xref: /petsc/src/mat/impls/aij/seq/matmatmult.c (revision d7ed1a4d02ac6f5303572c1c522caf4c249c9c19)
1 
2  /*
3    Defines matrix-matrix product routines for pairs of SeqAIJ matrices
4            C = A * B
5  */
6 
7  #include <../src/mat/impls/aij/seq/aij.h> /*I "petscmat.h" I*/
8  #include <../src/mat/utils/freespace.h>
9  #include <petscbt.h>
10  #include <petsc/private/isimpl.h>
11  #include <../src/mat/impls/dense/seq/dense.h>
12 
13  static PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_LLCondensed(Mat,Mat,PetscReal,Mat*);
14 
15  #if defined(PETSC_HAVE_HYPRE)
16  PETSC_INTERN PetscErrorCode MatMatMultSymbolic_AIJ_AIJ_wHYPRE(Mat,Mat,PetscReal,Mat*);
17  #endif
18 
19  PETSC_INTERN PetscErrorCode MatMatMult_SeqAIJ_SeqAIJ(Mat A,Mat B,MatReuse scall,PetscReal fill,Mat *C)
20  {
21    PetscErrorCode ierr;
22  #if !defined(PETSC_HAVE_HYPRE)
23    const char     *algTypes[8] = {"sorted","scalable","scalable_fast","heap","btheap","llcondensed","combined","rowmerge"};
24    PetscInt       nalg = 8;
25  #else
26    const char     *algTypes[9] = {"sorted","scalable","scalable_fast","heap","btheap","llcondensed","combined","rowmerge","hypre"};
27    PetscInt       nalg = 9;
28  #endif
29    PetscInt       alg = 0; /* set default algorithm */
30    PetscBool      combined = PETSC_FALSE;  /* Indicates whether the symbolic stage already computed the numerical values. */
31 
32    PetscFunctionBegin;
33    if (scall == MAT_INITIAL_MATRIX) {
34      ierr = PetscObjectOptionsBegin((PetscObject)A);CHKERRQ(ierr);
35      PetscOptionsObject->alreadyprinted = PETSC_FALSE; /* a hack to ensure the option shows in '-help' */
36      ierr = PetscOptionsEList("-matmatmult_via","Algorithmic approach","MatMatMult",algTypes,nalg,algTypes[0],&alg,NULL);CHKERRQ(ierr);
37      ierr = PetscOptionsEnd();CHKERRQ(ierr);
38      ierr = PetscLogEventBegin(MAT_MatMultSymbolic,A,B,0,0);CHKERRQ(ierr);
39      switch (alg) {
40      case 1:
41        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable(A,B,fill,C);CHKERRQ(ierr);
42        break;
43      case 2:
44        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable_fast(A,B,fill,C);CHKERRQ(ierr);
45        break;
46      case 3:
47        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_Heap(A,B,fill,C);CHKERRQ(ierr);
48        break;
49      case 4:
50        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_BTHeap(A,B,fill,C);CHKERRQ(ierr);
51        break;
52      case 5:
53        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_LLCondensed(A,B,fill,C);CHKERRQ(ierr);
54        break;
55      case 6:
56        ierr = MatMatMult_SeqAIJ_SeqAIJ_Combined(A,B,fill,C);CHKERRQ(ierr);
57        combined = PETSC_TRUE;
58        break;
59     case 7:
60        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ_RowMerge(A,B,fill,C);CHKERRQ(ierr);
61        break;
62  #if defined(PETSC_HAVE_HYPRE)
63      case 8:
64        ierr = MatMatMultSymbolic_AIJ_AIJ_wHYPRE(A,B,fill,C);CHKERRQ(ierr);
65        break;
66  #endif
67      default:
68        ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ(A,B,fill,C);CHKERRQ(ierr);
69       break;
70      }
71      ierr = PetscLogEventEnd(MAT_MatMultSymbolic,A,B,0,0);CHKERRQ(ierr);
72    }
73 
74    ierr = PetscLogEventBegin(MAT_MatMultNumeric,A,B,0,0);CHKERRQ(ierr);
75    if (!combined) {
76      ierr = (*(*C)->ops->matmultnumeric)(A,B,*C);CHKERRQ(ierr);
77    }
78    ierr = PetscLogEventEnd(MAT_MatMultNumeric,A,B,0,0);CHKERRQ(ierr);
79    PetscFunctionReturn(0);
80  }
81 
82  static PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_LLCondensed(Mat A,Mat B,PetscReal fill,Mat *C)
83  {
84    PetscErrorCode     ierr;
85    Mat_SeqAIJ         *a =(Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
86    PetscInt           *ai=a->i,*bi=b->i,*ci,*cj;
87    PetscInt           am =A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
88    PetscReal          afill;
89    PetscInt           i,j,anzi,brow,bnzj,cnzi,*bj,*aj,*lnk,ndouble=0,Crmax;
90    PetscTable         ta;
91    PetscBT            lnkbt;
92    PetscFreeSpaceList free_space=NULL,current_space=NULL;
93 
94    PetscFunctionBegin;
95    /* Get ci and cj */
96    /*---------------*/
97    /* Allocate ci array, arrays for fill computation and */
98    /* free space for accumulating nonzero column info */
99    ierr  = PetscMalloc1(am+2,&ci);CHKERRQ(ierr);
100    ci[0] = 0;
101 
102    /* create and initialize a linked list */
103    ierr = PetscTableCreate(bn,bn,&ta);CHKERRQ(ierr);
104    MatRowMergeMax_SeqAIJ(b,bm,ta);
105    ierr = PetscTableGetCount(ta,&Crmax);CHKERRQ(ierr);
106    ierr = PetscTableDestroy(&ta);CHKERRQ(ierr);
107 
108    ierr = PetscLLCondensedCreate(Crmax,bn,&lnk,&lnkbt);CHKERRQ(ierr);
109 
110    /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
111    ierr = PetscFreeSpaceGet(PetscRealIntMultTruncate(fill,PetscIntSumTruncate(ai[am],bi[bm])),&free_space);CHKERRQ(ierr);
112 
113    current_space = free_space;
114 
115    /* Determine ci and cj */
116    for (i=0; i<am; i++) {
117      anzi = ai[i+1] - ai[i];
118      aj   = a->j + ai[i];
119      for (j=0; j<anzi; j++) {
120        brow = aj[j];
121        bnzj = bi[brow+1] - bi[brow];
122        bj   = b->j + bi[brow];
123        /* add non-zero cols of B into the sorted linked list lnk */
124        ierr = PetscLLCondensedAddSorted(bnzj,bj,lnk,lnkbt);CHKERRQ(ierr);
125      }
126      cnzi = lnk[0];
127 
128      /* If free space is not available, make more free space */
129      /* Double the amount of total space in the list */
130      if (current_space->local_remaining<cnzi) {
131        ierr = PetscFreeSpaceGet(PetscIntSumTruncate(cnzi,current_space->total_array_size),&current_space);CHKERRQ(ierr);
132        ndouble++;
133      }
134 
135      /* Copy data into free space, then initialize lnk */
136      ierr = PetscLLCondensedClean(bn,cnzi,current_space->array,lnk,lnkbt);CHKERRQ(ierr);
137 
138      current_space->array           += cnzi;
139      current_space->local_used      += cnzi;
140      current_space->local_remaining -= cnzi;
141 
142      ci[i+1] = ci[i] + cnzi;
143    }
144 
145    /* Column indices are in the list of free space */
146    /* Allocate space for cj, initialize cj, and */
147    /* destroy list of free space and other temporary array(s) */
148    ierr = PetscMalloc1(ci[am]+1,&cj);CHKERRQ(ierr);
149    ierr = PetscFreeSpaceContiguous(&free_space,cj);CHKERRQ(ierr);
150    ierr = PetscLLCondensedDestroy(lnk,lnkbt);CHKERRQ(ierr);
151 
152    /* put together the new symbolic matrix */
153    ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
154    ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
155    ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
156 
157   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
158   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
159   c                         = (Mat_SeqAIJ*)((*C)->data);
160   c->free_a                 = PETSC_FALSE;
161   c->free_ij                = PETSC_TRUE;
162   c->nonew                  = 0;
163   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ; /* fast, needs non-scalable O(bn) array 'abdense' */
164 
165   /* set MatInfo */
166   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
167   if (afill < 1.0) afill = 1.0;
168   c->maxnz                     = ci[am];
169   c->nz                        = ci[am];
170   (*C)->info.mallocs           = ndouble;
171   (*C)->info.fill_ratio_given  = fill;
172   (*C)->info.fill_ratio_needed = afill;
173 
174 #if defined(PETSC_USE_INFO)
175   if (ci[am]) {
176     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
177     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
178   } else {
179     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
180   }
181 #endif
182   PetscFunctionReturn(0);
183 }
184 
185 PetscErrorCode MatMatMultNumeric_SeqAIJ_SeqAIJ(Mat A,Mat B,Mat C)
186 {
187   PetscErrorCode ierr;
188   PetscLogDouble flops=0.0;
189   Mat_SeqAIJ     *a   = (Mat_SeqAIJ*)A->data;
190   Mat_SeqAIJ     *b   = (Mat_SeqAIJ*)B->data;
191   Mat_SeqAIJ     *c   = (Mat_SeqAIJ*)C->data;
192   PetscInt       *ai  =a->i,*aj=a->j,*bi=b->i,*bj=b->j,*bjj,*ci=c->i,*cj=c->j;
193   PetscInt       am   =A->rmap->n,cm=C->rmap->n;
194   PetscInt       i,j,k,anzi,bnzi,cnzi,brow;
195   PetscScalar    *aa=a->a,*ba=b->a,*baj,*ca,valtmp;
196   PetscScalar    *ab_dense;
197 
198   PetscFunctionBegin;
199   if (!c->a) { /* first call of MatMatMultNumeric_SeqAIJ_SeqAIJ, allocate ca and matmult_abdense */
200     ierr      = PetscMalloc1(ci[cm]+1,&ca);CHKERRQ(ierr);
201     c->a      = ca;
202     c->free_a = PETSC_TRUE;
203   } else {
204     ca        = c->a;
205   }
206   if (!c->matmult_abdense) {
207     ierr = PetscCalloc1(B->cmap->N,&ab_dense);CHKERRQ(ierr);
208     c->matmult_abdense = ab_dense;
209   } else {
210     ab_dense = c->matmult_abdense;
211   }
212 
213   /* clean old values in C */
214   ierr = PetscMemzero(ca,ci[cm]*sizeof(MatScalar));CHKERRQ(ierr);
215   /* Traverse A row-wise. */
216   /* Build the ith row in C by summing over nonzero columns in A, */
217   /* the rows of B corresponding to nonzeros of A. */
218   for (i=0; i<am; i++) {
219     anzi = ai[i+1] - ai[i];
220     for (j=0; j<anzi; j++) {
221       brow = aj[j];
222       bnzi = bi[brow+1] - bi[brow];
223       bjj  = bj + bi[brow];
224       baj  = ba + bi[brow];
225       /* perform dense axpy */
226       valtmp = aa[j];
227       for (k=0; k<bnzi; k++) {
228         ab_dense[bjj[k]] += valtmp*baj[k];
229       }
230       flops += 2*bnzi;
231     }
232     aj += anzi; aa += anzi;
233 
234     cnzi = ci[i+1] - ci[i];
235     for (k=0; k<cnzi; k++) {
236       ca[k]          += ab_dense[cj[k]];
237       ab_dense[cj[k]] = 0.0; /* zero ab_dense */
238     }
239     flops += cnzi;
240     cj    += cnzi; ca += cnzi;
241   }
242   ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
243   ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
244   ierr = PetscLogFlops(flops);CHKERRQ(ierr);
245   PetscFunctionReturn(0);
246 }
247 
248 PetscErrorCode MatMatMultNumeric_SeqAIJ_SeqAIJ_Scalable(Mat A,Mat B,Mat C)
249 {
250   PetscErrorCode ierr;
251   PetscLogDouble flops=0.0;
252   Mat_SeqAIJ     *a   = (Mat_SeqAIJ*)A->data;
253   Mat_SeqAIJ     *b   = (Mat_SeqAIJ*)B->data;
254   Mat_SeqAIJ     *c   = (Mat_SeqAIJ*)C->data;
255   PetscInt       *ai  = a->i,*aj=a->j,*bi=b->i,*bj=b->j,*bjj,*ci=c->i,*cj=c->j;
256   PetscInt       am   = A->rmap->N,cm=C->rmap->N;
257   PetscInt       i,j,k,anzi,bnzi,cnzi,brow;
258   PetscScalar    *aa=a->a,*ba=b->a,*baj,*ca=c->a,valtmp;
259   PetscInt       nextb;
260 
261   PetscFunctionBegin;
262   if (!ca) { /* first call of MatMatMultNumeric_SeqAIJ_SeqAIJ, allocate ca and matmult_abdense */
263     ierr      = PetscMalloc1(ci[cm]+1,&ca);CHKERRQ(ierr);
264     c->a      = ca;
265     c->free_a = PETSC_TRUE;
266   }
267 
268   /* clean old values in C */
269   ierr = PetscMemzero(ca,ci[cm]*sizeof(MatScalar));CHKERRQ(ierr);
270   /* Traverse A row-wise. */
271   /* Build the ith row in C by summing over nonzero columns in A, */
272   /* the rows of B corresponding to nonzeros of A. */
273   for (i=0; i<am; i++) {
274     anzi = ai[i+1] - ai[i];
275     cnzi = ci[i+1] - ci[i];
276     for (j=0; j<anzi; j++) {
277       brow = aj[j];
278       bnzi = bi[brow+1] - bi[brow];
279       bjj  = bj + bi[brow];
280       baj  = ba + bi[brow];
281       /* perform sparse axpy */
282       valtmp = aa[j];
283       nextb  = 0;
284       for (k=0; nextb<bnzi; k++) {
285         if (cj[k] == bjj[nextb]) { /* ccol == bcol */
