xref: /petsc/src/ksp/pc/impls/bddc/bddcschurs.c (revision 1d850880d03c2bfed1702a6bd79de4aa72605b96)
1 #include <../src/ksp/pc/impls/bddc/bddc.h>
2 #include <../src/ksp/pc/impls/bddc/bddcprivate.h>
3 
4 static PetscErrorCode PCBDDCAdjGetNextLayer_Private(PetscInt*,PetscInt,PetscBT,PetscInt*,PetscInt*,PetscInt*);
5 
6 #undef __FUNCT__
7 #define __FUNCT__ "PCBDDCSubSchursSetUpNew"
8 PetscErrorCode PCBDDCSubSchursSetUpNew(PCBDDCSubSchurs sub_schurs, PetscInt xadj[], PetscInt adjncy[], PetscInt nlayers)
9 {
10   Mat                    A_II,A_IB,A_BI,A_BB;
11   Mat                    AE_II,*AE_IE,*AE_EI,*AE_EE;
12   Mat                    global_schur_subsets,*submat_global_schur_subsets,work_mat;
13   ISLocalToGlobalMapping l2gmap_subsets;
14   IS                     is_I,*is_subset_B,temp_is;
15   PetscInt               *nnz,*all_local_idx_G,*all_local_idx_B,*all_local_idx_N,*all_permutation_G;
16   PetscInt               i,subset_size,max_subset_size;
17   PetscInt               local_size,global_size;
18   PetscBool              implicit_schurs;
19   PetscErrorCode         ierr;
20 
21   PetscFunctionBegin;
22   //ierr = PetscObjectTypeCompare((PetscObject)sub_schurs->S,MATSCHURCOMPLEMENT,&implicit_schurs);CHKERRQ(ierr);
23   implicit_schurs = PETSC_TRUE;
24   /* allocate space for schur complements */
25   ierr = PetscMalloc4(sub_schurs->n_subs,&sub_schurs->is_AEj_B,
26                       sub_schurs->n_subs,&sub_schurs->S_Ej,
27                       sub_schurs->n_subs,&sub_schurs->work1,
28                       sub_schurs->n_subs,&sub_schurs->work2);CHKERRQ(ierr);
29 
30   /* get Schur complement matrices */
31   if (implicit_schurs) {
32     ierr = MatSchurComplementGetSubMatrices(sub_schurs->S,&A_II,NULL,&A_IB,&A_BI,&A_BB);CHKERRQ(ierr);
33     ierr = PetscMalloc4(sub_schurs->n_subs,&is_subset_B,
34                         sub_schurs->n_subs,&AE_IE,
35                         sub_schurs->n_subs,&AE_EI,
36                         sub_schurs->n_subs,&AE_EE);CHKERRQ(ierr);
37   }
38 
39   /* determine interior problems */
40   if (nlayers >= 0 && xadj != NULL && adjncy != NULL) { /* Interior problems can be different from the original one */
41     PetscBT                touched;
42     const PetscInt*        idx_B;
43     PetscInt               n_I,n_B,n_local_dofs,n_prev_added,j,layer,*local_numbering;
44 
45     /* get sizes */
46     ierr = ISGetLocalSize(sub_schurs->is_I,&n_I);CHKERRQ(ierr);
47     ierr = ISGetLocalSize(sub_schurs->is_B,&n_B);CHKERRQ(ierr);
48 
49     ierr = PetscMalloc1(n_I+n_B,&local_numbering);CHKERRQ(ierr);
50     ierr = PetscBTCreate(n_I+n_B,&touched);CHKERRQ(ierr);
51     ierr = PetscBTMemzero(n_I+n_B,touched);CHKERRQ(ierr);
52 
53     /* all boundary dofs must be skipped when adding layers */
54     ierr = ISGetIndices(sub_schurs->is_B,&idx_B);CHKERRQ(ierr);
55     for (j=0;j<n_B;j++) {
56       ierr = PetscBTSet(touched,idx_B[j]);CHKERRQ(ierr);
57     }
58     ierr = PetscMemcpy(local_numbering,idx_B,n_B*sizeof(PetscInt));CHKERRQ(ierr);
59     ierr = ISRestoreIndices(sub_schurs->is_B,&idx_B);CHKERRQ(ierr);
60 
61     /* add prescribed number of layers of dofs */
62     n_local_dofs = n_B;
63     n_prev_added = n_B;
64     for (layer=0;layer<nlayers;layer++) {
65       PetscInt n_added;
66       if (n_local_dofs == n_I+n_B) break;
67       if (n_local_dofs > n_I+n_B) {
68         SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Error querying layer %d. Out of bound access (%d > %d)",layer,n_local_dofs,n_I+n_B);
69       }
70       ierr = PCBDDCAdjGetNextLayer_Private(local_numbering+n_local_dofs,n_prev_added,touched,xadj,adjncy,&n_added);CHKERRQ(ierr);
71       n_prev_added = n_added;
72       n_local_dofs += n_added;
73       if (!n_added) break;
74     }
75     ierr = PetscBTDestroy(&touched);CHKERRQ(ierr);
76 
77     /* IS for I dofs in original numbering */
78     ierr = ISCreateGeneral(PetscObjectComm((PetscObject)sub_schurs->is_I),n_local_dofs-n_B,local_numbering+n_B,PETSC_COPY_VALUES,&sub_schurs->is_I_layer);CHKERRQ(ierr);
79     ierr = PetscFree(local_numbering);CHKERRQ(ierr);
