr = PetscFree(s_status1);CHKERRQ(ierr);
2360     ierr = PetscFree(s_status2);CHKERRQ(ierr);
2361     ierr = PetscFree(s_waits1);CHKERRQ(ierr);
2362     ierr = PetscFree(s_waits2);CHKERRQ(ierr);
2363 
2364     /* Now allocate sending buffers for a->j, and send them off */
2365     ierr = PetscMalloc1(nrqr+1,&sbuf_aj);CHKERRQ(ierr);
2366     for (i=0,j=0; i<nrqr; i++) j += req_size[i];
2367     ierr = PetscMalloc1(j+1,&sbuf_aj[0]);CHKERRQ(ierr);
2368     for (i=1; i<nrqr; i++) sbuf_aj[i] = sbuf_aj[i-1] + req_size[i-1];
2369 
2370     ierr = PetscMalloc1(nrqr+1,&s_waits3);CHKERRQ(ierr);
2371     {
2372       PetscInt nzA,nzB,*a_i = a->i,*b_i = b->i,lwrite;
2373       PetscInt *cworkA,*cworkB,cstart = C->cmap->rstart,rstart = C->rmap->rstart,*bmap = c->garray;
2374       PetscInt cend = C->cmap->rend;
2375       PetscInt *a_j = a->j,*b_j = b->j,ctmp;
2376 
2377       for (i=0; i<nrqr; i++) {
2378         rbuf1_i   = rbuf1[i];
2379         sbuf_aj_i = sbuf_aj[i];
2380         ct1       = 2*rbuf1_i[0] + 1;
2381         ct2       = 0;
2382         for (j=1,max1=rbuf1_i[0]; j<=max1; j++) {
2383           kmax = rbuf1[i][2*j];
2384           for (k=0; k<kmax; k++,ct1++) {
2385             row    = rbuf1_i[ct1] - rstart;
2386             nzA    = a_i[row+1] - a_i[row]; nzB = b_i[row+1] - b_i[row];
2387             ncols  = nzA + nzB;
2388             cworkA = a_j + a_i[row]; cworkB = b_j + b_i[row];
2389 
2390             /* load the column indices for this row into sorted cols */
2391             cols = sbuf_aj_i + ct2;
2392 
2393             lwrite = 0;
2394             for (l=0; l<nzB; l++) {
2395               if ((ctmp = bmap[cworkB[l]]) < cstart) cols[lwrite++] = ctmp;
2396             }
2397             for (l=0; l<nzA; l++) cols[lwrite++] = cstart + cworkA[l];
2398             for (l=0; l<nzB; l++) {
2399               if ((ctmp = bmap[cworkB[l]]) >= cend) cols[lwrite++] = ctmp;
2400             }
2401 
2402             ct2 += ncols;
2403           }
2404         }
2405         ierr = MPI_Isend(sbuf_aj_i,req_size[i],MPIU_INT,req_source1[i],tag3,comm,s_waits3+i);CHKERRQ(ierr);
2406       }
2407     }
2408     ierr = PetscMalloc1(nrqs+1,&r_status3);CHKERRQ(ierr);
2409     ierr = PetscMalloc1(nrqr+1,&s_status3);CHKERRQ(ierr);
2410 
2411     /* create col map: global col of C -> local col of submatrices */
2412     {
2413       const PetscInt *icol_i;
2414 #if defined(PETSC_USE_CTABLE)
2415       for (i=0; i<ismax; i++) {
2416         if (!allcolumns[i]) {
2417           ierr = PetscTableCreate(ncol[i]+1,C->cmap->N+1,&cmap[i]);CHKERRQ(ierr);
2418 
2419           jmax   = ncol[i];
2420           icol_i = icol[i];
2421           cmap_i = cmap[i];
2422           for (j=0; j<jmax; j++) {
2423             ierr = PetscTableAdd(cmap[i],icol_i[j]+1,j+1,INSERT_VALUES);CHKERRQ(ierr);
2424           }
2425         } else cmap[i] = NULL;
2426       }
2427 #else
2428       for (i=0; i<ismax; i++) {
2429         if (!allcolumns[i]) {
2430           ierr   = PetscMalloc1(C->cmap->N,&cmap[i]);CHKERRQ(ierr);
2431           ierr   = PetscMemzero(cmap[i],C->cmap->N*sizeof(PetscInt));CHKERRQ(ierr);
2432           jmax   = ncol[i];
2433           icol_i = icol[i];
2434           cmap_i = cmap[i];
2435           for (j=0; j<jmax; j++) {
2436             cmap_i[icol_i[j]] = j+1;
2437           }
2438         } else cmap[i] = NULL;
2439       }
2440 #endif
2441     }
2442 
2443     /* Create lens which is required for MatCreate... */
2444     for (i=0,j=0; i<ismax; i++) j += nrow[i];
2445     ierr = PetscMalloc1(ismax,&lens);CHKERRQ(ierr);
2446 
2447     if (ismax) {
2448       ierr = PetscCalloc1(j,&lens[0]);CHKERRQ(ierr);
2449     }
2450     for (i=1; i<ismax; i++) lens[i] = lens[i-1] + nrow[i-1];
2451 
2452     /* Update lens from local data */
2453     for (i=0; i<ismax; i++) {
2454       row2proc_i = row2proc[i];
2455       jmax = nrow[i];
2456       if (!allcolumns[i]) cmap_i = cmap[i];
2457       irow_i = irow[i];
2458       lens_i = lens[i];
2459       for (j=0; j<jmax; j++) {
2460         row = irow_i[j];
2461         proc = row2proc_i[j];
2462         if (proc == rank) {
2463           ierr = MatGetRow_MPIAIJ(C,row,&ncols,&cols,0);CHKERRQ(ierr);
2464           if (!allcolumns[i]) {
2465             for (k=0; k<ncols; k++) {
2466 #if defined(PETSC_USE_CTABLE)
2467               ierr = PetscTableFind(cmap_i,cols[k]+1,&tcol);CHKERRQ(ierr);
2468 #else
2469               tcol = cmap_i[cols[k]];
2470 #endif
2471               if (tcol) lens_i[j]++;
2472             }
2473           } else { /* allcolumns */
2474             lens_i[j] = ncols;
2475           }
2476           ierr = MatRestoreRow_MPIAIJ(C,row,&ncols,&cols,0);CHKERRQ(ierr);
2477         }