286           ca[k] += valtmp*baj[nextb++];
287         }
288       }
289       flops += 2*bnzi;
290     }
291     aj += anzi; aa += anzi;
292     cj += cnzi; ca += cnzi;
293   }
294 
295   ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
296   ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
297   ierr = PetscLogFlops(flops);CHKERRQ(ierr);
298   PetscFunctionReturn(0);
299 }
300 
301 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable_fast(Mat A,Mat B,PetscReal fill,Mat *C)
302 {
303   PetscErrorCode     ierr;
304   Mat_SeqAIJ         *a  = (Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
305   PetscInt           *ai = a->i,*bi=b->i,*ci,*cj;
306   PetscInt           am  = A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
307   MatScalar          *ca;
308   PetscReal          afill;
309   PetscInt           i,j,anzi,brow,bnzj,cnzi,*bj,*aj,*lnk,ndouble=0,Crmax;
310   PetscTable         ta;
311   PetscFreeSpaceList free_space=NULL,current_space=NULL;
312 
313   PetscFunctionBegin;
314   /* Get ci and cj - same as MatMatMultSymbolic_SeqAIJ_SeqAIJ except using PetscLLxxx_fast() */
315   /*-----------------------------------------------------------------------------------------*/
316   /* Allocate arrays for fill computation and free space for accumulating nonzero column */
317   ierr  = PetscMalloc1(am+2,&ci);CHKERRQ(ierr);
318   ci[0] = 0;
319 
320   /* create and initialize a linked list */
321   ierr = PetscTableCreate(bn,bn,&ta);CHKERRQ(ierr);
322   MatRowMergeMax_SeqAIJ(b,bm,ta);
323   ierr = PetscTableGetCount(ta,&Crmax);CHKERRQ(ierr);
324   ierr = PetscTableDestroy(&ta);CHKERRQ(ierr);
325 
326   ierr = PetscLLCondensedCreate_fast(Crmax,&lnk);CHKERRQ(ierr);
327 
328   /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
329   ierr          = PetscFreeSpaceGet(PetscRealIntMultTruncate(fill,PetscIntSumTruncate(ai[am],bi[bm])),&free_space);CHKERRQ(ierr);
330   current_space = free_space;
331 
332   /* Determine ci and cj */
333   for (i=0; i<am; i++) {
334     anzi = ai[i+1] - ai[i];
335     aj   = a->j + ai[i];
336     for (j=0; j<anzi; j++) {
337       brow = aj[j];
338       bnzj = bi[brow+1] - bi[brow];
339       bj   = b->j + bi[brow];
340       /* add non-zero cols of B into the sorted linked list lnk */
341       ierr = PetscLLCondensedAddSorted_fast(bnzj,bj,lnk);CHKERRQ(ierr);
342     }
343     cnzi = lnk[1];
344 
345     /* If free space is not available, make more free space */
346     /* Double the amount of total space in the list */
347     if (current_space->local_remaining<cnzi) {
348       ierr = PetscFreeSpaceGet(PetscIntSumTruncate(cnzi,current_space->total_array_size),&current_space);CHKERRQ(ierr);
349       ndouble++;
350     }
351 
352     /* Copy data into free space, then initialize lnk */
353     ierr = PetscLLCondensedClean_fast(cnzi,current_space->array,lnk);CHKERRQ(ierr);
354 
355     current_space->array           += cnzi;
356     current_space->local_used      += cnzi;
357     current_space->local_remaining -= cnzi;
358 
359     ci[i+1] = ci[i] + cnzi;
360   }
361 
362   /* Column indices are in the list of free space */
363   /* Allocate space for cj, initialize cj, and */
364   /* destroy list of free space and other temporary array(s) */
365   ierr = PetscMalloc1(ci[am]+1,&cj);CHKERRQ(ierr);
366   ierr = PetscFreeSpaceContiguous(&free_space,cj);CHKERRQ(ierr);
367   ierr = PetscLLCondensedDestroy_fast(lnk);CHKERRQ(ierr);
368 
369   /* Allocate space for ca */
370   ierr = PetscMalloc1(ci[am]+1,&ca);CHKERRQ(ierr);
371   ierr = PetscMemzero(ca,(ci[am]+1)*sizeof(MatScalar));CHKERRQ(ierr);
372 
373   /* put together the new symbolic matrix */
374   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,ca,C);CHKERRQ(ierr);
375   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
376   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
377 
378   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
379   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
380   c          = (Mat_SeqAIJ*)((*C)->data);
381   c->free_a  = PETSC_TRUE;
382   c->free_ij = PETSC_TRUE;
383   c->nonew   = 0;
384 
385   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ_Scalable; /* slower, less memory */
386 
387   /* set MatInfo */
388   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
389   if (afill < 1.0) afill = 1.0;
390   c->maxnz                     = ci[am];
391   c->nz                        = ci[am];
392   (*C)->info.mallocs           = ndouble;
393   (*C)->info.fill_ratio_given  = fill;
394   (*C)->info.fill_ratio_needed = afill;
395 
396 #if defined(PETSC_USE_INFO)
397   if (ci[am]) {
398     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
399     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
400   } else {
401     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
402   }
403 #endif
404   PetscFunctionReturn(0);
405 }
406 
407 
408 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable(Mat A,Mat B,PetscReal fill,Mat *C)
409 {
410   PetscErrorCode     ierr;
411   Mat_SeqAIJ         *a  = (Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
412   PetscInt           *ai = a->i,*bi=b->i,*ci,*cj;
413   PetscInt           am  = A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
414   MatScalar          *ca;
415   PetscReal          afill;
416   PetscInt           i,j,anzi,brow,bnzj,cnzi,*bj,*aj,*lnk,ndouble=0,Crmax;
417   PetscTable         ta;
418   PetscFreeSpaceList free_space=NULL,current_space=NULL;
419 
420   PetscFunctionBegin;
421   /* Get ci and cj - same as MatMatMultSymbolic_SeqAIJ_SeqAIJ except using PetscLLxxx_Scalalbe() */
422   /*---------------------------------------------------------------------------------------------*/
423   /* Allocate arrays for fill computation and free space for accumulating nonzero column */
424   ierr  = PetscMalloc1(am+2,&ci);CHKERRQ(ierr);
425   ci[0] = 0;
426 
427   /* create and initialize a linked list */
428   ierr = PetscTableCreate(bn,bn,&ta);CHKERRQ(ierr);
429   MatRowMergeMax_SeqAIJ(b,bm,ta);
430   ierr = PetscTableGetCount(ta,&Crmax);CHKERRQ(ierr);
431   ierr = PetscTableDestroy(&ta);CHKERRQ(ierr);
432   ierr = PetscLLCondensedCreate_Scalable(Crmax,&lnk);CHKERRQ(ierr);
433 
434   /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
435   ierr          = PetscFreeSpaceGet(PetscRealIntMultTruncate(fill,PetscIntSumTruncate(ai[am],bi[bm])),&free_space);CHKERRQ(ierr);
436   current_space = free_space;
437 
438   /* Determine ci and cj */
439   for (i=0; i<am; i++) {
440     anzi = ai[i+1] - ai[i];
441     aj   = a->j + ai[i];
442     for (j=0; j<anzi; j++) {
443       brow = aj[j];
444       bnzj = bi[brow+1] - bi[brow];
445       bj   = b->j + bi[brow];
446       /* add non-zero cols of B into the sorted linked list lnk */
447       ierr = PetscLLCondensedAddSorted_Scalable(bnzj,bj,lnk);CHKERRQ(ierr);
448     }
449     cnzi = lnk[0];
450 
451     /* If free space is not available, make more free space */
452     /* Double the amount of total space in the list */
453     if (current_space->local_remaining<cnzi) {
454       ierr = PetscFreeSpaceGet(PetscIntSumTruncate(cnzi,current_space->total_array_size),&current_space);CHKERRQ(ierr);
455       ndouble++;
456     }
457 
458     /* Copy data into free space, then initialize lnk */
459     ierr = PetscLLCondensedClean_Scalable(cnzi,current_space->array,lnk);CHKERRQ(ierr);
460 
461     current_space->array           += cnzi;
462     current_space->local_used      += cnzi;
463     current_space->local_remaining -= cnzi;
464 
465     ci[i+1] = ci[i] + cnzi;
466   }
467 
468   /* Column indices are in the list of free space */
469   /* Allocate space for cj, initialize cj, and */
470   /* destroy list of free space and other temporary array(s) */
471   ierr = PetscMalloc1(ci[am]+1,&cj);CHKERRQ(ierr);
472   ierr = PetscFreeSpaceContiguous(&free_space,cj);CHKERRQ(ierr);
473   ierr = PetscLLCondensedDestroy_Scalable(lnk);CHKERRQ(ierr);
474 
475   /* Allocate space for ca */
476   /*-----------------------*/
477   ierr = PetscMalloc1(ci[am]+1,&ca);CHKERRQ(ierr);
478   ierr = PetscMemzero(ca,(ci[am]+1)*sizeof(MatScalar));CHKERRQ(ierr);
479 
480   /* put together the new symbolic matrix */
481   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,ca,C);CHKERRQ(ierr);
482   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
483   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
484 
485   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
486   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
487   c          = (Mat_SeqAIJ*)((*C)->data);
488   c->free_a  = PETSC_TRUE;
489   c->free_ij = PETSC_TRUE;
490   c->nonew   = 0;
491 
492   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ_Scalable; /* slower, less memory */
493 
494   /* set MatInfo */
495   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
496   if (afill < 1.0) afill = 1.0;
497   c->maxnz                     = ci[am];
498   c->nz                        = ci[am];
499   (*C)->info.mallocs           = ndouble;
500   (*C)->info.fill_ratio_given  = fill;
501   (*C)->info.fill_ratio_needed = afill;
502 
503 #if defined(PETSC_USE_INFO)
504   if (ci[am]) {
505     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
506     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
507   } else {
508     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
509   }
510 #endif
511   PetscFunctionReturn(0);
512 }
513 
514 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_Heap(Mat A,Mat B,PetscReal fill,Mat *C)
515 {
516   PetscErrorCode     ierr;
517   Mat_SeqAIJ         *a = (Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
518   const PetscInt     *ai=a->i,*bi=b->i,*aj=a->j,*bj=b->j;
519   PetscInt           *ci,*cj,*bb;
520   PetscInt           am=A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
521   PetscReal          afill;
522   PetscInt           i,j,col,ndouble = 0;
523   PetscFreeSpaceList free_space=NULL,current_space=NULL;
524   PetscHeap          h;
525 
526   PetscFunctionBegin;
527   /* Get ci and cj - by merging sorted rows using a heap */
528   /*---------------------------------------------------------------------------------------------*/
529   /* Allocate arrays for fill computation and free space for accumulating nonzero column */
530   ierr  = PetscMalloc1(am+2,&ci);CHKERRQ(ierr);
531   ci[0] = 0;
532 
533   /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
534   ierr          = PetscFreeSpaceGet(PetscRealIntMultTruncate(fill,PetscIntSumTruncate(ai[am],bi[bm])),&free_space);CHKERRQ(ierr);
535   current_space = free_space;
536 
537   ierr = PetscHeapCreate(a->rmax,&h);CHKERRQ(ierr);
538   ierr = PetscMalloc1(a->rmax,&bb);CHKERRQ(ierr);
539 
540   /* Determine ci and cj */
541   for (i=0; i<am; i++) {
542     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
543     const PetscInt *acol = aj + ai[i]; /* column indices of nonzero entries in this row */
544     ci[i+1] = ci[i];
545     /* Populate the min heap */
546     for (j=0; j<anzi; j++) {
547       bb[j] = bi[acol[j]];         /* bb points at the start of the row */
548       if (bb[j] < bi[acol[j]+1]) { /* Add if row is nonempty */
549         ierr = PetscHeapAdd(h,j,bj[bb[j]++]);CHKERRQ(ierr);
550       }
551     }
552     /* Pick off the min element, adding it to free space */
553     ierr = PetscHeapPop(h,&j,&col);CHKERRQ(ierr);
554     while (j >= 0) {
555       if (current_space->local_remaining < 1) { /* double the size, but don't exceed 16 MiB */
556         ierr = PetscFreeSpaceGet(PetscMin(PetscIntMultTruncate(2,current_space->total_array_size),16 << 20),&current_space);CHKERRQ(ierr);