80     ierr = ISSort(sub_schurs->is_I_layer);CHKERRQ(ierr);
81     /* IS for I dofs in boundary numbering */
82     if (implicit_schurs) {
83       ISLocalToGlobalMapping ItoNmap;
84       ierr = ISLocalToGlobalMappingCreateIS(sub_schurs->is_I,&ItoNmap);CHKERRQ(ierr);
85       ierr = ISGlobalToLocalMappingApplyIS(ItoNmap,IS_GTOLM_DROP,sub_schurs->is_I_layer,&is_I);CHKERRQ(ierr);
86       ierr = ISLocalToGlobalMappingDestroy(&ItoNmap);CHKERRQ(ierr);
87 
88       /* II block */
89       ierr = MatGetSubMatrix(A_II,is_I,is_I,MAT_INITIAL_MATRIX,&AE_II);CHKERRQ(ierr);
90     }
91   } else {
92     PetscInt n_I;
93 
94     /* IS for I dofs in original numbering */
95     ierr = PetscObjectReference((PetscObject)sub_schurs->is_I);CHKERRQ(ierr);
96     sub_schurs->is_I_layer = sub_schurs->is_I;
97 
98     /* IS for I dofs in I numbering (strided 1) */
99     if (implicit_schurs) {
100       ierr = ISGetSize(sub_schurs->is_I,&n_I);CHKERRQ(ierr);
101       ierr = ISCreateStride(PetscObjectComm((PetscObject)sub_schurs->is_I),n_I,0,1,&is_I);CHKERRQ(ierr);
102 
103       /* II block is the same */
104       ierr = PetscObjectReference((PetscObject)A_II);CHKERRQ(ierr);
105       AE_II = A_II;
106     }
107   }
108 
109   if (implicit_schurs) {
110     /* subsets in original and boundary numbering */
111     for (i=0;i<sub_schurs->n_subs;i++) {
112       ierr = ISDuplicate(sub_schurs->is_subs[i],&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
113       ierr = ISSort(sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
114       ierr = ISGlobalToLocalMappingApplyIS(sub_schurs->BtoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_B[i],&is_subset_B[i]);CHKERRQ(ierr);
115     }
116 
117     /* EE block */
118     for (i=0;i<sub_schurs->n_subs;i++) {
119       ierr = MatGetSubMatrix(A_BB,is_subset_B[i],is_subset_B[i],MAT_INITIAL_MATRIX,&AE_EE[i]);CHKERRQ(ierr);
120     }
121     /* IE block */
122     for (i=0;i<sub_schurs->n_subs;i++) {
123       ierr = MatGetSubMatrix(A_IB,is_I,is_subset_B[i],MAT_INITIAL_MATRIX,&AE_IE[i]);CHKERRQ(ierr);
124     }
125     /* EI block */
126     for (i=0;i<sub_schurs->n_subs;i++) {
127       ierr = MatGetSubMatrix(A_BI,is_subset_B[i],is_I,MAT_INITIAL_MATRIX,&AE_EI[i]);CHKERRQ(ierr);
128     }
129 
130     /* setup Schur complements on subset */
131     for (i=0;i<sub_schurs->n_subs;i++) {
132       ierr = MatCreateSchurComplement(AE_II,AE_II,AE_IE[i],AE_EI[i],AE_EE[i],&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
133       if (AE_II == A_II) { /* we can reuse the same ksp */
134         KSP ksp;
135         ierr = MatSchurComplementGetKSP(sub_schurs->S,&ksp);CHKERRQ(ierr);
136         ierr = MatSchurComplementSetKSP(sub_schurs->S_Ej[i],ksp);CHKERRQ(ierr);
137       } else { /* build new ksp object which inherits ksp and pc types from the original one */
138         KSP      origksp,schurksp;
139         PC       origpc,schurpc;
140         KSPType  ksp_type;
141         PCType   pc_type;
142         PetscInt n_internal;
143 
144         ierr = MatSchurComplementGetKSP(sub_schurs->S,&origksp);CHKERRQ(ierr);
145         ierr = MatSchurComplementGetKSP(sub_schurs->S_Ej[i],&schurksp);CHKERRQ(ierr);
146         ierr = KSPGetType(origksp,&ksp_type);CHKERRQ(ierr);
147         ierr = KSPSetType(schurksp,ksp_type);CHKERRQ(ierr);
148         ierr = KSPGetPC(schurksp,&schurpc);CHKERRQ(ierr);
149         ierr = KSPGetPC(origksp,&origpc);CHKERRQ(ierr);
150         ierr = PCGetType(origpc,&pc_type);CHKERRQ(ierr);
151         ierr = PCSetType(schurpc,pc_type);CHKERRQ(ierr);
152         ierr = ISGetSize(is_I,&n_internal);CHKERRQ(ierr);
153         if (n_internal) { /* UMFPACK gives error with 0 sized problems */
154           MatSolverPackage solver=NULL;
155           ierr = PCFactorGetMatSolverPackage(origpc,(const MatSolverPackage*)&solver);CHKERRQ(ierr);
156           if (solver) {
157             ierr = PCFactorSetMatSolverPackage(schurpc,solver);CHKERRQ(ierr);
158           }
159         }
160         ierr = KSPSetUp(schurksp);CHKERRQ(ierr);
161       }
162     }
163     /* free */
164     ierr = ISDestroy(&is_I);CHKERRQ(ierr);
165     ierr = MatDestroy(&AE_II);CHKERRQ(ierr);