2478       }
2479     }
2480 
2481     /* Create row map: global row of C -> local row of submatrices */
2482 #if defined(PETSC_USE_CTABLE)
2483     for (i=0; i<ismax; i++) {
2484       ierr   = PetscTableCreate(nrow[i]+1,C->rmap->N+1,&rmap[i]);CHKERRQ(ierr);
2485       irow_i = irow[i];
2486       jmax   = nrow[i];
2487       for (j=0; j<jmax; j++) {
2488       ierr = PetscTableAdd(rmap[i],irow_i[j]+1,j+1,INSERT_VALUES);CHKERRQ(ierr);
2489       }
2490     }
2491 #else
2492     if (ismax) {
2493       ierr = PetscMalloc1(ismax*C->rmap->N,&rmap[0]);CHKERRQ(ierr);
2494       ierr = PetscMemzero(rmap[0],ismax*C->rmap->N*sizeof(PetscInt));CHKERRQ(ierr);
2495     }
2496     for (i=1; i<ismax; i++) rmap[i] = rmap[i-1] + C->rmap->N;
2497     for (i=0; i<ismax; i++) {
2498       rmap_i = rmap[i];
2499       irow_i = irow[i];
2500       jmax   = nrow[i];
2501       for (j=0; j<jmax; j++) {
2502         rmap_i[irow_i[j]] = j;
2503       }
2504     }
2505 #endif
2506 
2507     /* Update lens from offproc data */
2508     {
2509     PetscInt *rbuf2_i,*rbuf3_i,*sbuf1_i;
2510 
2511     ierr    = MPI_Waitall(nrqs,r_waits3,r_status3);CHKERRQ(ierr);
2512     for (tmp2=0; tmp2<nrqs; tmp2++) {
2513       sbuf1_i = sbuf1[pa[tmp2]];
2514       jmax    = sbuf1_i[0];
2515       ct1     = 2*jmax+1;
2516       ct2     = 0;
2517       rbuf2_i = rbuf2[tmp2];
2518       rbuf3_i = rbuf3[tmp2];
2519       for (j=1; j<=jmax; j++) {
2520         is_no  = sbuf1_i[2*j-1];
2521         max1   = sbuf1_i[2*j];
2522         lens_i = lens[is_no];
2523         if (!allcolumns[is_no]) cmap_i = cmap[is_no];
2524         rmap_i = rmap[is_no];
2525         for (k=0; k<max1; k++,ct1++) {
2526 #if defined(PETSC_USE_CTABLE)
2527           ierr = PetscTableFind(rmap_i,sbuf1_i[ct1]+1,&row);CHKERRQ(ierr);
2528           row--;
2529           if (row < 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"row not found in table");
2530 #else
2531           row = rmap_i[sbuf1_i[ct1]]; /* the val in the new matrix to be */
2532 #endif
2533           max2 = rbuf2_i[ct1];
2534           for (l=0; l<max2; l++,ct2++) {
2535             if (!allcolumns[is_no]) {
2536 #if defined(PETSC_USE_CTABLE)
2537               ierr = PetscTableFind(cmap_i,rbuf3_i[ct2]+1,&tcol);CHKERRQ(ierr);
2538 #else
2539               tcol = cmap_i[rbuf3_i[ct2]];
2540 #endif
2541               if (tcol) lens_i[row]++;
2542             } else { /* allcolumns */
2543               lens_i[row]++; /* lens_i[row] += max2 ? */
2544             }
2545           }
2546         }
2547       }
2548     }
2549     }
2550     ierr = PetscFree(r_status3);CHKERRQ(ierr);
2551     ierr = PetscFree(r_waits3);CHKERRQ(ierr);
2552     if (nrqr) {ierr = MPI_Waitall(nrqr,s_waits3,s_status3);CHKERRQ(ierr);}
2553     ierr = PetscFree(s_status3);CHKERRQ(ierr);
2554     ierr = PetscFree(s_waits3);CHKERRQ(ierr);
2555 
2556     /* Create the submatrices */
2557     for (i=0; i<ismax; i++) {
2558       PetscInt    rbs,cbs;
2559 
2560       ierr = ISGetBlockSize(isrow[i],&rbs);CHKERRQ(ierr);
2561       ierr = ISGetBlockSize(iscol[i],&cbs);CHKERRQ(ierr);
2562 
2563       ierr = MatCreate(PETSC_COMM_SELF,submats+i);CHKERRQ(ierr);
2564       ierr = MatSetSizes(submats[i],nrow[i],ncol[i],PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
2565 
2566       ierr = MatSetBlockSizes(submats[i],rbs,cbs);CHKERRQ(ierr);
2567       ierr = MatSetType(submats[i],((PetscObject)A)->type_name);CHKERRQ(ierr);
2568       ierr = MatSeqAIJSetPreallocation(submats[i],0,lens[i]);CHKERRQ(ierr);
2569 
2570       /* create struct Mat_SubMat and attached it to submat */
2571       ierr = PetscNew(&smat_i);CHKERRQ(ierr);
2572       subc = (Mat_SeqAIJ*)submats[i]->data;
2573       subc->submatis1 = smat_i;
2574       smats[i]        = smat_i;
2575 
2576       smat_i->destroy          = submats[i]->ops->destroy;
2577       submats[i]->ops->destroy = MatDestroy_MPIAIJ_MatGetSubmatrices;
2578       submats[i]->factortype   = C->factortype;
2579 
2580       smat_i->id          = i;
2581       smat_i->nrqs        = nrqs;
2582       smat_i->nrqr        = nrqr;
2583       smat_i->rbuf1       = rbuf1;
2584       smat_i->rbuf2       = rbuf2;
2585       smat_i->rbuf3       = rbuf3;
2586       smat_i->sbuf2       = sbuf2;
2587       smat_i->req_source2 = req_source2;
2588 
2589       smat_i->sbuf1       = sbuf1;
2590       smat_i->ptr         = ptr;
2591       smat_i->tmp         = tmp;
2592       smat_i->ctr         = ctr;
2593 
2594       smat_i->pa           = pa;
2595       smat_i->req_size     = req_size;
2596       smat_i->req_source1  = req_source1;
2597 
2598       smat_i->allcolumns  = allcolumns[i];
2599       smat_i->row2proc    = row2proc[i];
2600       smat_i->rmap        = rmap[i];