557         ndouble++;
558       }
559       *(current_space->array++) = col;
560       current_space->local_used++;
561       current_space->local_remaining--;
562       ci[i+1]++;
563 
564       /* stash if anything else remains in this row of B */
565       if (bb[j] < bi[acol[j]+1]) {ierr = PetscHeapStash(h,j,bj[bb[j]++]);CHKERRQ(ierr);}
566       while (1) {               /* pop and stash any other rows of B that also had an entry in this column */
567         PetscInt j2,col2;
568         ierr = PetscHeapPeek(h,&j2,&col2);CHKERRQ(ierr);
569         if (col2 != col) break;
570         ierr = PetscHeapPop(h,&j2,&col2);CHKERRQ(ierr);
571         if (bb[j2] < bi[acol[j2]+1]) {ierr = PetscHeapStash(h,j2,bj[bb[j2]++]);CHKERRQ(ierr);}
572       }
573       /* Put any stashed elements back into the min heap */
574       ierr = PetscHeapUnstash(h);CHKERRQ(ierr);
575       ierr = PetscHeapPop(h,&j,&col);CHKERRQ(ierr);
576     }
577   }
578   ierr = PetscFree(bb);CHKERRQ(ierr);
579   ierr = PetscHeapDestroy(&h);CHKERRQ(ierr);
580 
581   /* Column indices are in the list of free space */
582   /* Allocate space for cj, initialize cj, and */
583   /* destroy list of free space and other temporary array(s) */
584   ierr = PetscMalloc1(ci[am],&cj);CHKERRQ(ierr);
585   ierr = PetscFreeSpaceContiguous(&free_space,cj);CHKERRQ(ierr);
586 
587   /* put together the new symbolic matrix */
588   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
589   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
590   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
591 
592   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
593   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
594   c          = (Mat_SeqAIJ*)((*C)->data);
595   c->free_a  = PETSC_TRUE;
596   c->free_ij = PETSC_TRUE;
597   c->nonew   = 0;
598 
599   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ;
600 
601   /* set MatInfo */
602   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
603   if (afill < 1.0) afill = 1.0;
604   c->maxnz                     = ci[am];
605   c->nz                        = ci[am];
606   (*C)->info.mallocs           = ndouble;
607   (*C)->info.fill_ratio_given  = fill;
608   (*C)->info.fill_ratio_needed = afill;
609 
610 #if defined(PETSC_USE_INFO)
611   if (ci[am]) {
612     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
613     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
614   } else {
615     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
616   }
617 #endif
618   PetscFunctionReturn(0);
619 }
620 
621 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_BTHeap(Mat A,Mat B,PetscReal fill,Mat *C)
622 {
623   PetscErrorCode     ierr;
624   Mat_SeqAIJ         *a  = (Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
625   const PetscInt     *ai = a->i,*bi=b->i,*aj=a->j,*bj=b->j;
626   PetscInt           *ci,*cj,*bb;
627   PetscInt           am=A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
628   PetscReal          afill;
629   PetscInt           i,j,col,ndouble = 0;
630   PetscFreeSpaceList free_space=NULL,current_space=NULL;
631   PetscHeap          h;
632   PetscBT            bt;
633 
634   PetscFunctionBegin;
635   /* Get ci and cj - using a heap for the sorted rows, but use BT so that each index is only added once */
636   /*---------------------------------------------------------------------------------------------*/
637   /* Allocate arrays for fill computation and free space for accumulating nonzero column */
638   ierr  = PetscMalloc1(am+2,&ci);CHKERRQ(ierr);
639   ci[0] = 0;
640 
641   /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
642   ierr = PetscFreeSpaceGet(PetscRealIntMultTruncate(fill,PetscIntSumTruncate(ai[am],bi[bm])),&free_space);CHKERRQ(ierr);
643 
644   current_space = free_space;
645 
646   ierr = PetscHeapCreate(a->rmax,&h);CHKERRQ(ierr);
647   ierr = PetscMalloc1(a->rmax,&bb);CHKERRQ(ierr);
648   ierr = PetscBTCreate(bn,&bt);CHKERRQ(ierr);
649 
650   /* Determine ci and cj */
651   for (i=0; i<am; i++) {
652     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
653     const PetscInt *acol = aj + ai[i]; /* column indices of nonzero entries in this row */
654     const PetscInt *fptr = current_space->array; /* Save beginning of the row so we can clear the BT later */
655     ci[i+1] = ci[i];
656     /* Populate the min heap */
657     for (j=0; j<anzi; j++) {
658       PetscInt brow = acol[j];
659       for (bb[j] = bi[brow]; bb[j] < bi[brow+1]; bb[j]++) {
660         PetscInt bcol = bj[bb[j]];
661         if (!PetscBTLookupSet(bt,bcol)) { /* new entry */
662           ierr = PetscHeapAdd(h,j,bcol);CHKERRQ(ierr);
663           bb[j]++;
664           break;
665         }
666       }
667     }
668     /* Pick off the min element, adding it to free space */
669     ierr = PetscHeapPop(h,&j,&col);CHKERRQ(ierr);
670     while (j >= 0) {
671       if (current_space->local_remaining < 1) { /* double the size, but don't exceed 16 MiB */
672         fptr = NULL;                      /* need PetscBTMemzero */
673         ierr = PetscFreeSpaceGet(PetscMin(PetscIntMultTruncate(2,current_space->total_array_size),16 << 20),&current_space);CHKERRQ(ierr);
674         ndouble++;
675       }
676       *(current_space->array++) = col;
677       current_space->local_used++;
678       current_space->local_remaining--;
679       ci[i+1]++;
680 
681       /* stash if anything else remains in this row of B */
682       for (; bb[j] < bi[acol[j]+1]; bb[j]++) {
683         PetscInt bcol = bj[bb[j]];
684         if (!PetscBTLookupSet(bt,bcol)) { /* new entry */
685           ierr = PetscHeapAdd(h,j,bcol);CHKERRQ(ierr);
686           bb[j]++;
687           break;
688         }
689       }
690       ierr = PetscHeapPop(h,&j,&col);CHKERRQ(ierr);
691     }
692     if (fptr) {                 /* Clear the bits for this row */
693       for (; fptr<current_space->array; fptr++) {ierr = PetscBTClear(bt,*fptr);CHKERRQ(ierr);}
694     } else {                    /* We reallocated so we don't remember (easily) how to clear only the bits we changed */
695       ierr = PetscBTMemzero(bn,bt);CHKERRQ(ierr);
696     }
697   }
698   ierr = PetscFree(bb);CHKERRQ(ierr);
699   ierr = PetscHeapDestroy(&h);CHKERRQ(ierr);
700   ierr = PetscBTDestroy(&bt);CHKERRQ(ierr);
701 
702   /* Column indices are in the list of free space */
703   /* Allocate space for cj, initialize cj, and */
704   /* destroy list of free space and other temporary array(s) */
705   ierr = PetscMalloc1(ci[am],&cj);CHKERRQ(ierr);
706   ierr = PetscFreeSpaceContiguous(&free_space,cj);CHKERRQ(ierr);
707 
708   /* put together the new symbolic matrix */
709   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
710   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
711   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
712 
713   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
714   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
715   c          = (Mat_SeqAIJ*)((*C)->data);
716   c->free_a  = PETSC_TRUE;
717   c->free_ij = PETSC_TRUE;
718   c->nonew   = 0;
719 
720   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ;
721 
722   /* set MatInfo */
723   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
724   if (afill < 1.0) afill = 1.0;
725   c->maxnz                     = ci[am];
726   c->nz                        = ci[am];
727   (*C)->info.mallocs           = ndouble;
728   (*C)->info.fill_ratio_given  = fill;
729   (*C)->info.fill_ratio_needed = afill;
730 
731 #if defined(PETSC_USE_INFO)
732   if (ci[am]) {
733     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
734     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
735   } else {
736     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
737   }
738 #endif
739   PetscFunctionReturn(0);
740 }
741 
742 
743 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ_RowMerge(Mat A,Mat B,PetscReal fill,Mat *C)
744 {
745   PetscErrorCode     ierr;
746   Mat_SeqAIJ         *a=(Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
747   const PetscInt     *ai=a->i,*bi=b->i,*aj=a->j,*bj=b->j,*inputi,*inputj,*inputcol,*inputcol_L1;
748   PetscInt           *ci,*cj,*outputj,worki_L1[9],worki_L2[9];
749   PetscInt           c_maxmem,a_maxrownnz=0,a_rownnz;
750   const PetscInt     workcol[8] = {0,1,2,3,4,5,6,7};
751   const PetscInt     am=A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
752   const PetscInt     *brow_ptr[8],*brow_end[8];
753   PetscInt           window[8];
754   PetscInt           window_min,old_window_min,ci_nnz,outputi_nnz=0,L1_nrows,L2_nrows;
755   PetscInt           i,k,ndouble = 0,L1_rowsleft,rowsleft;
756   PetscReal          afill;
757   PetscInt           *workj_L1,*workj_L2,*workj_L3_in,*workj_L3_out;
758   PetscInt           L2_nnz,L3_nnz;
759   PetscBool          merge_from_2_arrays = PETSC_FALSE;
760 
761   /* Step 1: Get upper bound on memory required for allocation.
762              Because of the way virtual memory works,
763              only the memory pages that are actually needed will be physically allocated. */
764   PetscFunctionBegin;
765   ierr  = PetscMalloc1(am+1,&ci);CHKERRQ(ierr);
766 
767   for (i=0; i<am; i++) {
768     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
769     const PetscInt *acol = aj + ai[i]; /* column indices of nonzero entries in this row */
770     a_rownnz = 0;
771     for (k=0; k<anzi; ++k) {
772       a_rownnz += bi[acol[k]+1] - bi[acol[k]];
773       if (a_rownnz > bn) {
774         a_rownnz = bn;
775         break;
776       }
777     }
778     a_maxrownnz = PetscMax(a_maxrownnz, a_rownnz);
779   }
780   /* This should be enough for almost all matrices. If not, memory is reallocated later. */
781   c_maxmem = 4*(ai[am]+bi[bm]);
782 
783   /* temporary work areas for merging rows */
784   ierr = PetscMalloc1(a_maxrownnz*8,&workj_L1);CHKERRQ(ierr);
785   ierr = PetscMalloc1(a_maxrownnz*8,&workj_L2);CHKERRQ(ierr);
786   ierr = PetscMalloc1(a_maxrownnz,&workj_L3_in);CHKERRQ(ierr);
787   ierr = PetscMalloc1(a_maxrownnz,&workj_L3_out);CHKERRQ(ierr);
788 
789   /* Step 2: Populate pattern for C */
790   ierr  = PetscMalloc1(c_maxmem,&cj);CHKERRQ(ierr);
791 
792   ci_nnz       = 0;
793   ci[0]        = 0;
794   worki_L1[0]  = 0;
795   worki_L2[0]  = 0;
796   worki_L2[1]  = 0;
797   for (i=0; i<am; i++) {
798     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
799     const PetscInt *acol = aj + ai[i];      /* column indices of nonzero entries in this row */
800     rowsleft             = anzi;
801     inputcol_L1          = acol;
802     L2_nnz               = 0;
803     L2_nrows             = 1;  /* Number of rows to be merged on Level 3. workj_L3_in already exists -> initial value 1   */
804     L3_nnz               = 0;
805 
806     /* If the number of indices in C so far + the max number of columns in the next row > c_maxmem  -> allocate more memory */
807     while (ci_nnz+a_maxrownnz > c_maxmem) {
808       c_maxmem *= 2;
809       ndouble++;
810       ierr = PetscRealloc(sizeof(PetscInt)*c_maxmem,&cj);CHKERRQ(ierr);
811     }
812 
813     while (rowsleft) {
814       L1_rowsleft = PetscMin(64, rowsleft); /* In the inner loop max 64 rows of B can be merged */
815       L1_nrows    = 0;
816       outputi_nnz = 0;
817       inputcol    = inputcol_L1;
818       inputi      = bi;
819       inputj      = bj;
820 
821       if (anzi > 8)  outputj = workj_L1;     /* Level 1 rowmerge*/
822       else           outputj = cj + ci_nnz; /* Merge directly to C */
823 
824       /* The following macro is used to specialize for small rows in A.