166     for (i=0;i<sub_schurs->n_subs;i++) {
167       ierr = MatDestroy(&AE_EE[i]);CHKERRQ(ierr);
168       ierr = MatDestroy(&AE_IE[i]);CHKERRQ(ierr);
169       ierr = MatDestroy(&AE_EI[i]);CHKERRQ(ierr);
170       ierr = ISDestroy(&is_subset_B[i]);CHKERRQ(ierr);
171     }
172     ierr = PetscFree4(is_subset_B,AE_IE,AE_EI,AE_EE);CHKERRQ(ierr);
173   }
174 
175   /* TODO: just for compatibility with the previous version, needs to be fixed */
176   for (i=0;i<sub_schurs->n_subs_par;i++) {
177     PetscInt j = sub_schurs->index_parallel[i];
178     ierr = MatCreateVecs(sub_schurs->S_Ej[j],&sub_schurs->work1[j],&sub_schurs->work2[j]);CHKERRQ(ierr);
179   }
180   for (i=0;i<sub_schurs->n_subs_seq;i++) {
181      sub_schurs->work1[sub_schurs->index_sequential[i]] = 0;
182      sub_schurs->work2[sub_schurs->index_sequential[i]] = 0;
183   }
184 
185   if (!sub_schurs->n_subs_seq_g) {
186     sub_schurs->S_Ej_all = 0;
187     sub_schurs->sum_S_Ej_all = 0;
188     sub_schurs->is_Ej_all = 0;
189     PetscFunctionReturn(0);
190   }
191 
192   /* Get info on subset sizes and sum of all subsets sizes */
193   max_subset_size = 0;
194   local_size = 0;
195   for (i=0;i<sub_schurs->n_subs_seq;i++) {
196     PetscInt j = sub_schurs->index_sequential[i];
197     ierr = ISGetLocalSize(sub_schurs->is_AEj_B[j],&subset_size);CHKERRQ(ierr);
198     max_subset_size = PetscMax(subset_size,max_subset_size);
199     local_size += subset_size;
200   }
201 
202   /* Work arrays for local indices */
203   ierr = PetscMalloc1(local_size,&all_local_idx_B);CHKERRQ(ierr);
204   ierr = PetscMalloc1(local_size,&all_local_idx_N);CHKERRQ(ierr);
205   ierr = PetscMalloc1(local_size,&nnz);CHKERRQ(ierr);
206 
207   /* Get local indices in local whole numbering and local boundary numbering */
208   local_size = 0;
209   for (i=0;i<sub_schurs->n_subs_seq;i++) {
210     PetscInt j;
211     const    PetscInt *idxs;
212 
213     PetscInt local_problem_index = sub_schurs->index_sequential[i];
214     ierr = ISGetLocalSize(sub_schurs->is_AEj_B[local_problem_index],&subset_size);CHKERRQ(ierr);
215     ierr = ISGetIndices(sub_schurs->is_AEj_B[local_problem_index],&idxs);CHKERRQ(ierr);
216     /* subset indices in local numbering */
217     ierr = PetscMemcpy(all_local_idx_N+local_size,idxs,subset_size*sizeof(PetscInt));CHKERRQ(ierr);
218     ierr = ISRestoreIndices(sub_schurs->is_AEj_B[local_problem_index],&idxs);CHKERRQ(ierr);
219     for (j=0;j<subset_size;j++) nnz[local_size+j] = subset_size;
220     local_size += subset_size;
221   }
222 
223   /* subset indices in local boundary numbering */
224   ierr = ISGlobalToLocalMappingApply(sub_schurs->BtoNmap,IS_GTOLM_DROP,local_size,all_local_idx_N,&subset_size,all_local_idx_B);CHKERRQ(ierr);
225   if (subset_size != local_size) {
226     SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Error in sub_schurs serial (BtoNmap)! %d != %d\n",subset_size,local_size);
227   }
228   ierr = ISCreateGeneral(PETSC_COMM_SELF,local_size,all_local_idx_B,PETSC_OWN_POINTER,&sub_schurs->is_Ej_all);CHKERRQ(ierr);
229 
230   /* Number dofs on all subsets (parallel) and sort numbering */
231   ierr = PCBDDCSubsetNumbering(PetscObjectComm((PetscObject)sub_schurs->l2gmap),sub_schurs->l2gmap,local_size,all_local_idx_N,PETSC_NULL,&global_size,&all_local_idx_G);CHKERRQ(ierr);
232   ierr = PetscMalloc1(local_size,&all_permutation_G);CHKERRQ(ierr);
233   for (i=0;i<local_size;i++) {
234     all_permutation_G[i]=i;
235   }
236   ierr = PetscSortIntWithPermutation(local_size,all_local_idx_G,all_permutation_G);CHKERRQ(ierr);
237 
238   /* Local matrix of all local Schur on subsets */
239   ierr = MatCreate(PETSC_COMM_SELF,&sub_schurs->S_Ej_all);CHKERRQ(ierr);
240   ierr = MatSetSizes(sub_schurs->S_Ej_all,PETSC_DECIDE,PETSC_DECIDE,local_size,local_size);CHKERRQ(ierr);
241   ierr = MatSetType(sub_schurs->S_Ej_all,MATAIJ);CHKERRQ(ierr);
242   ierr = MatSeqAIJSetPreallocation(sub_schurs->S_Ej_all,0,nnz);CHKERRQ(ierr);
243   ierr = PetscFree(nnz);CHKERRQ(ierr);
244 
245   if (implicit_schurs) {
246     PetscScalar *fill_vals;
247     PetscInt    *dummy_idx;