2601       smat_i->cmap        = cmap[i];
2602     }
2603 
2604     if (ismax) {ierr = PetscFree(lens[0]);CHKERRQ(ierr);}
2605     ierr = PetscFree(lens);CHKERRQ(ierr);
2606     ierr = PetscFree(sbuf_aj[0]);CHKERRQ(ierr);
2607     ierr = PetscFree(sbuf_aj);CHKERRQ(ierr);
2608 
2609   } /* endof scall == MAT_INITIAL_MATRIX */
2610 
2611   /* Post recv matrix values */
2612   ierr = PetscObjectGetNewTag((PetscObject)C,&tag4);CHKERRQ(ierr);
2613   ierr = PetscMalloc1(nrqs+1,&rbuf4);CHKERRQ(ierr);
2614   ierr = PetscMalloc1(nrqs+1,&r_waits4);CHKERRQ(ierr);
2615   ierr = PetscMalloc1(nrqs+1,&r_status4);CHKERRQ(ierr);
2616   ierr = PetscMalloc1(nrqr+1,&s_status4);CHKERRQ(ierr);
2617   for (i=0; i<nrqs; ++i) {
2618     ierr = PetscMalloc1(rbuf2[i][0]+1,&rbuf4[i]);CHKERRQ(ierr);
2619     ierr = MPI_Irecv(rbuf4[i],rbuf2[i][0],MPIU_SCALAR,req_source2[i],tag4,comm,r_waits4+i);CHKERRQ(ierr);
2620   }
2621 
2622   /* Allocate sending buffers for a->a, and send them off */
2623   ierr = PetscMalloc1(nrqr+1,&sbuf_aa);CHKERRQ(ierr);
2624   for (i=0,j=0; i<nrqr; i++) j += req_size[i];
2625   ierr = PetscMalloc1(j+1,&sbuf_aa[0]);CHKERRQ(ierr);
2626   for (i=1; i<nrqr; i++) sbuf_aa[i] = sbuf_aa[i-1] + req_size[i-1];
2627 
2628   ierr = PetscMalloc1(nrqr+1,&s_waits4);CHKERRQ(ierr);
2629   {
2630     PetscInt    nzA,nzB,*a_i = a->i,*b_i = b->i, *cworkB,lwrite;
2631     PetscInt    cstart = C->cmap->rstart,rstart = C->rmap->rstart,*bmap = c->garray;
2632     PetscInt    cend   = C->cmap->rend;
2633     PetscInt    *b_j   = b->j;
2634     PetscScalar *vworkA,*vworkB,*a_a = a->a,*b_a = b->a;
2635 
2636     for (i=0; i<nrqr; i++) {
2637       rbuf1_i   = rbuf1[i];
2638       sbuf_aa_i = sbuf_aa[i];
2639       ct1       = 2*rbuf1_i[0]+1;
2640       ct2       = 0;
2641       for (j=1,max1=rbuf1_i[0]; j<=max1; j++) {
2642         kmax = rbuf1_i[2*j];
2643         for (k=0; k<kmax; k++,ct1++) {
2644           row    = rbuf1_i[ct1] - rstart;
2645           nzA    = a_i[row+1] - a_i[row];     nzB = b_i[row+1] - b_i[row];
2646           ncols  = nzA + nzB;
2647           cworkB = b_j + b_i[row];
2648           vworkA = a_a + a_i[row];
2649           vworkB = b_a + b_i[row];
2650 
2651           /* load the column values for this row into vals*/
2652           vals = sbuf_aa_i+ct2;
2653 
2654           lwrite = 0;
2655           for (l=0; l<nzB; l++) {
2656             if ((bmap[cworkB[l]]) < cstart) vals[lwrite++] = vworkB[l];
2657           }
2658           for (l=0; l<nzA; l++) vals[lwrite++] = vworkA[l];
2659           for (l=0; l<nzB; l++) {
2660             if ((bmap[cworkB[l]]) >= cend) vals[lwrite++] = vworkB[l];
2661           }
2662 
2663           ct2 += ncols;
2664         }
2665       }
2666       ierr = MPI_Isend(sbuf_aa_i,req_size[i],MPIU_SCALAR,req_source1[i],tag4,comm,s_waits4+i);CHKERRQ(ierr);
2667     }
2668   }
2669 
2670   if (!ismax) {
2671     ierr = PetscFree(rbuf1[0]);CHKERRQ(ierr);
2672     ierr = PetscFree(rbuf1);CHKERRQ(ierr);
2673   }
2674 
2675   /* Assemble the matrices */
2676   /* First assemble the local rows */
2677   {
2678     PetscInt    ilen_row,*imat_ilen,*imat_j,*imat_i,old_row;
2679     PetscScalar *imat_a;
2680 
2681     for (i=0; i<ismax; i++) {
2682       row2proc_i = row2proc[i];
2683       subc      = (Mat_SeqAIJ*)submats[i]->data;
2684       imat_ilen = subc->ilen;
2685       imat_j    = subc->j;
2686       imat_i    = subc->i;
2687       imat_a    = subc->a;
2688 
2689       if (!allcolumns[i]) cmap_i = cmap[i];
2690       rmap_i = rmap[i];
2691       irow_i = irow[i];
2692       jmax   = nrow[i];
2693       for (j=0; j<jmax; j++) {
2694         row  = irow_i[j];
2695         proc = row2proc_i[j];
2696         if (proc == rank) {
2697           old_row = row;
2698 #if defined(PETSC_USE_CTABLE)
2699           ierr = PetscTableFind(rmap_i,row+1,&row);CHKERRQ(ierr);
2700           row--;
2701 #else
2702           row = rmap_i[row];
2703 #endif
2704           ilen_row = imat_ilen[row];
2705           ierr     = MatGetRow_MPIAIJ(C,old_row,&ncols,&cols,&vals);CHKERRQ(ierr);
2706           mat_i    = imat_i[row];
2707           mat_a    = imat_a + mat_i;
2708           mat_j    = imat_j + mat_i;
2709           if (!allcolumns[i]) {
2710             for (k=0; k<ncols; k++) {
2711 #if defined(PETSC_USE_CTABLE)
2712               ierr = PetscTableFind(cmap_i,cols[k]+1,&tcol);CHKERRQ(ierr);
2713 #else
2714               tcol = cmap_i[cols[k]];
2715 #endif
2716               if (tcol) {
2717                 *mat_j++ = tcol - 1;
2718                 *mat_a++ = vals[k];
2719                 ilen_row++;
2720               }
2721             }
2722           } else { /* allcolumns */
2723             for (k=0; k<ncols; k++) {