825          This helps with compiler unrolling, improving performance substantially.
826           Input:  inputj   inputi  workj_L3_in  L3_nnz inputcol  bn
827           Output: outputj  outputi_nnz                       */
828        #define MatMatMultSymbolic_RowMergeMacro(ANNZ)      \
829          window_min  = bn;                                 \
830          if (merge_from_2_arrays) {                        \
831            brow_ptr[0] = workj_L3_in;                      \
832            brow_end[0] = workj_L3_in + L3_nnz;             \
833          } else {                                          \
834            brow_ptr[0] = inputj + inputi[inputcol[0]];     \
835            brow_end[0] = inputj + inputi[inputcol[0]+1];   \
836          }                                                 \
837          for (k=1; k<ANNZ; ++k) {                          \
838            brow_ptr[k] = inputj + inputi[inputcol[k]];     \
839            brow_end[k] = inputj + inputi[inputcol[k]+1];   \
840          }                                                 \
841          for (k=0; k<ANNZ; ++k) {                          \
842            window[k] = (brow_ptr[k] != brow_end[k]) ? *brow_ptr[k] : bn; \
843            window_min = PetscMin(window[k], window_min);   \
844          }                                                 \
845          while (window_min < bn) {                         \
846            outputj[outputi_nnz++] = window_min;            \
847            /* advance front and compute new minimum */     \
848            old_window_min = window_min;                    \
849            window_min = bn;                                \
850            for (k=0; k<ANNZ; ++k) {                        \
851              if (window[k] == old_window_min) {            \
852                brow_ptr[k]++;                              \
853                window[k] = (brow_ptr[k] != brow_end[k]) ? *brow_ptr[k] : bn; \
854              }                                             \
855              window_min = PetscMin(window[k], window_min); \
856            }                                               \
857          }
858 
859       /************** L E V E L  1 ***************/
860       /* Merge up to 8 rows of B to L1 work array*/
861       while (L1_rowsleft) {
862         switch (L1_rowsleft) {
863         case 1:  brow_ptr[0] = inputj + inputi[inputcol[0]];
864                  brow_end[0] = inputj + inputi[inputcol[0]+1];
865                  for (; brow_ptr[0] != brow_end[0]; ++brow_ptr[0]) outputj[outputi_nnz++] = *brow_ptr[0]; /* copy row in b over */
866                  inputcol    += L1_rowsleft;
867                  rowsleft    -= L1_rowsleft;
868                  L1_rowsleft  = 0;
869                  break;
870         case 2:  MatMatMultSymbolic_RowMergeMacro(2);
871                  inputcol    += L1_rowsleft;
872                  rowsleft    -= L1_rowsleft;
873                  L1_rowsleft  = 0;
874                  break;
875         case 3: MatMatMultSymbolic_RowMergeMacro(3);
876                  inputcol    += L1_rowsleft;
877                  rowsleft    -= L1_rowsleft;
878                  L1_rowsleft  = 0;
879                  break;
880         case 4:  MatMatMultSymbolic_RowMergeMacro(4);
881                  inputcol    += L1_rowsleft;
882                  rowsleft    -= L1_rowsleft;
883                  L1_rowsleft  = 0;
884                  break;
885         case 5:  MatMatMultSymbolic_RowMergeMacro(5);
886                  inputcol    += L1_rowsleft;
887                  rowsleft    -= L1_rowsleft;
888                  L1_rowsleft  = 0;
889                  break;
890         case 6:  MatMatMultSymbolic_RowMergeMacro(6);
891                  inputcol    += L1_rowsleft;
892                  rowsleft    -= L1_rowsleft;
893                  L1_rowsleft  = 0;
894                  break;
895         case 7:  MatMatMultSymbolic_RowMergeMacro(7);
896                  inputcol    += L1_rowsleft;
897                  rowsleft    -= L1_rowsleft;
898                  L1_rowsleft  = 0;
899                  break;
900         default: MatMatMultSymbolic_RowMergeMacro(8);
901                  inputcol    += 8;
902                  rowsleft    -= 8;
903                  L1_rowsleft -= 8;
904                  break;
905         }
906         inputcol_L1 = inputcol;
907         if (anzi > 8) worki_L1[++L1_nrows] = outputi_nnz;
908       }
909 
910       /********************** L E V E L  2 ************************/
911       /* Merge from L1 work array to either C or to L2 work array */
912       if (anzi > 8) {
913         inputi      = worki_L1;
914         inputj      = workj_L1;
915         inputcol    = workcol;
916         outputi_nnz = 0;
917 
918         if (anzi <= 64) outputj = cj + ci_nnz;        /* Merge from L1 work array to C */
919         else            outputj = workj_L2 + L2_nnz;  /* Merge from L1 work array to L2 work array */
920 
921         switch (L1_nrows) {
922         case 1:  brow_ptr[0] = inputj + inputi[inputcol[0]];
923                  brow_end[0] = inputj + inputi[inputcol[0]+1];
924                  for (; brow_ptr[0] != brow_end[0]; ++brow_ptr[0]) outputj[outputi_nnz++] = *brow_ptr[0]; /* copy row in b over */
925                  break;
926         case 2:  MatMatMultSymbolic_RowMergeMacro(2); break;
927         case 3:  MatMatMultSymbolic_RowMergeMacro(3); break;
928         case 4:  MatMatMultSymbolic_RowMergeMacro(4); break;
929         case 5:  MatMatMultSymbolic_RowMergeMacro(5); break;
930         case 6:  MatMatMultSymbolic_RowMergeMacro(6); break;
931         case 7:  MatMatMultSymbolic_RowMergeMacro(7); break;
932         case 8:  MatMatMultSymbolic_RowMergeMacro(8); break;
933         default: SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"MatMatMult logic error: Not merging 1-8 rows from L1 work array!");
934         }
935         L2_nnz               += outputi_nnz;
936         worki_L2[++L2_nrows]  = L2_nnz;
937 
938         /******************************* L E V E L  3 *******************************/
939         /* Merge from L2 work array and workj_L3_in to either C or to L3 work array */
940         if (anzi > 64 && (L2_nrows == 8 || rowsleft == 0)) {
941           inputi      = worki_L2;
942           inputj      = workj_L2;
943           inputcol    = workcol;
944           outputi_nnz = 0;
945           if (rowsleft) outputj = workj_L3_out;
946           else          outputj = cj + ci_nnz;
947           merge_from_2_arrays = PETSC_TRUE;  /* Instead of merging only from the array inputj, workj_L3_in is also used now. */
948           switch (L2_nrows) {
949           case 1:  brow_ptr[0] = inputj + inputi[inputcol[0]];
950                    brow_end[0] = inputj + inputi[inputcol[0]+1];
951                    for (; brow_ptr[0] != brow_end[0]; ++brow_ptr[0]) outputj[outputi_nnz++] = *brow_ptr[0]; /* copy row in b over */
952                    break;
953           case 2:  MatMatMultSymbolic_RowMergeMacro(2); break;
954           case 3:  MatMatMultSymbolic_RowMergeMacro(3); break;
955           case 4:  MatMatMultSymbolic_RowMergeMacro(4); break;
956           case 5:  MatMatMultSymbolic_RowMergeMacro(5); break;
957           case 6:  MatMatMultSymbolic_RowMergeMacro(6); break;
958           case 7:  MatMatMultSymbolic_RowMergeMacro(7); break;
959           case 8:  MatMatMultSymbolic_RowMergeMacro(8); break;
960           default: SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"MatMatMult logic error: Not merging 1-8 rows from L2 work array!");
961           }
962           merge_from_2_arrays = PETSC_FALSE;
963           L2_nrows            = 1;
964           L2_nnz              = 0;
965           L3_nnz              = outputi_nnz;
966           /* Copy to workj_L3_in */
967           if (rowsleft) {
968             for (k=0; k<outputi_nnz; ++k)  workj_L3_in[k] = outputj[k];
969           }
970         }
971       }
972     }  /* while (rowsleft) */
973 #undef MatMatMultSymbolic_RowMergeMacro
974 
975     /* terminate current row */
976     ci_nnz += outputi_nnz;
977     ci[i+1] = ci_nnz;
978   }
979 
980   /* Step 3: Create the new symbolic matrix */
981   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
982   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
983 
984   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
985   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
986   c          = (Mat_SeqAIJ*)((*C)->data);
987   c->free_a  = PETSC_TRUE;
988   c->free_ij = PETSC_TRUE;
989   c->nonew   = 0;
990 
991   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ;
992 
993   /* set MatInfo */
994   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
995   if (afill < 1.0) afill = 1.0;
996   c->maxnz                     = ci[am];
997   c->nz                        = ci[am];
998   (*C)->info.mallocs           = ndouble;
999   (*C)->info.fill_ratio_given  = fill;
1000   (*C)->info.fill_ratio_needed = afill;
1001 
1002 #if defined(PETSC_USE_INFO)
1003   if (ci[am]) {
1004     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
1005     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
1006   } else {
1007     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
1008   }
1009 #endif
1010 
1011   /* Step 4: Free temporary work areas */
1012   ierr = PetscFree(workj_L1);CHKERRQ(ierr);
1013   ierr = PetscFree(workj_L2);CHKERRQ(ierr);
1014   ierr = PetscFree(workj_L3_in);CHKERRQ(ierr);