248 
249     /* Work arrays */
250     ierr = PetscMalloc2(max_subset_size,&dummy_idx,max_subset_size*max_subset_size,&fill_vals);CHKERRQ(ierr);
251 
252     /* Loop on local problems to compute Schur complements explicitly (TODO; optimize)*/
253     local_size = 0;
254     for (i=0;i<sub_schurs->n_subs_seq;i++) {
255       Vec work1,work2;
256       PetscInt j,local_problem_index = sub_schurs->index_sequential[i];
257 
258       ierr = MatCreateVecs(sub_schurs->S_Ej[local_problem_index],&work1,&work2);CHKERRQ(ierr);
259       ierr = ISGetLocalSize(sub_schurs->is_AEj_B[local_problem_index],&subset_size);CHKERRQ(ierr);
260       /* local Schur */
261       for (j=0;j<subset_size;j++) {
262         ierr = VecSet(work1,0.0);CHKERRQ(ierr);
263         ierr = VecSetValue(work1,j,1.0,INSERT_VALUES);CHKERRQ(ierr);
264         ierr = VecPlaceArray(work2,&fill_vals[j*subset_size]);CHKERRQ(ierr);
265         ierr = MatMult(sub_schurs->S_Ej[local_problem_index],work1,work2);CHKERRQ(ierr);
266         ierr = VecResetArray(work2);CHKERRQ(ierr);
267       }
268       for (j=0;j<subset_size;j++) {
269         dummy_idx[j]=local_size+j;
270       }
271       ierr = MatSetValues(sub_schurs->S_Ej_all,subset_size,dummy_idx,subset_size,dummy_idx,fill_vals,INSERT_VALUES);CHKERRQ(ierr);
272       local_size += subset_size;
273       ierr = VecDestroy(&work1);CHKERRQ(ierr);
274       ierr = VecDestroy(&work2);CHKERRQ(ierr);
275     }
276     ierr = PetscFree2(dummy_idx,fill_vals);CHKERRQ(ierr);
277   }
278   ierr = MatAssemblyBegin(sub_schurs->S_Ej_all,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
279   ierr = MatAssemblyEnd(sub_schurs->S_Ej_all,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
280 
281   /* Global matrix of all assembled Schur on subsets */
282   ierr = ISLocalToGlobalMappingCreate(PetscObjectComm((PetscObject)sub_schurs->l2gmap),1,local_size,all_local_idx_G,PETSC_COPY_VALUES,&l2gmap_subsets);CHKERRQ(ierr);
283   ierr = MatCreateIS(PetscObjectComm((PetscObject)sub_schurs->l2gmap),1,PETSC_DECIDE,PETSC_DECIDE,global_size,global_size,l2gmap_subsets,&work_mat);CHKERRQ(ierr);
284   ierr = ISLocalToGlobalMappingDestroy(&l2gmap_subsets);CHKERRQ(ierr);
285   ierr = MatISSetLocalMat(work_mat,sub_schurs->S_Ej_all);CHKERRQ(ierr);
286   ierr = MatISGetMPIXAIJ(work_mat,MAT_INITIAL_MATRIX,&global_schur_subsets);CHKERRQ(ierr);
287   ierr = MatDestroy(&work_mat);CHKERRQ(ierr);
288 
289   /* Get local part of (\sum_j S_Ej) */
290   for (i=0;i<local_size;i++) {
291     all_local_idx_N[i] = all_local_idx_G[all_permutation_G[i]];
292   }
293   ierr = ISCreateGeneral(PetscObjectComm((PetscObject)sub_schurs->l2gmap),local_size,all_local_idx_N,PETSC_OWN_POINTER,&temp_is);CHKERRQ(ierr);
294   ierr = MatGetSubMatrices(global_schur_subsets,1,&temp_is,&temp_is,MAT_INITIAL_MATRIX,&submat_global_schur_subsets);CHKERRQ(ierr);
295   ierr = MatDestroy(&global_schur_subsets);CHKERRQ(ierr);
296   ierr = ISDestroy(&temp_is);CHKERRQ(ierr);
297   for (i=0;i<local_size;i++) {
298     all_local_idx_G[all_permutation_G[i]] = i;
299   }
300   ierr = ISCreateGeneral(PETSC_COMM_SELF,local_size,all_local_idx_G,PETSC_OWN_POINTER,&temp_is);CHKERRQ(ierr);
301   ierr = ISSetPermutation(temp_is);CHKERRQ(ierr);
302   ierr = MatPermute(submat_global_schur_subsets[0],temp_is,temp_is,&sub_schurs->sum_S_Ej_all);CHKERRQ(ierr);
303   ierr = MatDestroyMatrices(1,&submat_global_schur_subsets);CHKERRQ(ierr);
304   ierr = ISDestroy(&temp_is);CHKERRQ(ierr);
305   ierr = PetscFree(all_permutation_G);CHKERRQ(ierr);
306   PetscFunctionReturn(0);
307 }
308 
309 #undef __FUNCT__
310 #define __FUNCT__ "PCBDDCSubSchursInit"
311 PetscErrorCode PCBDDCSubSchursInit(PCBDDCSubSchurs sub_schurs, Mat A, Mat S, IS is_I, IS is_B, PCBDDCGraph graph, ISLocalToGlobalMapping BtoNmap, PetscInt seqthreshold)
312 {
313   IS                  *faces,*edges,*all_cc;
314   PetscInt            *index_sequential,*index_parallel;
315   PetscInt            *auxlocal_sequential,*auxlocal_parallel;
316   PetscInt            *auxglobal_sequential,*auxglobal_parallel;
317   PetscInt            *auxmapping;//,*idxs;
