Actual source code: hem.c

  1: #include <petsc/private/matimpl.h>
  2: #include <../src/mat/impls/aij/seq/aij.h>
  3: #include <../src/mat/impls/aij/mpi/mpiaij.h>
  4: #include <petscdm.h>

  6: /* linked list methods
  7:  *
  8:  *  PetscCDCreate
  9:  */
 10: PetscErrorCode PetscCDCreate(PetscInt a_size, PetscCoarsenData **a_out)
 11: {
 12:   PetscCoarsenData *ail;

 14:   PetscFunctionBegin;
 15:   /* allocate pool, partially */
 16:   PetscCall(PetscNew(&ail));
 17:   *a_out               = ail;
 18:   ail->pool_list.next  = NULL;
 19:   ail->pool_list.array = NULL;
 20:   ail->chk_sz          = 0;
 21:   /* allocate array */
 22:   ail->size = a_size;
 23:   PetscCall(PetscCalloc1(a_size, &ail->array));
 24:   ail->extra_nodes = NULL;
 25:   ail->mat         = NULL;
 26:   PetscFunctionReturn(PETSC_SUCCESS);
 27: }

 29: /* PetscCDDestroy
 30:  */
 31: PetscErrorCode PetscCDDestroy(PetscCoarsenData *ail)
 32: {
 33:   PetscCDArrNd *n = &ail->pool_list;

 35:   PetscFunctionBegin;
 36:   n = n->next;
 37:   while (n) {
 38:     PetscCDArrNd *lstn = n;

 40:     n = n->next;
 41:     PetscCall(PetscFree(lstn));
 42:   }
 43:   if (ail->pool_list.array) PetscCall(PetscFree(ail->pool_list.array));
 44:   PetscCall(PetscFree(ail->array));
 45:   if (ail->mat) PetscCall(MatDestroy(&ail->mat));
 46:   /* delete this (+agg+pool array) */
 47:   PetscCall(PetscFree(ail));
 48:   PetscFunctionReturn(PETSC_SUCCESS);
 49: }

 51: /* PetscCDSetChunkSize
 52:  */
 53: PetscErrorCode PetscCDSetChunkSize(PetscCoarsenData *ail, PetscInt a_sz)
 54: {
 55:   PetscFunctionBegin;
 56:   ail->chk_sz = a_sz;
 57:   PetscFunctionReturn(PETSC_SUCCESS);
 58: }

 60: /*  PetscCDGetNewNode
 61:  */
 62: static PetscErrorCode PetscCDGetNewNode(PetscCoarsenData *ail, PetscCDIntNd **a_out, PetscInt a_id)
 63: {
 64:   PetscFunctionBegin;
 65:   *a_out = NULL; /* squelch -Wmaybe-uninitialized */
 66:   if (ail->extra_nodes) {
 67:     PetscCDIntNd *node = ail->extra_nodes;

 69:     ail->extra_nodes = node->next;
 70:     node->gid        = a_id;
 71:     node->next       = NULL;
 72:     *a_out           = node;
 73:   } else {
 74:     if (!ail->pool_list.array) {
 75:       if (!ail->chk_sz) ail->chk_sz = 10; /* use a chuck size of ail->size? */
 76:       PetscCall(PetscMalloc1(ail->chk_sz, &ail->pool_list.array));
 77:       ail->new_node       = ail->pool_list.array;
 78:       ail->new_left       = ail->chk_sz;
 79:       ail->new_node->next = NULL;
 80:     } else if (!ail->new_left) {
 81:       PetscCDArrNd *node;