1015   ierr = PetscFree(workj_L3_out);CHKERRQ(ierr);
1016   PetscFunctionReturn(0);
1017 }
1018 
1019 /* concatenate unique entries and then sort */
1020 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqAIJ(Mat A,Mat B,PetscReal fill,Mat *C)
1021 {
1022   PetscErrorCode     ierr;
1023   Mat_SeqAIJ         *a  = (Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c;
1024   const PetscInt     *ai = a->i,*bi=b->i,*aj=a->j,*bj=b->j;
1025   PetscInt           *ci,*cj;
1026   PetscInt           am=A->rmap->N,bn=B->cmap->N,bm=B->rmap->N;
1027   PetscReal          afill;
1028   PetscInt           i,j,ndouble = 0;
1029   PetscSegBuffer     seg,segrow;
1030   char               *seen;
1031 
1032   PetscFunctionBegin;
1033   ierr  = PetscMalloc1(am+1,&ci);CHKERRQ(ierr);
1034   ci[0] = 0;
1035 
1036   /* Initial FreeSpace size is fill*(nnz(A)+nnz(B)) */
1037   ierr = PetscSegBufferCreate(sizeof(PetscInt),(PetscInt)(fill*(ai[am]+bi[bm])),&seg);CHKERRQ(ierr);
1038   ierr = PetscSegBufferCreate(sizeof(PetscInt),100,&segrow);CHKERRQ(ierr);
1039   ierr = PetscMalloc1(bn,&seen);CHKERRQ(ierr);
1040   ierr = PetscMemzero(seen,bn*sizeof(char));CHKERRQ(ierr);
1041 
1042   /* Determine ci and cj */
1043   for (i=0; i<am; i++) {
1044     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
1045     const PetscInt *acol = aj + ai[i]; /* column indices of nonzero entries in this row */
1046     PetscInt packlen = 0,*PETSC_RESTRICT crow;
1047     /* Pack segrow */
1048     for (j=0; j<anzi; j++) {
1049       PetscInt brow = acol[j],bjstart = bi[brow],bjend = bi[brow+1],k;
1050       for (k=bjstart; k<bjend; k++) {
1051         PetscInt bcol = bj[k];
1052         if (!seen[bcol]) { /* new entry */
1053           PetscInt *PETSC_RESTRICT slot;
1054           ierr = PetscSegBufferGetInts(segrow,1,&slot);CHKERRQ(ierr);
1055           *slot = bcol;
1056           seen[bcol] = 1;
1057           packlen++;
1058         }
1059       }
1060     }
1061     ierr = PetscSegBufferGetInts(seg,packlen,&crow);CHKERRQ(ierr);
1062     ierr = PetscSegBufferExtractTo(segrow,crow);CHKERRQ(ierr);
1063     ierr = PetscSortInt(packlen,crow);CHKERRQ(ierr);
1064     ci[i+1] = ci[i] + packlen;
1065     for (j=0; j<packlen; j++) seen[crow[j]] = 0;
1066   }
1067   ierr = PetscSegBufferDestroy(&segrow);CHKERRQ(ierr);
1068   ierr = PetscFree(seen);CHKERRQ(ierr);
1069 
1070   /* Column indices are in the segmented buffer */
1071   ierr = PetscSegBufferExtractAlloc(seg,&cj);CHKERRQ(ierr);
1072   ierr = PetscSegBufferDestroy(&seg);CHKERRQ(ierr);
1073 
1074   /* put together the new symbolic matrix */
1075   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
1076   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
1077   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
1078 
1079   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
1080   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
1081   c          = (Mat_SeqAIJ*)((*C)->data);
1082   c->free_a  = PETSC_TRUE;
1083   c->free_ij = PETSC_TRUE;
1084   c->nonew   = 0;
1085 
1086   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqAIJ;
1087 
1088   /* set MatInfo */
1089   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
1090   if (afill < 1.0) afill = 1.0;
1091   c->maxnz                     = ci[am];
1092   c->nz                        = ci[am];
1093   (*C)->info.mallocs           = ndouble;
1094   (*C)->info.fill_ratio_given  = fill;
1095   (*C)->info.fill_ratio_needed = afill;
1096 
1097 #if defined(PETSC_USE_INFO)
1098   if (ci[am]) {
1099     ierr = PetscInfo3((*C),"Reallocs %D; Fill ratio: given %g needed %g.\n",ndouble,(double)fill,(double)afill);CHKERRQ(ierr);
1100     ierr = PetscInfo1((*C),"Use MatMatMult(A,B,MatReuse,%g,&C) for best performance.;\n",(double)afill);CHKERRQ(ierr);
1101   } else {
1102     ierr = PetscInfo((*C),"Empty matrix product\n");CHKERRQ(ierr);
1103   }
1104 #endif
1105   PetscFunctionReturn(0);
1106 }
1107 
1108 /* This routine is not used. Should be removed! */
1109 PetscErrorCode MatMatTransposeMult_SeqAIJ_SeqAIJ(Mat A,Mat B,MatReuse scall,PetscReal fill,Mat *C)
1110 {
1111   PetscErrorCode ierr;
1112 
1113   PetscFunctionBegin;
1114   if (scall == MAT_INITIAL_MATRIX) {
1115     ierr = PetscLogEventBegin(MAT_MatTransposeMultSymbolic,A,B,0,0);CHKERRQ(ierr);
1116     ierr = MatMatTransposeMultSymbolic_SeqAIJ_SeqAIJ(A,B,fill,C);CHKERRQ(ierr);
1117     ierr = PetscLogEventEnd(MAT_MatTransposeMultSymbolic,A,B,0,0);CHKERRQ(ierr);
1118   }
1119   ierr = PetscLogEventBegin(MAT_MatTransposeMultNumeric,A,B,0,0);CHKERRQ(ierr);
1120   ierr = MatMatTransposeMultNumeric_SeqAIJ_SeqAIJ(A,B,*C);CHKERRQ(ierr);
1121   ierr = PetscLogEventEnd(MAT_MatTransposeMultNumeric,A,B,0,0);CHKERRQ(ierr);
1122   PetscFunctionReturn(0);
1123 }
1124 
1125 PetscErrorCode MatDestroy_SeqAIJ_MatMatMultTrans(Mat A)
1126 {
1127   PetscErrorCode      ierr;
1128   Mat_SeqAIJ          *a=(Mat_SeqAIJ*)A->data;
1129   Mat_MatMatTransMult *abt=a->abt;
1130 
1131   PetscFunctionBegin;
1132   ierr = (abt->destroy)(A);CHKERRQ(ierr);
1133   ierr = MatTransposeColoringDestroy(&abt->matcoloring);CHKERRQ(ierr);
1134   ierr = MatDestroy(&abt->Bt_den);CHKERRQ(ierr);
1135   ierr = MatDestroy(&abt->ABt_den);CHKERRQ(ierr);
1136   ierr = PetscFree(abt);CHKERRQ(ierr);
1137   PetscFunctionReturn(0);
1138 }
1139 
1140 PetscErrorCode MatMatTransposeMultSymbolic_SeqAIJ_SeqAIJ(Mat A,Mat B,PetscReal fill,Mat *C)
1141 {
1142   PetscErrorCode      ierr;
1143   Mat                 Bt;
1144   PetscInt            *bti,*btj;
1145   Mat_MatMatTransMult *abt;
1146   Mat_SeqAIJ          *c;
1147 
1148   PetscFunctionBegin;
1149   /* create symbolic Bt */
1150   ierr = MatGetSymbolicTranspose_SeqAIJ(B,&bti,&btj);CHKERRQ(ierr);
1151   ierr = MatCreateSeqAIJWithArrays(PETSC_COMM_SELF,B->cmap->n,B->rmap->n,bti,btj,NULL,&Bt);CHKERRQ(ierr);
1152   ierr = MatSetBlockSizes(Bt,PetscAbs(A->cmap->bs),PetscAbs(B->cmap->bs));CHKERRQ(ierr);
1153   ierr = MatSetType(Bt,((PetscObject)A)->type_name);CHKERRQ(ierr);
1154 
1155   /* get symbolic C=A*Bt */
1156   ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ(A,Bt,fill,C);CHKERRQ(ierr);
1157 
1158   /* create a supporting struct for reuse intermidiate dense matrices with matcoloring */
1159   ierr   = PetscNew(&abt);CHKERRQ(ierr);
1160   c      = (Mat_SeqAIJ*)(*C)->data;
1161   c->abt = abt;
1162 
1163   abt->usecoloring = PETSC_FALSE;
1164   abt->destroy     = (*C)->ops->destroy;
1165   (*C)->ops->destroy     = MatDestroy_SeqAIJ_MatMatMultTrans;
1166 
1167   ierr = PetscOptionsGetBool(((PetscObject)A)->options,NULL,"-matmattransmult_color",&abt->usecoloring,NULL);CHKERRQ(ierr);
1168   if (abt->usecoloring) {
1169     /* Create MatTransposeColoring from symbolic C=A*B^T */
1170     MatTransposeColoring matcoloring;
1171     MatColoring          coloring;
1172     ISColoring           iscoloring;
1173     Mat                  Bt_dense,C_dense;
1174     Mat_SeqAIJ           *c=(Mat_SeqAIJ*)(*C)->data;
1175     /* inode causes memory problem, don't know why */
1176     if (c->inode.use) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"MAT_USE_INODES is not supported. Use '-mat_no_inode'");
1177 
1178     ierr = MatColoringCreate(*C,&coloring);CHKERRQ(ierr);
1179     ierr = MatColoringSetDistance(coloring,2);CHKERRQ(ierr);
1180     ierr = MatColoringSetType(coloring,MATCOLORINGSL);CHKERRQ(ierr);
1181     ierr = MatColoringSetFromOptions(coloring);CHKERRQ(ierr);
1182     ierr = MatColoringApply(coloring,&iscoloring);CHKERRQ(ierr);
1183     ierr = MatColoringDestroy(&coloring);CHKERRQ(ierr);
1184     ierr = MatTransposeColoringCreate(*C,iscoloring,&matcoloring);CHKERRQ(ierr);
1185 
1186     abt->matcoloring = matcoloring;
1187 
1188     ierr = ISColoringDestroy(&iscoloring);CHKERRQ(ierr);
1189 
1190     /* Create Bt_dense and C_dense = A*Bt_dense */
1191     ierr = MatCreate(PETSC_COMM_SELF,&Bt_dense);CHKERRQ(ierr);
1192     ierr = MatSetSizes(Bt_dense,A->cmap->n,matcoloring->ncolors,A->cmap->n,matcoloring->ncolors);CHKERRQ(ierr);
1193     ierr = MatSetType(Bt_dense,MATSEQDENSE);CHKERRQ(ierr);
1194     ierr = MatSeqDenseSetPreallocation(Bt_dense,NULL);CHKERRQ(ierr);
1195 
1196     Bt_dense->assembled = PETSC_TRUE;
1197     abt->Bt_den   = Bt_dense;
1198 
1199     ierr = MatCreate(PETSC_COMM_SELF,&C_dense);CHKERRQ(ierr);
1200     ierr = MatSetSizes(C_dense,A->rmap->n,matcoloring->ncolors,A->rmap->n,matcoloring->ncolors);CHKERRQ(ierr);
1201     ierr = MatSetType(C_dense,MATSEQDENSE);CHKERRQ(ierr);
1202     ierr = MatSeqDenseSetPreallocation(C_dense,NULL);CHKERRQ(ierr);
1203 
1204     Bt_dense->assembled = PETSC_TRUE;
1205     abt->ABt_den  = C_dense;
1206 
1207 #if defined(PETSC_USE_INFO)
1208     {
1209       Mat_SeqAIJ *c = (Mat_SeqAIJ*)(*C)->data;
1210       ierr = PetscInfo7(*C,"Use coloring of C=A*B^T; B^T: %D %D, Bt_dense: %D,%D; Cnz %D / (cm*ncolors %D) = %g\n",B->cmap->n,B->rmap->n,Bt_dense->rmap->n,Bt_dense->cmap->n,c->nz,A->rmap->n*matcoloring->ncolors,(PetscReal)(c->nz)/(A->rmap->n*matcoloring->ncolors));CHKERRQ(ierr);
1211     }
1212 #endif
1213   }
1214   /* clean up */
1215   ierr = MatDestroy(&Bt);CHKERRQ(ierr);
1216   ierr = MatRestoreSymbolicTranspose_SeqAIJ(B,&bti,&btj);CHKERRQ(ierr);
1217   PetscFunctionReturn(0);
1218 }
1219 
1220 PetscErrorCode MatMatTransposeMultNumeric_SeqAIJ_SeqAIJ(Mat A,Mat B,Mat C)
1221 {
1222   PetscErrorCode      ierr;
1223   Mat_SeqAIJ          *a   =(Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c=(Mat_SeqAIJ*)C->data;