2724               *mat_j++ = cols[k];  /* global col index! */
2725               *mat_a++ = vals[k];
2726               ilen_row++;
2727             }
2728           }
2729           ierr = MatRestoreRow_MPIAIJ(C,old_row,&ncols,&cols,&vals);CHKERRQ(ierr);
2730 
2731           imat_ilen[row] = ilen_row;
2732         }
2733       }
2734     }
2735   }
2736 
2737   /*   Now assemble the off proc rows*/
2738   {
2739     PetscInt    *sbuf1_i,*rbuf2_i,*rbuf3_i,*imat_ilen,ilen;
2740     PetscInt    *imat_j,*imat_i;
2741     PetscScalar *imat_a,*rbuf4_i;
2742 
2743     ierr    = MPI_Waitall(nrqs,r_waits4,r_status4);CHKERRQ(ierr);
2744     for (tmp2=0; tmp2<nrqs; tmp2++) {
2745       sbuf1_i = sbuf1[pa[tmp2]];
2746       jmax    = sbuf1_i[0];
2747       ct1     = 2*jmax + 1;
2748       ct2     = 0;
2749       rbuf2_i = rbuf2[tmp2];
2750       rbuf3_i = rbuf3[tmp2];
2751       rbuf4_i = rbuf4[tmp2];
2752       for (j=1; j<=jmax; j++) {
2753         is_no     = sbuf1_i[2*j-1];
2754         rmap_i    = rmap[is_no];
2755         if (!allcolumns[is_no]) cmap_i = cmap[is_no];
2756         subc      = (Mat_SeqAIJ*)submats[is_no]->data;
2757         imat_ilen = subc->ilen;
2758         imat_j    = subc->j;
2759         imat_i    = subc->i;
2760         imat_a    = subc->a;
2761         max1      = sbuf1_i[2*j];
2762         for (k=0; k<max1; k++,ct1++) {
2763           row = sbuf1_i[ct1];
2764 #if defined(PETSC_USE_CTABLE)
2765           ierr = PetscTableFind(rmap_i,row+1,&row);CHKERRQ(ierr);
2766           row--;
2767 #else
2768           row = rmap_i[row];
2769 #endif
2770           ilen  = imat_ilen[row];
2771           mat_i = imat_i[row];
2772           mat_a = imat_a + mat_i;
2773           mat_j = imat_j + mat_i;
2774           max2  = rbuf2_i[ct1];
2775           if (!allcolumns[is_no]) {
2776             for (l=0; l<max2; l++,ct2++) {
2777 
2778 #if defined(PETSC_USE_CTABLE)
2779               ierr = PetscTableFind(cmap_i,rbuf3_i[ct2]+1,&tcol);CHKERRQ(ierr);
2780 #else
2781               tcol = cmap_i[rbuf3_i[ct2]];
2782 #endif
2783               if (tcol) {
2784                 *mat_j++ = tcol - 1;
2785                 *mat_a++ = rbuf4_i[ct2];
2786                 ilen++;
2787               }
2788             }
2789           } else { /* allcolumns */
2790             for (l=0; l<max2; l++,ct2++) {
2791               *mat_j++ = rbuf3_i[ct2]; /* same global column index of C */
2792               *mat_a++ = rbuf4_i[ct2];
2793               ilen++;
2794             }
2795           }
2796           imat_ilen[row] = ilen;
2797         }
2798       }
2799     }
2800   }
2801 
2802   ierr = PetscFree(r_status4);CHKERRQ(ierr);
2803   ierr = PetscFree(r_waits4);CHKERRQ(ierr);
2804   if (nrqr) {ierr = MPI_Waitall(nrqr,s_waits4,s_status4);CHKERRQ(ierr);}
2805   ierr = PetscFree(s_waits4);CHKERRQ(ierr);
2806   ierr = PetscFree(s_status4);CHKERRQ(ierr);
2807 
2808   /* Restore the indices */
2809   for (i=0; i<ismax; i++) {
2810     ierr = ISRestoreIndices(isrow[i],irow+i);CHKERRQ(ierr);
2811     if (!allcolumns[i]) {
2812       ierr = ISRestoreIndices(iscol[i],icol+i);CHKERRQ(ierr);
2813     }
2814   }
2815 
2816   for (i=0; i<ismax; i++) {
2817     ierr = MatAssemblyBegin(submats[i],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2818     ierr = MatAssemblyEnd(submats[i],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2819   }
2820 
2821   /* Destroy allocated memory */
2822   if (!ismax) {
2823     ierr = PetscFree(pa);CHKERRQ(ierr);
2824 
2825     ierr = PetscFree4(sbuf1,ptr,tmp,ctr);CHKERRQ(ierr);
2826     for (i=0; i<nrqr; ++i) {
2827       ierr = PetscFree(sbuf2[i]);CHKERRQ(ierr);
2828     }
2829     for (i=0; i<nrqs; ++i) {
2830       ierr = PetscFree(rbuf3[i]);CHKERRQ(ierr);
2831     }
2832 
2833     ierr = PetscFree3(sbuf2,req_size,req_source1);CHKERRQ(ierr);
2834     ierr = PetscFree3(req_source2,rbuf2,rbuf3);CHKERRQ(ierr);
2835   }
2836 
2837   ierr = PetscFree(sbuf_aa[0]);CHKERRQ(ierr);
2838   ierr = PetscFree(sbuf_aa);CHKERRQ(ierr);
2839   ierr = PetscFree5(irow,icol,nrow,ncol,issorted);CHKERRQ(ierr);
2840 
2841   for (i=0; i<nrqs; ++i) {
2842     ierr = PetscFree(rbuf4[i]);CHKERRQ(ierr);
2843   }
2844   ierr = PetscFree(rbuf4);CHKERRQ(ierr);
2845 
2846   ierr = PetscFree2(cmap,rmap);CHKERRQ(ierr);
2847   ierr = PetscFree(row2proc);CHKERRQ(ierr);
2848   ierr = PetscFree(smats);CHKERRQ(ierr);
2849   PetscFunctionReturn(0);
2850 }
2851 
2852 /*
2853  Permute A & B into C's *local* index space using rowemb,dcolemb for A and rowemb,ocolemb for B.
2854  Embeddings are supposed to be injections and the above implies that the range of rowemb is a subset
2855  of [0,m), dcolemb is in [0,n) and ocolemb is in [N-n).