 83:       PetscCall(PetscMalloc(ail->chk_sz * sizeof(PetscCDIntNd) + sizeof(PetscCDArrNd), &node));
 84:       node->array         = (PetscCDIntNd *)(node + 1);
 85:       node->next          = ail->pool_list.next;
 86:       ail->pool_list.next = node;
 87:       ail->new_left       = ail->chk_sz;
 88:       ail->new_node       = node->array;
 89:     }
 90:     ail->new_node->gid  = a_id;
 91:     ail->new_node->next = NULL;
 92:     *a_out              = ail->new_node++;
 93:     ail->new_left--;
 94:   }
 95:   PetscFunctionReturn(PETSC_SUCCESS);
 96: }

 98: /* PetscCDIntNdSetID
 99:  */
100: PetscErrorCode PetscCDIntNdSetID(PetscCDIntNd *a_this, PetscInt a_id)
101: {
102:   PetscFunctionBegin;
103:   a_this->gid = a_id;
104:   PetscFunctionReturn(PETSC_SUCCESS);
105: }

107: /* PetscCDIntNdGetID
108:  */
109: PetscErrorCode PetscCDIntNdGetID(const PetscCDIntNd *a_this, PetscInt *a_gid)
110: {
111:   PetscFunctionBegin;
112:   *a_gid = a_this->gid;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /* PetscCDGetHeadPos
117:  */
118: PetscErrorCode PetscCDGetHeadPos(const PetscCoarsenData *ail, PetscInt a_idx, PetscCDIntNd **pos)
119: {
120:   PetscFunctionBegin;
121:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "a_idx >= ail->size: a_idx=%" PetscInt_FMT ".", a_idx);
122:   *pos = ail->array[a_idx];
123:   PetscFunctionReturn(PETSC_SUCCESS);
124: }

126: /* PetscCDGetNextPos
127:  */
128: PetscErrorCode PetscCDGetNextPos(const PetscCoarsenData *ail, PetscInt l_idx, PetscCDIntNd **pos)
129: {
130:   PetscFunctionBegin;
131:   PetscCheck(*pos, PETSC_COMM_SELF, PETSC_ERR_PLIB, "NULL input position.");
132:   *pos = (*pos)->next;
133:   PetscFunctionReturn(PETSC_SUCCESS);
134: }

136: /* PetscCDAppendID
137:  */
138: PetscErrorCode PetscCDAppendID(PetscCoarsenData *ail, PetscInt a_idx, PetscInt a_id)
139: {
140:   PetscCDIntNd *n, *n2;

142:   PetscFunctionBegin;
143:   PetscCall(PetscCDGetNewNode(ail, &n, a_id));
144:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
145:   if (!(n2 = ail->array[a_idx])) ail->array[a_idx] = n;
146:   else {
147:     do {
148:       if (!n2->next) {
149:         n2->next = n;
150:         PetscCheck(!n->next, PETSC_COMM_SELF, PETSC_ERR_PLIB, "n should not have a next");
151:         break;
152:       }
153:       n2 = n2->next;
154:     } while (n2);
155:     PetscCheck(n2, PETSC_COMM_SELF, PETSC_ERR_PLIB, "n2 should be non-null");
156:   }
157:   PetscFunctionReturn(PETSC_SUCCESS);
158: }

160: /* PetscCDAppendNode
161:  */
162: PetscErrorCode PetscCDAppendNode(PetscCoarsenData *ail, PetscInt a_idx, PetscCDIntNd *a_n)
163: {
164:   PetscCDIntNd *n2;

166:   PetscFunctionBegin;
167:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
168:   if (!(n2 = ail->array[a_idx])) ail->array[a_idx] = a_n;
169:   else {
170:     do {
171:       if (!n2->next) {
172:         n2->next  = a_n;
173:         a_n->next = NULL;
174:         break;
175:       }
176:       n2 = n2->next;
177:     } while (n2);
178:     PetscCheck(n2, PETSC_COMM_SELF, PETSC_ERR_PLIB, "n2 should be non-null");
179:   }
180:   PetscFunctionReturn(PETSC_SUCCESS);
181: }