1224   PetscInt            *ai  =a->i,*aj=a->j,*bi=b->i,*bj=b->j,anzi,bnzj,nexta,nextb,*acol,*bcol,brow;
1225   PetscInt            cm   =C->rmap->n,*ci=c->i,*cj=c->j,i,j,cnzi,*ccol;
1226   PetscLogDouble      flops=0.0;
1227   MatScalar           *aa  =a->a,*aval,*ba=b->a,*bval,*ca,*cval;
1228   Mat_MatMatTransMult *abt = c->abt;
1229 
1230   PetscFunctionBegin;
1231   /* clear old values in C */
1232   if (!c->a) {
1233     ierr      = PetscMalloc1(ci[cm]+1,&ca);CHKERRQ(ierr);
1234     c->a      = ca;
1235     c->free_a = PETSC_TRUE;
1236   } else {
1237     ca =  c->a;
1238   }
1239   ierr = PetscMemzero(ca,ci[cm]*sizeof(MatScalar));CHKERRQ(ierr);
1240 
1241   if (abt->usecoloring) {
1242     MatTransposeColoring matcoloring = abt->matcoloring;
1243     Mat                  Bt_dense,C_dense = abt->ABt_den;
1244 
1245     /* Get Bt_dense by Apply MatTransposeColoring to B */
1246     Bt_dense = abt->Bt_den;
1247     ierr = MatTransColoringApplySpToDen(matcoloring,B,Bt_dense);CHKERRQ(ierr);
1248 
1249     /* C_dense = A*Bt_dense */
1250     ierr = MatMatMultNumeric_SeqAIJ_SeqDense(A,Bt_dense,C_dense);CHKERRQ(ierr);
1251 
1252     /* Recover C from C_dense */
1253     ierr = MatTransColoringApplyDenToSp(matcoloring,C_dense,C);CHKERRQ(ierr);
1254     PetscFunctionReturn(0);
1255   }
1256 
1257   for (i=0; i<cm; i++) {
1258     anzi = ai[i+1] - ai[i];
1259     acol = aj + ai[i];
1260     aval = aa + ai[i];
1261     cnzi = ci[i+1] - ci[i];
1262     ccol = cj + ci[i];
1263     cval = ca + ci[i];
1264     for (j=0; j<cnzi; j++) {
1265       brow = ccol[j];
1266       bnzj = bi[brow+1] - bi[brow];
1267       bcol = bj + bi[brow];
1268       bval = ba + bi[brow];
1269 
1270       /* perform sparse inner-product c(i,j)=A[i,:]*B[j,:]^T */
1271       nexta = 0; nextb = 0;
1272       while (nexta<anzi && nextb<bnzj) {
1273         while (nexta < anzi && acol[nexta] < bcol[nextb]) nexta++;
1274         if (nexta == anzi) break;
1275         while (nextb < bnzj && acol[nexta] > bcol[nextb]) nextb++;
1276         if (nextb == bnzj) break;
1277         if (acol[nexta] == bcol[nextb]) {
1278           cval[j] += aval[nexta]*bval[nextb];
1279           nexta++; nextb++;
1280           flops += 2;
1281         }
1282       }
1283     }
1284   }
1285   ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1286   ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1287   ierr = PetscLogFlops(flops);CHKERRQ(ierr);
1288   PetscFunctionReturn(0);
1289 }
1290 
1291 PetscErrorCode MatDestroy_SeqAIJ_MatTransMatMult(Mat A)
1292 {
1293   PetscErrorCode      ierr;
1294   Mat_SeqAIJ          *a = (Mat_SeqAIJ*)A->data;
1295   Mat_MatTransMatMult *atb = a->atb;
1296 
1297   PetscFunctionBegin;
1298   ierr = MatDestroy(&atb->At);CHKERRQ(ierr);
1299   ierr = (atb->destroy)(A);CHKERRQ(ierr);
1300   ierr = PetscFree(atb);CHKERRQ(ierr);
1301   PetscFunctionReturn(0);
1302 }
1303 
1304 PetscErrorCode MatTransposeMatMult_SeqAIJ_SeqAIJ(Mat A,Mat B,MatReuse scall,PetscReal fill,Mat *C)
1305 {
1306   PetscErrorCode      ierr;
1307   const char          *algTypes[2] = {"matmatmult","outerproduct"};
1308   PetscInt            alg=0; /* set default algorithm */
1309   Mat                 At;
1310   Mat_MatTransMatMult *atb;
1311   Mat_SeqAIJ          *c;
1312 
1313   PetscFunctionBegin;
1314   if (scall == MAT_INITIAL_MATRIX) {
1315     ierr = PetscObjectOptionsBegin((PetscObject)A);CHKERRQ(ierr);
1316     PetscOptionsObject->alreadyprinted = PETSC_FALSE; /* a hack to ensure the option shows in '-help' */
1317     ierr = PetscOptionsEList("-mattransposematmult_via","Algorithmic approach","MatTransposeMatMult",algTypes,2,algTypes[0],&alg,NULL);CHKERRQ(ierr);
1318     ierr = PetscOptionsEnd();CHKERRQ(ierr);
1319 
1320     switch (alg) {
1321     case 1:
1322       ierr = MatTransposeMatMultSymbolic_SeqAIJ_SeqAIJ(A,B,fill,C);CHKERRQ(ierr);
1323       break;
1324     default:
1325       ierr = PetscNew(&atb);CHKERRQ(ierr);
1326       ierr = MatTranspose_SeqAIJ(A,MAT_INITIAL_MATRIX,&At);CHKERRQ(ierr);
1327       ierr = MatMatMult_SeqAIJ_SeqAIJ(At,B,MAT_INITIAL_MATRIX,fill,C);CHKERRQ(ierr);
1328 
1329       c                  = (Mat_SeqAIJ*)(*C)->data;
1330       c->atb             = atb;
1331       atb->At            = At;
1332       atb->destroy       = (*C)->ops->destroy;
1333       (*C)->ops->destroy = MatDestroy_SeqAIJ_MatTransMatMult;
1334 
1335       break;
1336     }
1337   }
1338   if (alg) {
1339     ierr = (*(*C)->ops->mattransposemultnumeric)(A,B,*C);CHKERRQ(ierr);
1340   } else if (!alg && scall == MAT_REUSE_MATRIX) {
1341     c   = (Mat_SeqAIJ*)(*C)->data;
1342     atb = c->atb;
1343     At  = atb->At;
1344     ierr = MatTranspose_SeqAIJ(A,MAT_REUSE_MATRIX,&At);CHKERRQ(ierr);
1345     ierr = MatMatMult_SeqAIJ_SeqAIJ(At,B,MAT_REUSE_MATRIX,fill,C);CHKERRQ(ierr);
1346   }
1347   PetscFunctionReturn(0);
1348 }
1349 
1350 PetscErrorCode MatTransposeMatMultSymbolic_SeqAIJ_SeqAIJ(Mat A,Mat B,PetscReal fill,Mat *C)
1351 {
1352   PetscErrorCode ierr;
1353   Mat            At;
1354   PetscInt       *ati,*atj;
1355 
1356   PetscFunctionBegin;
1357   /* create symbolic At */
1358   ierr = MatGetSymbolicTranspose_SeqAIJ(A,&ati,&atj);CHKERRQ(ierr);
1359   ierr = MatCreateSeqAIJWithArrays(PETSC_COMM_SELF,A->cmap->n,A->rmap->n,ati,atj,NULL,&At);CHKERRQ(ierr);
1360   ierr = MatSetBlockSizes(At,PetscAbs(A->cmap->bs),PetscAbs(B->cmap->bs));CHKERRQ(ierr);
1361   ierr = MatSetType(At,((PetscObject)A)->type_name);CHKERRQ(ierr);
1362 
1363   /* get symbolic C=At*B */
1364   ierr = MatMatMultSymbolic_SeqAIJ_SeqAIJ(At,B,fill,C);CHKERRQ(ierr);
1365 
1366   /* clean up */
1367   ierr = MatDestroy(&At);CHKERRQ(ierr);
1368   ierr = MatRestoreSymbolicTranspose_SeqAIJ(A,&ati,&atj);CHKERRQ(ierr);
1369 
1370   (*C)->ops->mattransposemultnumeric = MatTransposeMatMultNumeric_SeqAIJ_SeqAIJ;
1371   PetscFunctionReturn(0);
1372 }
1373 
1374 PetscErrorCode MatTransposeMatMultNumeric_SeqAIJ_SeqAIJ(Mat A,Mat B,Mat C)
1375 {
1376   PetscErrorCode ierr;
1377   Mat_SeqAIJ     *a   =(Mat_SeqAIJ*)A->data,*b=(Mat_SeqAIJ*)B->data,*c=(Mat_SeqAIJ*)C->data;
1378   PetscInt       am   =A->rmap->n,anzi,*ai=a->i,*aj=a->j,*bi=b->i,*bj,bnzi,nextb;
1379   PetscInt       cm   =C->rmap->n,*ci=c->i,*cj=c->j,crow,*cjj,i,j,k;
1380   PetscLogDouble flops=0.0;
1381   MatScalar      *aa  =a->a,*ba,*ca,*caj;
1382 
1383   PetscFunctionBegin;
1384   if (!c->a) {
1385     ierr = PetscMalloc1(ci[cm]+1,&ca);CHKERRQ(ierr);
1386 
1387     c->a      = ca;
1388     c->free_a = PETSC_TRUE;
1389   } else {
1390     ca = c->a;
1391   }
1392   /* clear old values in C */
1393   ierr = PetscMemzero(ca,ci[cm]*sizeof(MatScalar));CHKERRQ(ierr);
1394 
1395   /* compute A^T*B using outer product (A^T)[:,i]*B[i,:] */
1396   for (i=0; i<am; i++) {
1397     bj   = b->j + bi[i];
1398     ba   = b->a + bi[i];
1399     bnzi = bi[i+1] - bi[i];
1400     anzi = ai[i+1] - ai[i];
1401     for (j=0; j<anzi; j++) {
1402       nextb = 0;
1403       crow  = *aj++;
1404       cjj   = cj + ci[crow];
1405       caj   = ca + ci[crow];
1406       /* perform sparse axpy operation.  Note cjj includes bj. */
1407       for (k=0; nextb<bnzi; k++) {
1408         if (cjj[k] == *(bj+nextb)) { /* ccol == bcol */
1409           caj[k] += (*aa)*(*(ba+nextb));
1410           nextb++;
1411         }
1412       }
1413       flops += 2*bnzi;
1414       aa++;
1415     }
1416   }
1417 
1418   /* Assemble the final matrix and clean up */
1419   ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1420   ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1421   ierr = PetscLogFlops(flops);CHKERRQ(ierr);
1422   PetscFunctionReturn(0);
1423 }
1424 
1425 PETSC_INTERN PetscErrorCode MatMatMult_SeqAIJ_SeqDense(Mat A,Mat B,MatReuse scall,PetscReal fill,Mat *C)
1426 {
1427   PetscErrorCode ierr;
1428 
1429   PetscFunctionBegin;
1430   if (scall == MAT_INITIAL_MATRIX) {
1431     ierr = PetscLogEventBegin(MAT_MatMultSymbolic,A,B,0,0);CHKERRQ(ierr);
1432     ierr = MatMatMultSymbolic_SeqAIJ_SeqDense(A,B,fill,C);CHKERRQ(ierr);
1433     ierr = PetscLogEventEnd(MAT_MatMultSymbolic,A,B,0,0);CHKERRQ(ierr);
1434   }
1435   ierr = PetscLogEventBegin(MAT_MatMultNumeric,A,B,0,0);CHKERRQ(ierr);
1436   ierr = MatMatMultNumeric_SeqAIJ_SeqDense(A,B,*C);CHKERRQ(ierr);
1437   ierr = PetscLogEventEnd(MAT_MatMultNumeric,A,B,0,0);CHKERRQ(ierr);
1438   PetscFunctionReturn(0);
1439 }
1440 
1441 PetscErrorCode MatMatMultSymbolic_SeqAIJ_SeqDense(Mat A,Mat B,PetscReal fill,Mat *C)
1442 {
1443   PetscErrorCode ierr;
1444 
1445   PetscFunctionBegin;
1446   ierr = MatMatMultSymbolic_SeqDense_SeqDense(A,B,0.0,C);CHKERRQ(ierr);
1447 
1448   (*C)->ops->matmultnumeric = MatMatMultNumeric_SeqAIJ_SeqDense;
1449   PetscFunctionReturn(0);
1450 }
1451 
1452 PetscErrorCode MatMatMultNumeric_SeqAIJ_SeqDense(Mat A,Mat B,Mat C)
1453 {
1454   Mat_SeqAIJ        *a=(Mat_SeqAIJ*)A->data;
1455   Mat_SeqDense      *bd = (Mat_SeqDense*)B->data;
1456   PetscErrorCode    ierr;
1457   PetscScalar       *c,*b,r1,r2,r3,r4,*c1,*c2,*c3,*c4,aatmp;
1458   const PetscScalar *aa,*b1,*b2,*b3,*b4;
1459   const PetscInt    *aj;
1460   PetscInt          cm=C->rmap->n,cn=B->cmap->n,bm=bd->lda,am=A->rmap->n;
1461   PetscInt          am4=4*am,bm4=4*bm,col,i,j,n,ajtmp;
1462 
1463   PetscFunctionBegin;
1464   if (!cm || !cn) PetscFunctionReturn(0);
1465   if (B->rmap->n != A->cmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Number columns in A %D not equal rows in B %D\n",A->cmap->n,B->rmap->n);