318   PetscInt            i,max_subset_size;
319   PetscInt            n_sequential_problems,n_local_sequential_problems,n_parallel_problems,n_local_parallel_problems;
320   PetscInt            n_faces,n_edges,n_all_cc;
321   PetscBool           is_sorted;
322   PetscErrorCode  ierr;
323 
324   PetscFunctionBegin;
325   ierr = ISSorted(is_I,&is_sorted);CHKERRQ(ierr);
326   if (!is_sorted) {
327     SETERRQ(PetscObjectComm((PetscObject)is_I),PETSC_ERR_PLIB,"IS for I dofs should be shorted");
328   }
329   ierr = ISSorted(is_B,&is_sorted);CHKERRQ(ierr);
330   if (!is_sorted) {
331     SETERRQ(PetscObjectComm((PetscObject)is_B),PETSC_ERR_PLIB,"IS for B dofs should be shorted");
332   }
333 
334   /* reset any previous data */
335   ierr = PCBDDCSubSchursReset(sub_schurs);CHKERRQ(ierr);
336 
337   /* get index sets for faces and edges */
338   ierr = PCBDDCGraphGetCandidatesIS(graph,&n_faces,&faces,&n_edges,&edges,NULL);CHKERRQ(ierr);
339   n_all_cc = n_faces+n_edges;
340   ierr = PetscMalloc1(n_all_cc,&all_cc);CHKERRQ(ierr);
341   for (i=0;i<n_faces;i++) {
342     all_cc[i] = faces[i];
343   }
344   for (i=0;i<n_edges;i++) {
345     all_cc[n_faces+i] = edges[i];
346   }
347   ierr = PetscFree(faces);CHKERRQ(ierr);
348   ierr = PetscFree(edges);CHKERRQ(ierr);
349 
350   /* map interface's subsets */
351   max_subset_size = 0;
352   for (i=0;i<n_all_cc;i++) {
353     PetscInt subset_size;
354     ierr = ISGetLocalSize(all_cc[i],&subset_size);CHKERRQ(ierr);
355     max_subset_size = PetscMax(max_subset_size,subset_size);
356   }
357   ierr = PetscMalloc1(max_subset_size,&auxmapping);CHKERRQ(ierr);
358   ierr = PetscMalloc2(graph->ncc,&auxlocal_sequential,
359                       graph->ncc,&auxlocal_parallel);CHKERRQ(ierr);
360   ierr = PetscMalloc2(graph->ncc,&index_sequential,
361                       graph->ncc,&index_parallel);CHKERRQ(ierr);
362 
363   /* if threshold is negative, uses all sequential problems */
364   if (seqthreshold < 0) seqthreshold = max_subset_size;
365 
366   /* determine which problem has to be solved in parallel or sequentially */
367   n_local_sequential_problems = 0;
368   n_local_parallel_problems = 0;
369   for (i=0;i<n_all_cc;i++) {
370     PetscInt       subset_size,j,min_loc = 0;
371     const PetscInt *idxs;
372 
373     ierr = ISGetLocalSize(all_cc[i],&subset_size);CHKERRQ(ierr);
374     ierr = ISGetIndices(all_cc[i],&idxs);CHKERRQ(ierr);
375     ierr = ISLocalToGlobalMappingApply(graph->l2gmap,subset_size,idxs,auxmapping);CHKERRQ(ierr);
376     for (j=1;j<subset_size;j++) {
377       if (auxmapping[j]<auxmapping[min_loc]) {
378         min_loc = j;
379       }
380     }
381     if (subset_size > seqthreshold) {
382       index_parallel[n_local_parallel_problems] = i;
383       auxlocal_parallel[n_local_parallel_problems] = idxs[min_loc];
384       n_local_parallel_problems++;
385     } else {
386       index_sequential[n_local_sequential_problems] = i;
387       auxlocal_sequential[n_local_sequential_problems] = idxs[min_loc];
388       n_local_sequential_problems++;
389     }
390     ierr = ISRestoreIndices(all_cc[i],&idxs);CHKERRQ(ierr);
391   }
392 
393   /* Number parallel problems */
394   auxglobal_parallel = 0;
395   ierr = PCBDDCSubsetNumbering(PetscObjectComm((PetscObject)graph->l2gmap),graph->l2gmap,n_local_parallel_problems,auxlocal_parallel,PETSC_NULL,&n_parallel_problems,&auxglobal_parallel);CHKERRQ(ierr);
396 
397   /* Number sequential problems */
398   auxglobal_sequential = 0;
399   ierr = PCBDDCSubsetNumbering(PetscObjectComm((PetscObject)graph->l2gmap),graph->l2gmap,n_local_sequential_problems,auxlocal_sequential,PETSC_NULL,&n_sequential_problems,&auxglobal_sequential);CHKERRQ(ierr);
400 
401   /* update info in sub_schurs */
402   if (A) {
403     ierr = PetscObjectReference((PetscObject)A);CHKERRQ(ierr);
404     sub_schurs->A = A;
405   }
406   ierr = PetscObjectReference((PetscObject)S);CHKERRQ(ierr);
407   sub_schurs->S = S;
408   ierr = PetscObjectReference((PetscObject)is_I);CHKERRQ(ierr);
409   sub_schurs->is_I = is_I;
410   ierr = PetscObjectReference((PetscObject)is_B);CHKERRQ(ierr);
411   sub_schurs->is_B = is_B;