183: /* PetscCDRemoveNextNode: a_last->next, this exposes single linked list structure to API (not used)
184:  */
185: PetscErrorCode PetscCDRemoveNextNode(PetscCoarsenData *ail, PetscInt a_idx, PetscCDIntNd *a_last)
186: {
187:   PetscCDIntNd *del;

189:   PetscFunctionBegin;
190:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
191:   PetscCheck(a_last->next, PETSC_COMM_SELF, PETSC_ERR_PLIB, "a_last should have a next");
192:   del          = a_last->next;
193:   a_last->next = del->next;
194:   /* del->next = NULL; -- this still used in a iterator so keep it intact -- need to fix this with a double linked list */
195:   /* could reuse n2 but PetscCDAppendNode sometimes uses it */
196:   PetscFunctionReturn(PETSC_SUCCESS);
197: }

199: /* PetscCDPrint
200:  */
201: PetscErrorCode PetscCDPrint(const PetscCoarsenData *ail, PetscInt Istart, MPI_Comm comm)
202: {
203:   PetscCDIntNd *n, *n2;
204:   PetscInt      ii;

206:   PetscFunctionBegin;
207:   for (ii = 0; ii < ail->size; ii++) {
208:     n2 = n = ail->array[ii];
209:     if (n) PetscCall(PetscSynchronizedPrintf(comm, "list %" PetscInt_FMT ":", ii + Istart));
210:     while (n) {
211:       PetscCall(PetscSynchronizedPrintf(comm, " %" PetscInt_FMT, n->gid));
212:       n = n->next;
213:     }
214:     if (n2) PetscCall(PetscSynchronizedPrintf(comm, "\n"));
215:   }
216:   PetscCall(PetscSynchronizedFlush(comm, PETSC_STDOUT));
217:   PetscFunctionReturn(PETSC_SUCCESS);
218: }

220: /* PetscCDMoveAppend - take list in a_srcidx and appends to destidx
221:  */
222: PetscErrorCode PetscCDMoveAppend(PetscCoarsenData *ail, PetscInt a_destidx, PetscInt a_srcidx)
223: {
224:   PetscCDIntNd *n;

226:   PetscFunctionBegin;
227:   PetscCheck(a_srcidx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_srcidx);
228:   PetscCheck(a_destidx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_destidx);
229:   PetscCheck(a_destidx != a_srcidx, PETSC_COMM_SELF, PETSC_ERR_PLIB, "a_destidx==a_srcidx %" PetscInt_FMT ".", a_destidx);
230:   n = ail->array[a_destidx];
231:   if (!n) ail->array[a_destidx] = ail->array[a_srcidx];
232:   else {
233:     do {
234:       if (!n->next) {
235:         n->next = ail->array[a_srcidx]; // append
236:         break;
237:       }
238:       n = n->next;
239:     } while (1);
240:   }
241:   ail->array[a_srcidx] = NULL; // empty
242:   PetscFunctionReturn(PETSC_SUCCESS);
243: }

245: /* PetscCDRemoveAllAt - empty one list and move data to cache
246:  */
247: PetscErrorCode PetscCDRemoveAllAt(PetscCoarsenData *ail, PetscInt a_idx)
248: {
249:   PetscCDIntNd *rem, *n1;

251:   PetscFunctionBegin;
252:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
253:   rem               = ail->array[a_idx];
254:   ail->array[a_idx] = NULL;
255:   if (!(n1 = ail->extra_nodes)) ail->extra_nodes = rem;
256:   else {
257:     while (n1->next) n1 = n1->next;
258:     n1->next = rem;
259:   }
260:   PetscFunctionReturn(PETSC_SUCCESS);
261: }

263: /* PetscCDCountAt
264:  */
265: PetscErrorCode PetscCDCountAt(const PetscCoarsenData *ail, PetscInt a_idx, PetscInt *a_sz)
266: {
267:   PetscCDIntNd *n1;
268:   PetscInt      sz = 0;