2856  If pattern == DIFFERENT_NONZERO_PATTERN, C is preallocated according to A&B.
2857  After that B's columns are mapped into C's global column space, so that C is in the "disassembled"
2858  state, and needs to be "assembled" later by compressing B's column space.
2859 
2860  This function may be called in lieu of preallocation, so C should not be expected to be preallocated.
2861  Following this call, C->A & C->B have been created, even if empty.
2862  */
2863 PetscErrorCode MatSetSeqMats_MPIAIJ(Mat C,IS rowemb,IS dcolemb,IS ocolemb,MatStructure pattern,Mat A,Mat B)
2864 {
2865   /* If making this function public, change the error returned in this function away from _PLIB. */
2866   PetscErrorCode ierr;
2867   Mat_MPIAIJ     *aij;
2868   Mat_SeqAIJ     *Baij;
2869   PetscBool      seqaij,Bdisassembled;
2870   PetscInt       m,n,*nz,i,j,ngcol,col,rstart,rend,shift,count;
2871   PetscScalar    v;
2872   const PetscInt *rowindices,*colindices;
2873 
2874   PetscFunctionBegin;
2875   /* Check to make sure the component matrices (and embeddings) are compatible with C. */
2876   if (A) {
2877     ierr = PetscObjectTypeCompare((PetscObject)A,MATSEQAIJ,&seqaij);CHKERRQ(ierr);
2878     if (!seqaij) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Diagonal matrix is of wrong type");
2879     if (rowemb) {
2880       ierr = ISGetLocalSize(rowemb,&m);CHKERRQ(ierr);
2881       if (m != A->rmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Row IS of size %D is incompatible with diag matrix row size %D",m,A->rmap->n);
2882     } else {
2883       if (C->rmap->n != A->rmap->n) {
2884 	SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Diag seq matrix is row-incompatible with the MPIAIJ matrix");
2885       }
2886     }
2887     if (dcolemb) {
2888       ierr = ISGetLocalSize(dcolemb,&n);CHKERRQ(ierr);
2889       if (n != A->cmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Diag col IS of size %D is incompatible with diag matrix col size %D",n,A->cmap->n);
2890     } else {
2891       if (C->cmap->n != A->cmap->n) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Diag seq matrix is col-incompatible with the MPIAIJ matrix");
2892     }
2893   }
2894   if (B) {
2895     ierr = PetscObjectTypeCompare((PetscObject)B,MATSEQAIJ,&seqaij);CHKERRQ(ierr);
2896     if (!seqaij) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Off-diagonal matrix is of wrong type");
2897     if (rowemb) {
2898       ierr = ISGetLocalSize(rowemb,&m);CHKERRQ(ierr);
2899       if (m != B->rmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Row IS of size %D is incompatible with off-diag matrix row size %D",m,A->rmap->n);
2900     } else {
2901       if (C->rmap->n != B->rmap->n) {
2902 	SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Off-diag seq matrix is row-incompatible with the MPIAIJ matrix");
2903       }
2904     }
2905     if (ocolemb) {
2906       ierr = ISGetLocalSize(ocolemb,&n);CHKERRQ(ierr);
2907       if (n != B->cmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Off-diag col IS of size %D is incompatible with off-diag matrix col size %D",n,B->cmap->n);
2908     } else {
2909       if (C->cmap->N - C->cmap->n != B->cmap->n) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Off-diag seq matrix is col-incompatible with the MPIAIJ matrix");
2910     }
2911   }
2912 
2913   aij    = (Mat_MPIAIJ*)(C->data);
2914   if (!aij->A) {
2915     /* Mimic parts of MatMPIAIJSetPreallocation() */
2916     ierr   = MatCreate(PETSC_COMM_SELF,&aij->A);CHKERRQ(ierr);
2917     ierr   = MatSetSizes(aij->A,C->rmap->n,C->cmap->n,C->rmap->n,C->cmap->n);CHKERRQ(ierr);
2918     ierr   = MatSetBlockSizesFromMats(aij->A,C,C);CHKERRQ(ierr);
2919     ierr   = MatSetType(aij->A,MATSEQAIJ);CHKERRQ(ierr);
2920     ierr   = PetscLogObjectParent((PetscObject)C,(PetscObject)aij->A);CHKERRQ(ierr);
2921   }
2922   if (A) {
2923     ierr   = MatSetSeqMat_SeqAIJ(aij->A,rowemb,dcolemb,pattern,A);CHKERRQ(ierr);
2924   } else {
2925     ierr = MatSetUp(aij->A);CHKERRQ(ierr);
2926   }
2927   if (B) { /* Destroy the old matrix or the column map, depending on the sparsity pattern. */
2928     /*
2929       If pattern == DIFFERENT_NONZERO_PATTERN, we reallocate B and
2930       need to "disassemble" B -- convert it to using C's global indices.
2931       To insert the values we take the safer, albeit more expensive, route of MatSetValues().
2932 
2933       If pattern == SUBSET_NONZERO_PATTERN, we do not "disassemble" B and do not reallocate;
2934       we MatZeroValues(B) first, so there may be a bunch of zeros that, perhaps, could be compacted out.