1466   if (A->rmap->n != C->rmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Number rows in C %D not equal rows in A %D\n",C->rmap->n,A->rmap->n);
1467   if (B->cmap->n != C->cmap->n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Number columns in B %D not equal columns in C %D\n",B->cmap->n,C->cmap->n);
1468   b = bd->v;
1469   ierr = MatDenseGetArray(C,&c);CHKERRQ(ierr);
1470   b1 = b; b2 = b1 + bm; b3 = b2 + bm; b4 = b3 + bm;
1471   c1 = c; c2 = c1 + am; c3 = c2 + am; c4 = c3 + am;
1472   for (col=0; col<cn-4; col += 4) {  /* over columns of C */
1473     for (i=0; i<am; i++) {        /* over rows of C in those columns */
1474       r1 = r2 = r3 = r4 = 0.0;
1475       n  = a->i[i+1] - a->i[i];
1476       aj = a->j + a->i[i];
1477       aa = a->a + a->i[i];
1478       for (j=0; j<n; j++) {
1479         aatmp = aa[j]; ajtmp = aj[j];
1480         r1 += aatmp*b1[ajtmp];
1481         r2 += aatmp*b2[ajtmp];
1482         r3 += aatmp*b3[ajtmp];
1483         r4 += aatmp*b4[ajtmp];
1484       }
1485       c1[i] = r1;
1486       c2[i] = r2;
1487       c3[i] = r3;
1488       c4[i] = r4;
1489     }
1490     b1 += bm4; b2 += bm4; b3 += bm4; b4 += bm4;
1491     c1 += am4; c2 += am4; c3 += am4; c4 += am4;
1492   }
1493   for (; col<cn; col++) {   /* over extra columns of C */
1494     for (i=0; i<am; i++) {  /* over rows of C in those columns */
1495       r1 = 0.0;
1496       n  = a->i[i+1] - a->i[i];
1497       aj = a->j + a->i[i];
1498       aa = a->a + a->i[i];
1499       for (j=0; j<n; j++) {
1500         r1 += aa[j]*b1[aj[j]];
1501       }
1502       c1[i] = r1;
1503     }
1504     b1 += bm;
1505     c1 += am;
1506   }
1507   ierr = PetscLogFlops(cn*(2.0*a->nz));CHKERRQ(ierr);
1508   ierr = MatDenseRestoreArray(C,&c);CHKERRQ(ierr);
1509   ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1510   ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1511   PetscFunctionReturn(0);
1512 }
1513 
1514 /*
1515    Note very similar to MatMult_SeqAIJ(), should generate both codes from same base
1516 */
1517 PetscErrorCode MatMatMultNumericAdd_SeqAIJ_SeqDense(Mat A,Mat B,Mat C)
1518 {
1519   Mat_SeqAIJ     *a=(Mat_SeqAIJ*)A->data;
1520   Mat_SeqDense   *bd = (Mat_SeqDense*)B->data;
1521   PetscErrorCode ierr;
1522   PetscScalar    *b,*c,r1,r2,r3,r4,*b1,*b2,*b3,*b4;
1523   MatScalar      *aa;
1524   PetscInt       cm  = C->rmap->n, cn=B->cmap->n, bm=bd->lda, col, i,j,n,*aj, am = A->rmap->n,*ii,arm;
1525   PetscInt       am2 = 2*am, am3 = 3*am,  bm4 = 4*bm,colam,*ridx;
1526 
1527   PetscFunctionBegin;
1528   if (!cm || !cn) PetscFunctionReturn(0);
1529   b = bd->v;
1530   ierr = MatDenseGetArray(C,&c);CHKERRQ(ierr);
1531   b1   = b; b2 = b1 + bm; b3 = b2 + bm; b4 = b3 + bm;
1532 
1533   if (a->compressedrow.use) { /* use compressed row format */
1534     for (col=0; col<cn-4; col += 4) {  /* over columns of C */
1535       colam = col*am;
1536       arm   = a->compressedrow.nrows;
1537       ii    = a->compressedrow.i;
1538       ridx  = a->compressedrow.rindex;
1539       for (i=0; i<arm; i++) {        /* over rows of C in those columns */
1540         r1 = r2 = r3 = r4 = 0.0;
1541         n  = ii[i+1] - ii[i];
1542         aj = a->j + ii[i];
1543         aa = a->a + ii[i];
1544         for (j=0; j<n; j++) {
1545           r1 += (*aa)*b1[*aj];
1546           r2 += (*aa)*b2[*aj];
1547           r3 += (*aa)*b3[*aj];
1548           r4 += (*aa++)*b4[*aj++];
1549         }
1550         c[colam       + ridx[i]] += r1;
1551         c[colam + am  + ridx[i]] += r2;
1552         c[colam + am2 + ridx[i]] += r3;
1553         c[colam + am3 + ridx[i]] += r4;
1554       }
1555       b1 += bm4;
1556       b2 += bm4;
1557       b3 += bm4;
1558       b4 += bm4;
1559     }
1560     for (; col<cn; col++) {     /* over extra columns of C */
1561       colam = col*am;
1562       arm   = a->compressedrow.nrows;
1563       ii    = a->compressedrow.i;
1564       ridx  = a->compressedrow.rindex;
1565       for (i=0; i<arm; i++) {  /* over rows of C in those columns */
1566         r1 = 0.0;
1567         n  = ii[i+1] - ii[i];
1568         aj = a->j + ii[i];
1569         aa = a->a + ii[i];
1570 
1571         for (j=0; j<n; j++) {
1572           r1 += (*aa++)*b1[*aj++];
1573         }
1574         c[colam + ridx[i]] += r1;
1575       }
1576       b1 += bm;
1577     }
1578   } else {
1579     for (col=0; col<cn-4; col += 4) {  /* over columns of C */
1580       colam = col*am;
1581       for (i=0; i<am; i++) {        /* over rows of C in those columns */
1582         r1 = r2 = r3 = r4 = 0.0;
1583         n  = a->i[i+1] - a->i[i];
1584         aj = a->j + a->i[i];
1585         aa = a->a + a->i[i];
1586         for (j=0; j<n; j++) {
1587           r1 += (*aa)*b1[*aj];
1588           r2 += (*aa)*b2[*aj];
1589           r3 += (*aa)*b3[*aj];
1590           r4 += (*aa++)*b4[*aj++];
1591         }
1592         c[colam + i]       += r1;
1593         c[colam + am + i]  += r2;
1594         c[colam + am2 + i] += r3;
1595         c[colam + am3 + i] += r4;
1596       }
1597       b1 += bm4;
1598       b2 += bm4;
1599       b3 += bm4;
1600       b4 += bm4;
1601     }
1602     for (; col<cn; col++) {     /* over extra columns of C */
1603       colam = col*am;
1604       for (i=0; i<am; i++) {  /* over rows of C in those columns */
1605         r1 = 0.0;
1606         n  = a->i[i+1] - a->i[i];
1607         aj = a->j + a->i[i];
1608         aa = a->a + a->i[i];
1609 
1610         for (j=0; j<n; j++) {
1611           r1 += (*aa++)*b1[*aj++];
1612         }
1613         c[colam + i] += r1;
1614       }
1615       b1 += bm;
1616     }
1617   }
1618   ierr = PetscLogFlops(cn*2.0*a->nz);CHKERRQ(ierr);
1619   ierr = MatDenseRestoreArray(C,&c);CHKERRQ(ierr);
1620   PetscFunctionReturn(0);
1621 }
1622 
1623 PetscErrorCode  MatTransColoringApplySpToDen_SeqAIJ(MatTransposeColoring coloring,Mat B,Mat Btdense)
1624 {
1625   PetscErrorCode ierr;
1626   Mat_SeqAIJ     *b       = (Mat_SeqAIJ*)B->data;
1627   Mat_SeqDense   *btdense = (Mat_SeqDense*)Btdense->data;
1628   PetscInt       *bi      = b->i,*bj=b->j;
1629   PetscInt       m        = Btdense->rmap->n,n=Btdense->cmap->n,j,k,l,col,anz,*btcol,brow,ncolumns;
1630   MatScalar      *btval,*btval_den,*ba=b->a;
1631   PetscInt       *columns=coloring->columns,*colorforcol=coloring->colorforcol,ncolors=coloring->ncolors;
1632 
1633   PetscFunctionBegin;
1634   btval_den=btdense->v;
1635   ierr     = PetscMemzero(btval_den,(m*n)*sizeof(MatScalar));CHKERRQ(ierr);
1636   for (k=0; k<ncolors; k++) {
1637     ncolumns = coloring->ncolumns[k];
1638     for (l=0; l<ncolumns; l++) { /* insert a row of B to a column of Btdense */
1639       col   = *(columns + colorforcol[k] + l);
1640       btcol = bj + bi[col];
1641       btval = ba + bi[col];
1642       anz   = bi[col+1] - bi[col];
1643       for (j=0; j<anz; j++) {
1644         brow            = btcol[j];
1645         btval_den[brow] = btval[j];
1646       }
1647     }
1648     btval_den += m;
1649   }
1650   PetscFunctionReturn(0);
1651 }
1652 
1653 PetscErrorCode MatTransColoringApplyDenToSp_SeqAIJ(MatTransposeColoring matcoloring,Mat Cden,Mat Csp)
1654 {
1655   PetscErrorCode ierr;
1656   Mat_SeqAIJ     *csp = (Mat_SeqAIJ*)Csp->data;
1657   PetscScalar    *ca_den,*ca_den_ptr,*ca=csp->a;
1658   PetscInt       k,l,m=Cden->rmap->n,ncolors=matcoloring->ncolors;
1659   PetscInt       brows=matcoloring->brows,*den2sp=matcoloring->den2sp;
1660   PetscInt       nrows,*row,*idx;
1661   PetscInt       *rows=matcoloring->rows,*colorforrow=matcoloring->colorforrow;
1662 
1663   PetscFunctionBegin;
1664   ierr   = MatDenseGetArray(Cden,&ca_den);CHKERRQ(ierr);
1665 
1666   if (brows > 0) {
1667     PetscInt *lstart,row_end,row_start;
1668     lstart = matcoloring->lstart;
1669     ierr = PetscMemzero(lstart,ncolors*sizeof(PetscInt));CHKERRQ(ierr);
1670 
1671     row_end = brows;
1672     if (row_end > m) row_end = m;
1673     for (row_start=0; row_start<m; row_start+=brows) { /* loop over row blocks of Csp */
1674       ca_den_ptr = ca_den;
1675       for (k=0; k<ncolors; k++) { /* loop over colors (columns of Cden) */
1676         nrows = matcoloring->nrows[k];
1677         row   = rows  + colorforrow[k];
1678         idx   = den2sp + colorforrow[k];
1679         for (l=lstart[k]; l<nrows; l++) {
1680           if (row[l] >= row_end) {
1681             lstart[k] = l;
1682             break;
1683           } else {
1684             ca[idx[l]] = ca_den_ptr[row[l]];
1685           }
1686         }
1687         ca_den_ptr += m;
1688       }
1689       row_end += brows;
1690       if (row_end > m) row_end = m;
1691     }
1692   } else { /* non-blocked impl: loop over columns of Csp - slow if Csp is large */
1693     ca_den_ptr = ca_den;
1694     for (k=0; k<ncolors; k++) {
1695       nrows = matcoloring->nrows[k];
1696       row   = rows  + colorforrow[k];
1697       idx   = den2sp + colorforrow[k];
1698       for (l=0; l<nrows; l++) {
1699         ca[idx[l]] = ca_den_ptr[row[l]];
1700       }
1701       ca_den_ptr += m;
1702     }
1703   }
1704 
1705   ierr = MatDenseRestoreArray(Cden,&ca_den);CHKERRQ(ierr);
1706 #if defined(PETSC_USE_INFO)
1707   if (matcoloring->brows > 0) {
1708     ierr = PetscInfo1(Csp,"Loop over %D row blocks for den2sp\n",brows);CHKERRQ(ierr);
1709   } else {
1710     ierr = PetscInfo(Csp,"Loop over colors/columns of Cden, inefficient for large sparse matrix product \n");CHKERRQ(ierr);
1711   }
1712 #endif
1713   PetscFunctionReturn(0);
1714 }
1715 