412   ierr = PetscObjectReference((PetscObject)graph->l2gmap);CHKERRQ(ierr);
413   sub_schurs->l2gmap = graph->l2gmap;
414   ierr = PetscObjectReference((PetscObject)BtoNmap);CHKERRQ(ierr);
415   sub_schurs->BtoNmap = BtoNmap;
416   sub_schurs->n_subs_seq = n_local_sequential_problems;
417   sub_schurs->n_subs_par = n_local_parallel_problems;
418   sub_schurs->n_subs_seq_g = n_sequential_problems;
419   sub_schurs->n_subs_par_g = n_parallel_problems;
420   sub_schurs->n_subs = sub_schurs->n_subs_seq + sub_schurs->n_subs_par;
421   sub_schurs->is_subs = all_cc;
422   sub_schurs->index_sequential = index_sequential;
423   sub_schurs->index_parallel = index_parallel;
424   sub_schurs->auxglobal_sequential = auxglobal_sequential;
425   sub_schurs->auxglobal_parallel = auxglobal_parallel;
426 
427   /* free workspace */
428   ierr = PetscFree(auxmapping);CHKERRQ(ierr);
429   ierr = PetscFree2(auxlocal_sequential,auxlocal_parallel);CHKERRQ(ierr);
430 
431   PetscFunctionReturn(0);
432 }
433 
434 #undef __FUNCT__
435 #define __FUNCT__ "PCBDDCSubSchursCreate"
436 PetscErrorCode PCBDDCSubSchursCreate(PCBDDCSubSchurs *sub_schurs)
437 {
438   PCBDDCSubSchurs schurs_ctx;
439   PetscErrorCode  ierr;
440 
441   PetscFunctionBegin;
442   ierr = PetscNew(&schurs_ctx);CHKERRQ(ierr);
443   schurs_ctx->n_subs = 0;
444   *sub_schurs = schurs_ctx;
445   PetscFunctionReturn(0);
446 }
447 
448 #undef __FUNCT__
449 #define __FUNCT__ "PCBDDCSubSchursDestroy"
450 PetscErrorCode PCBDDCSubSchursDestroy(PCBDDCSubSchurs *sub_schurs)
451 {
452   PetscErrorCode ierr;
453 
454   PetscFunctionBegin;
455   ierr = PCBDDCSubSchursReset(*sub_schurs);CHKERRQ(ierr);
456   ierr = PetscFree(*sub_schurs);CHKERRQ(ierr);
457   PetscFunctionReturn(0);
458 }
459 
460 #undef __FUNCT__
461 #define __FUNCT__ "PCBDDCSubSchursReset"
462 PetscErrorCode PCBDDCSubSchursReset(PCBDDCSubSchurs sub_schurs)
463 {
464   PetscInt       i;
465   PetscErrorCode ierr;
466 
467   PetscFunctionBegin;
468   ierr = MatDestroy(&sub_schurs->A);CHKERRQ(ierr);
469   ierr = MatDestroy(&sub_schurs->S);CHKERRQ(ierr);
470   ierr = ISDestroy(&sub_schurs->is_I);CHKERRQ(ierr);
471   ierr = ISDestroy(&sub_schurs->is_B);CHKERRQ(ierr);
472   ierr = ISLocalToGlobalMappingDestroy(&sub_schurs->l2gmap);CHKERRQ(ierr);
473   ierr = ISLocalToGlobalMappingDestroy(&sub_schurs->BtoNmap);CHKERRQ(ierr);
474   ierr = MatDestroy(&sub_schurs->S_Ej_all);CHKERRQ(ierr);
475   ierr = MatDestroy(&sub_schurs->sum_S_Ej_all);CHKERRQ(ierr);
476   ierr = ISDestroy(&sub_schurs->is_Ej_all);CHKERRQ(ierr);
477   for (i=0;i<sub_schurs->n_subs;i++) {
478     ierr = ISDestroy(&sub_schurs->is_subs[i]);CHKERRQ(ierr);
479     ierr = ISDestroy(&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
480     ierr = MatDestroy(&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
481     ierr = VecDestroy(&sub_schurs->work1[i]);CHKERRQ(ierr);
482     ierr = VecDestroy(&sub_schurs->work2[i]);CHKERRQ(ierr);
483   }
484   ierr = ISDestroy(&sub_schurs->is_I_layer);CHKERRQ(ierr);
485   if (sub_schurs->n_subs) {
486     ierr = PetscFree(sub_schurs->is_subs);CHKERRQ(ierr);
487     ierr = PetscFree4(sub_schurs->is_AEj_B,sub_schurs->S_Ej,sub_schurs->work1,sub_schurs->work2);CHKERRQ(ierr);
488     ierr = PetscFree2(sub_schurs->index_sequential,sub_schurs->index_parallel);CHKERRQ(ierr);
489     ierr = PetscFree(sub_schurs->auxglobal_sequential);CHKERRQ(ierr);
490     ierr = PetscFree(sub_schurs->auxglobal_parallel);CHKERRQ(ierr);
491   }
492   sub_schurs->n_subs = 0;
493   PetscFunctionReturn(0);
494 }
495 
496 #undef __FUNCT__
497 #define __FUNCT__ "PCBDDCAdjGetNextLayer_Private"
498 PETSC_STATIC_INLINE PetscErrorCode PCBDDCAdjGetNextLayer_Private(PetscInt* queue_tip,PetscInt n_prev,PetscBT touched,PetscInt* xadj,PetscInt* adjncy,PetscInt* n_added)
499 {
500   PetscInt       i,j,n;
501   PetscErrorCode ierr;
502 
503   PetscFunctionBegin;
504   n = 0;
505   for (i=-n_prev;i<0;i++) {
506     PetscInt start_dof = queue_tip[i];
507     for (j=xadj[start_dof];j<xadj[start_dof+1];j++) {
508       PetscInt dof = adjncy[j];
509       if (!PetscBTLookup(touched,dof)) {