2935 
2936       TODO: Put B's values into aij->B's aij structure in place using the embedding ISs?
2937       At least avoid calling MatSetValues() and the implied searches?
2938     */
2939 
2940     if (B && pattern == DIFFERENT_NONZERO_PATTERN) {
2941 #if defined(PETSC_USE_CTABLE)
2942       ierr = PetscTableDestroy(&aij->colmap);CHKERRQ(ierr);
2943 #else
2944       ierr = PetscFree(aij->colmap);CHKERRQ(ierr);
2945       /* A bit of a HACK: ideally we should deal with case aij->B all in one code block below. */
2946       if (aij->B) {
2947         ierr = PetscLogObjectMemory((PetscObject)C,-aij->B->cmap->n*sizeof(PetscInt));CHKERRQ(ierr);
2948       }
2949 #endif
2950       ngcol = 0;
2951       if (aij->lvec) {
2952 	ierr = VecGetSize(aij->lvec,&ngcol);CHKERRQ(ierr);
2953       }
2954       if (aij->garray) {
2955 	ierr = PetscFree(aij->garray);CHKERRQ(ierr);
2956 	ierr = PetscLogObjectMemory((PetscObject)C,-ngcol*sizeof(PetscInt));CHKERRQ(ierr);
2957       }
2958       ierr = VecDestroy(&aij->lvec);CHKERRQ(ierr);
2959       ierr = VecScatterDestroy(&aij->Mvctx);CHKERRQ(ierr);
2960     }
2961     if (aij->B && B && pattern == DIFFERENT_NONZERO_PATTERN) {
2962       ierr = MatDestroy(&aij->B);CHKERRQ(ierr);
2963     }
2964     if (aij->B && B && pattern == SUBSET_NONZERO_PATTERN) {
2965       ierr = MatZeroEntries(aij->B);CHKERRQ(ierr);
2966     }
2967   }
2968   Bdisassembled = PETSC_FALSE;
2969   if (!aij->B) {
2970     ierr = MatCreate(PETSC_COMM_SELF,&aij->B);CHKERRQ(ierr);
2971     ierr = PetscLogObjectParent((PetscObject)C,(PetscObject)aij->B);CHKERRQ(ierr);
2972     ierr = MatSetSizes(aij->B,C->rmap->n,C->cmap->N,C->rmap->n,C->cmap->N);CHKERRQ(ierr);
2973     ierr = MatSetBlockSizesFromMats(aij->B,B,B);CHKERRQ(ierr);
2974     ierr = MatSetType(aij->B,MATSEQAIJ);CHKERRQ(ierr);
2975     Bdisassembled = PETSC_TRUE;
2976   }
2977   if (B) {
2978     Baij = (Mat_SeqAIJ*)(B->data);
2979     if (pattern == DIFFERENT_NONZERO_PATTERN) {
2980       ierr = PetscMalloc1(B->rmap->n,&nz);CHKERRQ(ierr);
2981       for (i=0; i<B->rmap->n; i++) {
2982 	nz[i] = Baij->i[i+1] - Baij->i[i];
2983       }
2984       ierr = MatSeqAIJSetPreallocation(aij->B,0,nz);CHKERRQ(ierr);
2985       ierr = PetscFree(nz);CHKERRQ(ierr);
2986     }
2987 
2988     ierr  = PetscLayoutGetRange(C->rmap,&rstart,&rend);CHKERRQ(ierr);
2989     shift = rend-rstart;
2990     count = 0;
2991     rowindices = NULL;
2992     colindices = NULL;
2993     if (rowemb) {
2994       ierr = ISGetIndices(rowemb,&rowindices);CHKERRQ(ierr);
2995     }
2996     if (ocolemb) {
2997       ierr = ISGetIndices(ocolemb,&colindices);CHKERRQ(ierr);
2998     }
2999     for (i=0; i<B->rmap->n; i++) {
3000       PetscInt row;
3001       row = i;
3002       if (rowindices) row = rowindices[i];
3003       for (j=Baij->i[i]; j<Baij->i[i+1]; j++) {
3004 	col  = Baij->j[count];
3005 	if (colindices) col = colindices[col];
3006 	if (Bdisassembled && col>=rstart) col += shift;
3007 	v    = Baij->a[count];
3008 	ierr = MatSetValues(aij->B,1,&row,1,&col,&v,INSERT_VALUES);CHKERRQ(ierr);
3009 	++count;
3010       }
3011     }
3012     /* No assembly for aij->B is necessary. */
3013     /* FIXME: set aij->B's nonzerostate correctly. */
3014   } else {
3015     ierr = MatSetUp(aij->B);CHKERRQ(ierr);
3016   }
3017   C->preallocated  = PETSC_TRUE;
3018   C->was_assembled = PETSC_FALSE;
3019   C->assembled     = PETSC_FALSE;
3020    /*
3021       C will need to be assembled so that aij->B can be compressed into local form in MatSetUpMultiply_MPIAIJ().
3022       Furthermore, its nonzerostate will need to be based on that of aij->A's and aij->B's.
3023    */
3024   PetscFunctionReturn(0);
3025 }
3026 
3027 /*
3028   B uses local indices with column indices ranging between 0 and N-n; they  must be interpreted using garray.
3029  */
3030 PetscErrorCode MatGetSeqMats_MPIAIJ(Mat C,Mat *A,Mat *B)
3031 {
3032   Mat_MPIAIJ *aij = (Mat_MPIAIJ*) (C->data);
3033 
3034   PetscFunctionBegin;
3035   PetscValidPointer(A,2);
3036   PetscValidPointer(B,3);
3037   /* FIXME: make sure C is assembled */
3038   *A = aij->A;
3039   *B = aij->B;
3040   /* Note that we don't incref *A and *B, so be careful! */
3041   PetscFunctionReturn(0);
3042 }
3043 
3044 /*
3045   Extract MPI submatrices encoded by pairs of IS that may live on subcomms of C.
3046   NOT SCALABLE due to the use of ISGetNonlocalIS() (see below).
3047 */
3048 PetscErrorCode MatGetSubMatricesMPI_MPIXAIJ(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,Mat *submat[],
3049                                                  PetscErrorCode(*getsubmats_seq)(Mat,PetscInt,const IS[],const IS[],MatReuse,Mat**),
3050 					         PetscErrorCode(*getlocalmats)(Mat,Mat*,Mat*),
3051 					         PetscErrorCode(*setseqmat)(Mat,IS,IS,MatStructure,Mat),
3052 					         PetscErrorCode(*setseqmats)(Mat,IS,IS,IS,MatStructure,Mat,Mat))
3053 {
3054   PetscErrorCode ierr;
3055   PetscMPIInt    isize,flag;
3056   PetscInt       i,ii,cismax,ispar;
3057   Mat            *A,*B;
3058   IS             *isrow_p,*iscol_p,*cisrow,*ciscol,*ciscol_p;
3059 
3060   PetscFunctionBegin;
3061   if (!ismax) PetscFunctionReturn(0);
3062 
3063   for (i = 0, cismax = 0; i < ismax; ++i) {
3064     PetscMPIInt isize;
3065     ierr = MPI_Comm_compare(((PetscObject)isrow[i])->comm,((PetscObject)iscol[i])->comm,&flag);CHKERRQ(ierr);
3066     if (flag != MPI_IDENT) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Row and column index sets must have the same communicator");
3067     ierr = MPI_Comm_size(((PetscObject)isrow[i])->comm, &isize);CHKERRQ(ierr);
3068     if (isize > 1) ++cismax;
3069   }
3070 
3071   /*
3072      If cismax is zero on all C's ranks, then and only then can we use purely sequential matrix extraction.
3073      ispar counts the number of parallel ISs across C's comm.