1716 PetscErrorCode MatTransposeColoringCreate_SeqAIJ(Mat mat,ISColoring iscoloring,MatTransposeColoring c)
1717 {
1718   PetscErrorCode ierr;
1719   PetscInt       i,n,nrows,Nbs,j,k,m,ncols,col,cm;
1720   const PetscInt *is,*ci,*cj,*row_idx;
1721   PetscInt       nis = iscoloring->n,*rowhit,bs = 1;
1722   IS             *isa;
1723   Mat_SeqAIJ     *csp = (Mat_SeqAIJ*)mat->data;
1724   PetscInt       *colorforrow,*rows,*rows_i,*idxhit,*spidx,*den2sp,*den2sp_i;
1725   PetscInt       *colorforcol,*columns,*columns_i,brows;
1726   PetscBool      flg;
1727 
1728   PetscFunctionBegin;
1729   ierr = ISColoringGetIS(iscoloring,PETSC_IGNORE,&isa);CHKERRQ(ierr);
1730 
1731   /* bs >1 is not being tested yet! */
1732   Nbs       = mat->cmap->N/bs;
1733   c->M      = mat->rmap->N/bs;  /* set total rows, columns and local rows */
1734   c->N      = Nbs;
1735   c->m      = c->M;
1736   c->rstart = 0;
1737   c->brows  = 100;
1738 
1739   c->ncolors = nis;
1740   ierr = PetscMalloc3(nis,&c->ncolumns,nis,&c->nrows,nis+1,&colorforrow);CHKERRQ(ierr);
1741   ierr = PetscMalloc1(csp->nz+1,&rows);CHKERRQ(ierr);
1742   ierr = PetscMalloc1(csp->nz+1,&den2sp);CHKERRQ(ierr);
1743 
1744   brows = c->brows;
1745   ierr = PetscOptionsGetInt(NULL,NULL,"-matden2sp_brows",&brows,&flg);CHKERRQ(ierr);
1746   if (flg) c->brows = brows;
1747   if (brows > 0) {
1748     ierr = PetscMalloc1(nis+1,&c->lstart);CHKERRQ(ierr);
1749   }
1750 
1751   colorforrow[0] = 0;
1752   rows_i         = rows;
1753   den2sp_i       = den2sp;
1754 
1755   ierr = PetscMalloc1(nis+1,&colorforcol);CHKERRQ(ierr);
1756   ierr = PetscMalloc1(Nbs+1,&columns);CHKERRQ(ierr);
1757 
1758   colorforcol[0] = 0;
1759   columns_i      = columns;
1760 
1761   /* get column-wise storage of mat */
1762   ierr = MatGetColumnIJ_SeqAIJ_Color(mat,0,PETSC_FALSE,PETSC_FALSE,&ncols,&ci,&cj,&spidx,NULL);CHKERRQ(ierr);
1763 
1764   cm   = c->m;
1765   ierr = PetscMalloc1(cm+1,&rowhit);CHKERRQ(ierr);
1766   ierr = PetscMalloc1(cm+1,&idxhit);CHKERRQ(ierr);
1767   for (i=0; i<nis; i++) { /* loop over color */
1768     ierr = ISGetLocalSize(isa[i],&n);CHKERRQ(ierr);
1769     ierr = ISGetIndices(isa[i],&is);CHKERRQ(ierr);
1770 
1771     c->ncolumns[i] = n;
1772     if (n) {
1773       ierr = PetscMemcpy(columns_i,is,n*sizeof(PetscInt));CHKERRQ(ierr);
1774     }
1775     colorforcol[i+1] = colorforcol[i] + n;
1776     columns_i       += n;
1777 
1778     /* fast, crude version requires O(N*N) work */
1779     ierr = PetscMemzero(rowhit,cm*sizeof(PetscInt));CHKERRQ(ierr);
1780 
1781     for (j=0; j<n; j++) { /* loop over columns*/
1782       col     = is[j];
1783       row_idx = cj + ci[col];
1784       m       = ci[col+1] - ci[col];
1785       for (k=0; k<m; k++) { /* loop over columns marking them in rowhit */
1786         idxhit[*row_idx]   = spidx[ci[col] + k];
1787         rowhit[*row_idx++] = col + 1;
1788       }
1789     }
1790     /* count the number of hits */
1791     nrows = 0;
1792     for (j=0; j<cm; j++) {
1793       if (rowhit[j]) nrows++;
1794     }
1795     c->nrows[i]      = nrows;
1796     colorforrow[i+1] = colorforrow[i] + nrows;
1797 
1798     nrows = 0;
1799     for (j=0; j<cm; j++) { /* loop over rows */
1800       if (rowhit[j]) {
1801         rows_i[nrows]   = j;
1802         den2sp_i[nrows] = idxhit[j];
1803         nrows++;
1804       }
1805     }
1806     den2sp_i += nrows;
1807 
1808     ierr    = ISRestoreIndices(isa[i],&is);CHKERRQ(ierr);
1809     rows_i += nrows;
1810   }
1811   ierr = MatRestoreColumnIJ_SeqAIJ_Color(mat,0,PETSC_FALSE,PETSC_FALSE,&ncols,&ci,&cj,&spidx,NULL);CHKERRQ(ierr);
1812   ierr = PetscFree(rowhit);CHKERRQ(ierr);
1813   ierr = ISColoringRestoreIS(iscoloring,&isa);CHKERRQ(ierr);
1814   if (csp->nz != colorforrow[nis]) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"csp->nz %d != colorforrow[nis] %d",csp->nz,colorforrow[nis]);
1815 
1816   c->colorforrow = colorforrow;
1817   c->rows        = rows;
1818   c->den2sp      = den2sp;
1819   c->colorforcol = colorforcol;
1820   c->columns     = columns;
1821 
1822   ierr = PetscFree(idxhit);CHKERRQ(ierr);
1823   PetscFunctionReturn(0);
1824 }
1825 
1826 /* Needed for MatMatMult_SeqAIJ_SeqAIJ_Combined() */
1827 /* Append value to an array if the value is not present yet. A bitarray */
1828 /* was used to determine if there is already an entry at this position. */
1829 void appendToArray(PetscInt val, PetscInt *array, PetscInt *cnzi)
1830 {
1831   array[(*cnzi)++] = val;
1832 }
1833 
1834 /* This algorithm combines the symbolic and numeric phase of matrix-matrix multiplication. */
1835 PetscErrorCode MatMatMult_SeqAIJ_SeqAIJ_Combined(Mat A,Mat B,PetscReal fill,Mat *C)
1836 {
1837   PetscErrorCode     ierr;
1838   PetscLogDouble     flops=0.0;
1839   Mat_SeqAIJ         *a  = (Mat_SeqAIJ*)A->data, *b = (Mat_SeqAIJ*)B->data, *c;
1840   const PetscInt     *ai = a->i,*bi = b->i, *aj = a->j;
1841   PetscInt           *ci,*cj,*cj_i;
1842   PetscScalar        *ca, *ca_i;
1843   PetscInt           c_maxmem = 0, a_maxrownnz = 0, a_rownnz, a_col;
1844   PetscInt           am = A->rmap->N, bn = B->cmap->N, bm = B->rmap->N;
1845   PetscInt           i, k, ndouble = 0;
1846   PetscReal          afill;
1847   PetscScalar        *c_row_val_dense;
1848   PetscBool          *c_row_idx_flags;
1849   PetscInt           *aj_i = a->j;
1850   PetscScalar        *aa_i = a->a;
1851 
1852   PetscFunctionBegin;
1853   /* Step 1: Determine upper bounds on memory for C */
1854   for (i=0; i<am; i++) { /* iterate over all rows of A */
1855     const PetscInt anzi  = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
1856     const PetscInt *acol = aj + ai[i]; /* column indices of nonzero entries in this row */
1857     a_rownnz = 0;
1858     for (k=0;k<anzi;++k) a_rownnz += bi[acol[k]+1] - bi[acol[k]];
1859     a_maxrownnz = PetscMax(a_maxrownnz, a_rownnz);
1860     c_maxmem += a_rownnz;
1861   }
1862   ierr = PetscMalloc1(am+1, &ci);               CHKERRQ(ierr);
1863   ierr = PetscMalloc1(bn, &c_row_val_dense);    CHKERRQ(ierr);
1864   ierr = PetscMalloc1(bn, &c_row_idx_flags);    CHKERRQ(ierr);
1865   ierr = PetscMalloc1(c_maxmem,&cj);            CHKERRQ(ierr);
1866   ierr = PetscMalloc1(c_maxmem,&ca);            CHKERRQ(ierr);
1867   ca_i = ca;
1868   cj_i = cj;
1869   ci[0] = 0;
1870   ierr = PetscMemzero(c_row_val_dense, bn * sizeof(PetscScalar));CHKERRQ(ierr);
1871   ierr = PetscMemzero(c_row_idx_flags, bn * sizeof(PetscBool));CHKERRQ(ierr);
1872   for (i=0; i<am; i++) {
1873     /* Step 2: Initialize the dense row vector for C  */
1874     const PetscInt anzi     = ai[i+1] - ai[i]; /* number of nonzeros in this row of A, this is the number of rows of B that we merge */
1875     PetscInt cnzi           = 0;
1876     PetscInt *bj_i;
1877     PetscScalar *ba_i;
1878 
1879     /* Step 3: Do the numerical calculations */
1880     for (a_col=0; a_col<anzi; a_col++) {          /* iterate over all non zero values in a row of A */
1881       PetscInt a_col_index = aj_i[a_col];
1882       const PetscInt bnzi = bi[a_col_index+1] - bi[a_col_index];
1883       flops += 2*bnzi;
1884       bj_i = b->j + bi[a_col_index];   /* points to the current row in bj */
1885       ba_i = b->a + bi[a_col_index];   /* points to the current row in ba */
1886       for (k=0; k<bnzi; ++k) { /* iterate over all non zeros of this row in B */
1887         if (c_row_idx_flags[ bj_i[k] ] == PETSC_FALSE) {
1888           appendToArray(bj_i[k], cj_i, &cnzi);
1889           c_row_idx_flags[ bj_i[k] ] = PETSC_TRUE;
1890         }
1891         c_row_val_dense[ bj_i[k] ] += aa_i[a_col] * ba_i[k];
1892       }
1893     }
1894 
1895     /* Sort array */
1896     ierr = PetscSortInt(cnzi, cj_i);CHKERRQ(ierr);
1897     /* Step 4 */
1898     for (k=0; k < cnzi; k++) {
1899       ca_i[k] = c_row_val_dense[cj_i[k]];
1900       c_row_val_dense[cj_i[k]] = 0.;
1901       c_row_idx_flags[cj_i[k]] = PETSC_FALSE;
1902     }
1903     /* terminate current row */
1904     aa_i += anzi;
1905     aj_i += anzi;
1906     ca_i += cnzi;
1907     cj_i += cnzi;
1908     ci[i+1] = ci[i] + cnzi;
1909     flops += cnzi;
1910   }
1911 
1912   /* Step 5 */
1913   /* Create the new matrix */
1914   ierr = MatCreateSeqAIJWithArrays(PetscObjectComm((PetscObject)A),am,bn,ci,cj,NULL,C);CHKERRQ(ierr);
1915   ierr = MatSetBlockSizesFromMats(*C,A,B);CHKERRQ(ierr);
1916   ierr = MatSetType(*C,((PetscObject)A)->type_name);CHKERRQ(ierr);
1917 
1918   /* MatCreateSeqAIJWithArrays flags matrix so PETSc doesn't free the user's arrays. */
1919   /* These are PETSc arrays, so change flags so arrays can be deleted by PETSc */
1920   c          = (Mat_SeqAIJ*)((*C)->data);
1921   c->a       = ca;
1922   c->free_a  = PETSC_TRUE;
1923   c->free_ij = PETSC_TRUE;
1924   c->nonew   = 0;
1925 
1926   /* set MatInfo */
1927   afill = (PetscReal)ci[am]/(ai[am]+bi[bm]) + 1.e-5;
1928   if (afill < 1.0) afill = 1.0;
1929   c->maxnz                     = ci[am];
1930   c->nz                        = ci[am];
1931   (*C)->info.mallocs           = ndouble;
1932   (*C)->info.fill_ratio_given  = fill;
1933   (*C)->info.fill_ratio_needed = afill;
1934 
1935   ierr = PetscFree(c_row_val_dense);CHKERRQ(ierr);
1936   ierr = PetscFree(c_row_idx_flags);CHKERRQ(ierr);
1937 
1938   ierr = MatAssemblyBegin(*C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1939   ierr = MatAssemblyEnd(*C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
1940   ierr = PetscLogFlops(flops);CHKERRQ(ierr);
1941   PetscFunctionReturn(0);
1942 }
1943