510         ierr = PetscBTSet(touched,dof);CHKERRQ(ierr);
511         queue_tip[n] = dof;
512         n++;
513       }
514     }
515   }
516   *n_added = n;
517   PetscFunctionReturn(0);
518 }
519 
520 #undef __FUNCT__
521 #define __FUNCT__ "PCBDDCSubSchursSetUp"
522 PetscErrorCode PCBDDCSubSchursSetUp(PCBDDCSubSchurs sub_schurs, Mat S, IS is_A_I, IS is_A_B, PetscInt ncc, IS is_cc[], PetscInt xadj[], PetscInt adjncy[], PetscInt nlayers)
523 {
524   Mat                    A_II,A_IB,A_BI,A_BB;
525   Mat                    AE_II,*AE_IE,*AE_EI,*AE_EE;
526   IS                     is_I,*is_subset_B;
527   ISLocalToGlobalMapping BtoNmap;
528   PetscInt               i;
529   PetscBool              is_sorted;
530   PetscErrorCode         ierr;
531 
532   PetscFunctionBegin;
533   ierr = ISSorted(is_A_I,&is_sorted);CHKERRQ(ierr);
534   if (!is_sorted) {
535     SETERRQ(PetscObjectComm((PetscObject)is_A_I),PETSC_ERR_PLIB,"IS for I dofs should be shorted");
536   }
537   ierr = ISSorted(is_A_B,&is_sorted);CHKERRQ(ierr);
538   if (!is_sorted) {
539     SETERRQ(PetscObjectComm((PetscObject)is_A_B),PETSC_ERR_PLIB,"IS for B dofs should be shorted");
540   }
541 
542   /* get Schur complement matrices */
543   ierr = MatSchurComplementGetSubMatrices(S,&A_II,NULL,&A_IB,&A_BI,&A_BB);CHKERRQ(ierr);
544 
545   /* allocate space for schur complements */
546   sub_schurs->n_subs = ncc;
547   ierr = PetscMalloc4(sub_schurs->n_subs,&sub_schurs->is_AEj_B,
548                       sub_schurs->n_subs,&sub_schurs->S_Ej,
549                       sub_schurs->n_subs,&sub_schurs->work1,
550                       sub_schurs->n_subs,&sub_schurs->work2);CHKERRQ(ierr);
551   ierr = PetscMalloc4(ncc,&is_subset_B,ncc,&AE_IE,ncc,&AE_EI,ncc,&AE_EE);CHKERRQ(ierr);
552 
553   /* maps */
554   if (sub_schurs->n_subs && nlayers >= 0 && xadj != NULL && adjncy != NULL) { /* Interior problems can be different from the original one */
555     ISLocalToGlobalMapping ItoNmap;
556     PetscBT                touched;
557     const PetscInt*        idx_B;
558     PetscInt               n_I,n_B,n_local_dofs,n_prev_added,j,layer,*local_numbering;
559 
560     /* get sizes */
561     ierr = ISGetLocalSize(is_A_I,&n_I);CHKERRQ(ierr);
562     ierr = ISGetLocalSize(is_A_B,&n_B);CHKERRQ(ierr);
563 
564     ierr = ISLocalToGlobalMappingCreateIS(is_A_I,&ItoNmap);CHKERRQ(ierr);
565     ierr = PetscMalloc1(n_I+n_B,&local_numbering);CHKERRQ(ierr);
566     ierr = PetscBTCreate(n_I+n_B,&touched);CHKERRQ(ierr);
567     ierr = PetscBTMemzero(n_I+n_B,touched);CHKERRQ(ierr);
568 
569     /* all boundary dofs must be skipped when adding layers */
570     ierr = ISGetIndices(is_A_B,&idx_B);CHKERRQ(ierr);
571     for (j=0;j<n_B;j++) {
572       ierr = PetscBTSet(touched,idx_B[j]);CHKERRQ(ierr);
573     }
574     ierr = PetscMemcpy(local_numbering,idx_B,n_B*sizeof(PetscInt));CHKERRQ(ierr);
575     ierr = ISRestoreIndices(is_A_B,&idx_B);CHKERRQ(ierr);
576 
577     /* add next layers of dofs */
578     n_local_dofs = n_B;
579     n_prev_added = n_B;
580     for (layer=0;layer<nlayers;layer++) {
581       PetscInt n_added;
582       if (n_local_dofs == n_I+n_B) break;
583       if (n_local_dofs > n_I+n_B) {
584         SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Error querying layer %d. Out of bound access (%d > %d)",layer,n_local_dofs,n_I+n_B);
585       }
586       ierr = PCBDDCAdjGetNextLayer_Private(local_numbering+n_local_dofs,n_prev_added,touched,xadj,adjncy,&n_added);CHKERRQ(ierr);
587       n_prev_added = n_added;
588       n_local_dofs += n_added;
589       if (!n_added) break;
590     }
591     ierr = PetscBTDestroy(&touched);CHKERRQ(ierr);
592 
593     /* IS for I dofs in original numbering and in I numbering */
594     ierr = ISCreateGeneral(PetscObjectComm((PetscObject)ItoNmap),n_local_dofs-n_B,local_numbering+n_B,PETSC_COPY_VALUES,&sub_schurs->is_I_layer);CHKERRQ(ierr);
595     ierr = PetscFree(local_numbering);CHKERRQ(ierr);
596     ierr = ISSort(sub_schurs->is_I_layer);CHKERRQ(ierr);
597     ierr = ISGlobalToLocalMappingApplyIS(ItoNmap,IS_GTOLM_DROP,sub_schurs->is_I_layer,&is_I);CHKERRQ(ierr);