3074   */
3075   ierr = MPIU_Allreduce(&cismax,&ispar,1,MPIU_INT,MPI_MAX,PetscObjectComm((PetscObject)C));CHKERRQ(ierr);
3076   if (!ispar) { /* Sequential ISs only across C's comm, so can call the sequential matrix extraction subroutine. */
3077     ierr = (*getsubmats_seq)(C,ismax,isrow,iscol,scall,submat);CHKERRQ(ierr);
3078     PetscFunctionReturn(0);
3079   }
3080 
3081   /* if (ispar) */
3082   /*
3083     Construct the "complements" -- the off-processor indices -- of the iscol ISs for parallel ISs only.
3084     These are used to extract the off-diag portion of the resulting parallel matrix.
3085     The row IS for the off-diag portion is the same as for the diag portion,
3086     so we merely alias (without increfing) the row IS, while skipping those that are sequential.
3087   */
3088   ierr = PetscMalloc2(cismax,&cisrow,cismax,&ciscol);CHKERRQ(ierr);
3089   ierr = PetscMalloc1(cismax,&ciscol_p);CHKERRQ(ierr);
3090   for (i = 0, ii = 0; i < ismax; ++i) {
3091     ierr = MPI_Comm_size(((PetscObject)isrow[i])->comm,&isize);CHKERRQ(ierr);
3092     if (isize > 1) {
3093       /*
3094 	 TODO: This is the part that's ***NOT SCALABLE***.
3095 	 To fix this we need to extract just the indices of C's nonzero columns
3096 	 that lie on the intersection of isrow[i] and ciscol[ii] -- the nonlocal
3097 	 part of iscol[i] -- without actually computing ciscol[ii]. This also has
3098 	 to be done without serializing on the IS list, so, most likely, it is best
3099 	 done by rewriting MatGetSubMatrices_MPIAIJ() directly.
3100       */
3101       ierr = ISGetNonlocalIS(iscol[i],&(ciscol[ii]));CHKERRQ(ierr);
3102       /* Now we have to
3103 	 (a) make sure ciscol[ii] is sorted, since, even if the off-proc indices
3104 	     were sorted on each rank, concatenated they might no longer be sorted;
3105 	 (b) Use ISSortPermutation() to construct ciscol_p, the mapping from the
3106 	     indices in the nondecreasing order to the original index positions.
3107 	 If ciscol[ii] is strictly increasing, the permutation IS is NULL.
3108       */
3109       ierr = ISSortPermutation(ciscol[ii],PETSC_FALSE,ciscol_p+ii);CHKERRQ(ierr);
3110       ierr = ISSort(ciscol[ii]);CHKERRQ(ierr);
3111       ++ii;
3112     }
3113   }
3114   ierr = PetscMalloc2(ismax,&isrow_p,ismax,&iscol_p);CHKERRQ(ierr);
3115   for (i = 0, ii = 0; i < ismax; ++i) {
3116     PetscInt       j,issize;
3117     const PetscInt *indices;
3118 
3119     /*
3120        Permute the indices into a nondecreasing order. Reject row and col indices with duplicates.
3121      */
3122     ierr = ISSortPermutation(isrow[i],PETSC_FALSE,isrow_p+i);CHKERRQ(ierr);
3123     ierr = ISSort(isrow[i]);CHKERRQ(ierr);
3124     ierr = ISGetLocalSize(isrow[i],&issize);CHKERRQ(ierr);
3125     ierr = ISGetIndices(isrow[i],&indices);CHKERRQ(ierr);
3126     for (j = 1; j < issize; ++j) {
3127       if (indices[j] == indices[j-1]) {
3128 	SETERRQ4(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Repeated indices in row IS %D: indices at %D and %D are both %D",i,j-1,j,indices[j]);
3129       }
3130     }
3131     ierr = ISRestoreIndices(isrow[i],&indices);CHKERRQ(ierr);
3132 
3133 
3134     ierr = ISSortPermutation(iscol[i],PETSC_FALSE,iscol_p+i);CHKERRQ(ierr);
3135     ierr = ISSort(iscol[i]);CHKERRQ(ierr);
3136     ierr = ISGetLocalSize(iscol[i],&issize);CHKERRQ(ierr);
3137     ierr = ISGetIndices(iscol[i],&indices);CHKERRQ(ierr);
3138     for (j = 1; j < issize; ++j) {
3139       if (indices[j-1] == indices[j]) {
3140 	SETERRQ4(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Repeated indices in col IS %D: indices at %D and %D are both %D",i,j-1,j,indices[j]);
3141       }
3142     }
3143     ierr = ISRestoreIndices(iscol[i],&indices);CHKERRQ(ierr);
3144     ierr = MPI_Comm_size(((PetscObject)isrow[i])->comm,&isize);CHKERRQ(ierr);
3145     if (isize > 1) {
3146       cisrow[ii] = isrow[i];
3147       ++ii;
3148     }
3149   }
3150   /*
3151     Allocate the necessary arrays to hold the resulting parallel matrices as well as the intermediate
3152     array of sequential matrices underlying the resulting parallel matrices.
3153     Which arrays to allocate is based on the value of MatReuse scall and whether ISs are sorted and/or
3154     contain duplicates.
3155 
3156     There are as many diag matrices as there are original index sets. There are only as many parallel
3157     and off-diag matrices, as there are parallel (comm size > 1) index sets.
3158 
3159     ARRAYS that can hold Seq matrices get allocated in any event -- either here or by getsubmats_seq():
3160     - If the array of MPI matrices already exists and is being reused, we need to allocate the array
3161       and extract the underlying seq matrices into it to serve as placeholders, into which getsubmats_seq
3162       will deposite the extracted diag and off-diag parts. Thus, we allocate the A&B arrays and fill them
3163       with A[i] and B[ii] extracted from the corresponding MPI submat.
3164     - However, if the rows, A's column indices or B's column indices are not sorted, the extracted A[i] & B[ii]
3165       will have a different order from what getsubmats_seq expects.  To handle this case -- indicated
3166       by a nonzero isrow_p[i], iscol_p[i], or ciscol_p[ii] -- we duplicate A[i] --> AA[i], B[ii] --> BB[ii]
3167       (retrieve composed AA[i] or BB[ii]) and reuse them here. AA[i] and BB[ii] are then used to permute its
3168       values into A[i] and B[ii] sitting inside the corresponding submat.
3169     - If no reuse is taking place then getsubmats_seq will allocate the A&B arrays and create the corresponding
3170       A[i], B[ii], AA[i] or BB[ii] matrices.
3171   */
3172   /* Parallel matrix array is allocated here only if no reuse is taking place. If reused, it is passed in by the caller. */
3173   if (scall == MAT_INITIAL_MATRIX) {
3174     ierr = PetscMalloc1(ismax,submat);CHKERRQ(ierr);
3175   }
3176 
3177   /* Now obtain the sequential A and B submatrices separately. */
3178   /* scall=MAT_REUSE_MATRIX is not handled yet, because getsubmats_seq() requires reuse of A and B */
3179   ierr = (*getsubmats_seq)(C,ismax,isrow,iscol,MAT_INITIAL_MATRIX,&A);CHKERRQ(ierr);
3180   ierr = (*getsubmats_seq)(C,cismax,cisrow,ciscol,MAT_INITIAL_MATRIX,&B);CHKERRQ(ierr);
3181 
3182   /*
3183     If scall == MAT_REUSE_MATRIX AND the permutations are NULL, we are done, since the sequential
3184     matrices A & B have been extracted directly into the parallel matrices containing them, or
3185     simply into the sequential matrix identical with the corresponding A (if isize == 1).
3186     Note that in that case colmap doesn't need to be rebuilt, since the matrices are expected
3187     to have the same sparsity pattern.
3188     Otherwise, A and/or B have to be properly embedded into C's index spaces and the correct colmap
3189     must be constructed for C. This is done by setseqmat(s).
3190   */
3191   for (i = 0, ii = 0; i < ismax; ++i) {
3192     /*
3193        TODO: cache ciscol, permutation ISs and maybe cisrow? What about isrow & iscol?
3194        That way we can avoid sorting and computing permutations when reusing.
3195        To this end:
3196         - remove the old cache, if it exists, when extracting submatrices with MAT_INITIAL_MATRIX
3197 	- if caching arrays to hold the ISs, make and compose a container for them so that it can
3198 	  be destroyed upon destruction of C (use PetscContainerUserDestroy() to clear out the contents).
3199     */
3200     MatStructure pattern;
3201     pattern = DIFFERENT_NONZERO_PATTERN;
3202 
3203     ierr = MPI_Comm_size(((PetscObject)isrow[i])->comm,&isize);CHKERRQ(ierr);
3204     /* Construct submat[i] from the Seq pieces A (and B, if necessary). */
3205     if (isize > 1) {
3206       if (scall == MAT_INITIAL_MATRIX) {
3207 	ierr = MatCreate(((PetscObject)isrow[i])->comm,(*submat)+i);CHKERRQ(ierr);
3208 	ierr = MatSetSizes((*submat)[i],A[i]->rmap->n,A[i]->cmap->n,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
3209 	ierr = MatSetType((*submat)[i],MATMPIAIJ);CHKERRQ(ierr);
3210 	ierr = PetscLayoutSetUp((*submat)[i]->rmap);CHKERRQ(ierr);
3211 	ierr = PetscLayoutSetUp((*submat)[i]->cmap);CHKERRQ(ierr);
3212       }
3213       /*
3214 	For each parallel isrow[i], insert the extracted sequential matrices into the parallel matrix.
3215       */
3216       {
3217 	Mat AA,BB;
3218         AA = A[i];
3219         BB = B[ii];
3220 	if (AA || BB) {
3221 	  ierr = setseqmats((*submat)[i],isrow_p[i],iscol_p[i],ciscol_p[ii],pattern,AA,BB);CHKERRQ(ierr);
3222 	  ierr = MatAssemblyBegin((*submat)[i],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
3223 	  ierr = MatAssemblyEnd((*submat)[i],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
3224 	}
3225 
3226         ierr = MatDestroy(&AA);CHKERRQ(ierr);
3227         ierr = MatDestroy(&BB);CHKERRQ(ierr);
3228       }
3229       ierr = ISDestroy(ciscol+ii);CHKERRQ(ierr);
3230       ierr = ISDestroy(ciscol_p+ii);CHKERRQ(ierr);
3231       ++ii;
3232     } else { /* if (isize == 1) */
3233       if (scall == MAT_REUSE_MATRIX) {
3234         ierr = MatDestroy(&(*submat)[i]);CHKERRQ(ierr);
3235       }
3236       if (isrow_p[i] || iscol_p[i]) {
3237         ierr = MatDuplicate(A[i],MAT_DO_NOT_COPY_VALUES,(*submat)+i);CHKERRQ(ierr);
3238         ierr = setseqmat((*submat)[i],isrow_p[i],iscol_p[i],pattern,A[i]);CHKERRQ(ierr);
3239 	/* Otherwise A is extracted straight into (*submats)[i]. */
3240 	/* TODO: Compose A[i] on (*submat([i] for future use, if ((isrow_p[i] || iscol_p[i]) && MAT_INITIAL_MATRIX). */
3241 	ierr = MatDestroy(A+i);CHKERRQ(ierr);
3242       } else (*submat)[i] = A[i];
3243     }
3244     ierr = ISDestroy(&isrow_p[i]);CHKERRQ(ierr);
3245     ierr = ISDestroy(&iscol_p[i]);CHKERRQ(ierr);
3246   }
3247   ierr = PetscFree2(cisrow,ciscol);CHKERRQ(ierr);
3248   ierr = PetscFree2(isrow_p,iscol_p);CHKERRQ(ierr);
3249   ierr = PetscFree(ciscol_p);CHKERRQ(ierr);
3250   ierr = PetscFree(A);CHKERRQ(ierr);
3251   ierr = PetscFree(B);CHKERRQ(ierr);
3252   PetscFunctionReturn(0);
3253 }
3254 
3255 PetscErrorCode MatGetSubMatricesMPI_MPIAIJ(Mat C,PetscInt ismax,const IS isrow[],const IS iscol[],MatReuse scall,Mat *submat[])
3256 {
3257   PetscErrorCode ierr;
3258 
3259   PetscFunctionBegin;
3260   ierr = MatGetSubMatricesMPI_MPIXAIJ(C,ismax,isrow,iscol,scall,submat,MatGetSubMatrices_MPIAIJ,MatGetSeqMats_MPIAIJ,MatSetSeqMat_SeqAIJ,MatSetSeqMats_MPIAIJ);CHKERRQ(ierr);
3261   PetscFunctionReturn(0);
3262 }
3263