598     ierr = ISLocalToGlobalMappingDestroy(&ItoNmap);CHKERRQ(ierr);
599 
600     /* II block */
601     ierr = MatGetSubMatrix(A_II,is_I,is_I,MAT_INITIAL_MATRIX,&AE_II);CHKERRQ(ierr);
602   } else {
603     PetscInt n_I;
604 
605     /* IS for I dofs in original numbering */
606     ierr = PetscObjectReference((PetscObject)is_A_I);CHKERRQ(ierr);
607     sub_schurs->is_I_layer = is_A_I;
608 
609     /* IS for I dofs in I numbering (strided 1) */
610     ierr = ISGetSize(is_A_I,&n_I);CHKERRQ(ierr);
611     ierr = ISCreateStride(PetscObjectComm((PetscObject)is_A_I),n_I,0,1,&is_I);CHKERRQ(ierr);
612 
613     /* II block is the same */
614     ierr = PetscObjectReference((PetscObject)A_II);CHKERRQ(ierr);
615     AE_II = A_II;
616   }
617 
618   /* subsets in original and boundary numbering */
619   ierr = ISLocalToGlobalMappingCreateIS(is_A_B,&BtoNmap);CHKERRQ(ierr);
620   for (i=0;i<sub_schurs->n_subs;i++) {
621     ierr = ISDuplicate(is_cc[i],&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
622     ierr = ISSort(sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
623     ierr = ISGlobalToLocalMappingApplyIS(BtoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_B[i],&is_subset_B[i]);CHKERRQ(ierr);
624   }
625   ierr = ISLocalToGlobalMappingDestroy(&BtoNmap);CHKERRQ(ierr);
626 
627   /* EE block */
628   for (i=0;i<sub_schurs->n_subs;i++) {
629     ierr = MatGetSubMatrix(A_BB,is_subset_B[i],is_subset_B[i],MAT_INITIAL_MATRIX,&AE_EE[i]);CHKERRQ(ierr);
630   }
631   /* IE block */
632   for (i=0;i<sub_schurs->n_subs;i++) {
633     ierr = MatGetSubMatrix(A_IB,is_I,is_subset_B[i],MAT_INITIAL_MATRIX,&AE_IE[i]);CHKERRQ(ierr);
634   }
635   /* EI block */
636   for (i=0;i<sub_schurs->n_subs;i++) {
637     ierr = MatGetSubMatrix(A_BI,is_subset_B[i],is_I,MAT_INITIAL_MATRIX,&AE_EI[i]);CHKERRQ(ierr);
638   }
639 
640   /* setup Schur complements on subset */
641   for (i=0;i<sub_schurs->n_subs;i++) {
642     ierr = MatCreateSchurComplement(AE_II,AE_II,AE_IE[i],AE_EI[i],AE_EE[i],&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
643     ierr = MatCreateVecs(sub_schurs->S_Ej[i],&sub_schurs->work1[i],&sub_schurs->work2[i]);CHKERRQ(ierr);
644     if (AE_II == A_II) { /* we can reuse the same ksp */
645       KSP ksp;
646       ierr = MatSchurComplementGetKSP(S,&ksp);CHKERRQ(ierr);
647       ierr = MatSchurComplementSetKSP(sub_schurs->S_Ej[i],ksp);CHKERRQ(ierr);
648     } else { /* build new ksp object which inherits ksp and pc types from the original one */
649       KSP      origksp,schurksp;
650       PC       origpc,schurpc;
651       KSPType  ksp_type;
652       PCType   pc_type;
653       PetscInt n_internal;
654 
655       ierr = MatSchurComplementGetKSP(S,&origksp);CHKERRQ(ierr);
656       ierr = MatSchurComplementGetKSP(sub_schurs->S_Ej[i],&schurksp);CHKERRQ(ierr);
657       ierr = KSPGetType(origksp,&ksp_type);CHKERRQ(ierr);
658       ierr = KSPSetType(schurksp,ksp_type);CHKERRQ(ierr);
659       ierr = KSPGetPC(schurksp,&schurpc);CHKERRQ(ierr);
660       ierr = KSPGetPC(origksp,&origpc);CHKERRQ(ierr);
661       ierr = PCGetType(origpc,&pc_type);CHKERRQ(ierr);
662       ierr = PCSetType(schurpc,pc_type);CHKERRQ(ierr);
663       ierr = ISGetSize(is_I,&n_internal);CHKERRQ(ierr);
664       if (n_internal) { /* UMFPACK gives error with 0 sized problems */
665         MatSolverPackage solver=NULL;
666         ierr = PCFactorGetMatSolverPackage(origpc,(const MatSolverPackage*)&solver);CHKERRQ(ierr);
667         if (solver) {
668           ierr = PCFactorSetMatSolverPackage(schurpc,solver);CHKERRQ(ierr);
669         }
670       }
671       ierr = KSPSetUp(schurksp);CHKERRQ(ierr);
672     }
673   }
674   /* free */
675   ierr = ISDestroy(&is_I);CHKERRQ(ierr);
676   ierr = MatDestroy(&AE_II);CHKERRQ(ierr);
677   for (i=0;i<sub_schurs->n_subs;i++) {
678     ierr = MatDestroy(&AE_EE[i]);CHKERRQ(ierr);
679     ierr = MatDestroy(&AE_IE[i]);CHKERRQ(ierr);
680     ierr = MatDestroy(&AE_EI[i]);CHKERRQ(ierr);
681     ierr = ISDestroy(&is_subset_B[i]);CHKERRQ(ierr);
682   }
683   ierr = PetscFree4(is_subset_B,AE_IE,AE_EI,AE_EE);CHKERRQ(ierr);
684   PetscFunctionReturn(0);
685 }
686