270:   PetscFunctionBegin;
271:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
272:   n1 = ail->array[a_idx];
273:   while (n1) {
274:     n1 = n1->next;
275:     sz++;
276:   }
277:   *a_sz = sz;
278:   PetscFunctionReturn(PETSC_SUCCESS);
279: }

281: /* PetscCDSize
282:  */
283: PetscErrorCode PetscCDCount(const PetscCoarsenData *ail, PetscInt *a_sz)
284: {
285:   PetscInt sz = 0;

287:   PetscFunctionBegin;
288:   for (PetscInt ii = 0; ii < ail->size; ii++) {
289:     PetscCDIntNd *n1 = ail->array[ii];

291:     while (n1) {
292:       n1 = n1->next;
293:       sz++;
294:     }
295:   }
296:   *a_sz = sz;
297:   PetscFunctionReturn(PETSC_SUCCESS);
298: }

300: /* PetscCDIsEmptyAt - Is the list empty? (not used)
301:  */
302: PetscErrorCode PetscCDIsEmptyAt(const PetscCoarsenData *ail, PetscInt a_idx, PetscBool *a_e)
303: {
304:   PetscFunctionBegin;
305:   PetscCheck(a_idx < ail->size, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index %" PetscInt_FMT " out of range.", a_idx);
306:   *a_e = (PetscBool)(ail->array[a_idx] == NULL);
307:   PetscFunctionReturn(PETSC_SUCCESS);
308: }

310: /* PetscCDGetNonemptyIS - used for C-F methods
311:  */
312: PetscErrorCode PetscCDGetNonemptyIS(PetscCoarsenData *ail, IS *a_mis)
313: {
314:   PetscCDIntNd *n;
315:   PetscInt      ii, kk;
316:   PetscInt     *permute;

318:   PetscFunctionBegin;
319:   for (ii = kk = 0; ii < ail->size; ii++) {
320:     n = ail->array[ii];
321:     if (n) kk++;
322:   }
323:   PetscCall(PetscMalloc1(kk, &permute));
324:   for (ii = kk = 0; ii < ail->size; ii++) {
325:     n = ail->array[ii];
326:     if (n) permute[kk++] = ii;
327:   }
328:   PetscCall(ISCreateGeneral(PETSC_COMM_SELF, kk, permute, PETSC_OWN_POINTER, a_mis));
329:   PetscFunctionReturn(PETSC_SUCCESS);
330: }

332: /* PetscCDGetMat
333:  */
334: PetscErrorCode PetscCDGetMat(PetscCoarsenData *ail, Mat *a_mat)
335: {
336:   PetscFunctionBegin;
337:   *a_mat = ail->mat;
338:   PetscFunctionReturn(PETSC_SUCCESS);
339: }

341: /* PetscCDSetMat
342:  */
343: PetscErrorCode PetscCDSetMat(PetscCoarsenData *ail, Mat a_mat)
344: {
345:   PetscFunctionBegin;
346:   if (ail->mat) {
347:     PetscCall(MatDestroy(&ail->mat)); //should not happen
348:   }
349:   ail->mat = a_mat;
350:   PetscFunctionReturn(PETSC_SUCCESS);
351: }

353: /* PetscCDClearMat
354:  */
355: PetscErrorCode PetscCDClearMat(PetscCoarsenData *ail)
356: {
357:   PetscFunctionBegin;
358:   ail->mat = NULL;
359:   PetscFunctionReturn(PETSC_SUCCESS);
360: }

362: /* PetscCDGetASMBlocks - get IS of aggregates for ASM smoothers
363:  */
364: PetscErrorCode PetscCDGetASMBlocks(const PetscCoarsenData *ail, const PetscInt a_bs, PetscInt *a_sz, IS **a_local_is)
365: {
366:   PetscCDIntNd *n;
367:   PetscInt      lsz, ii, kk, *idxs, jj, gid;
368:   IS           *is_loc = NULL;

370:   PetscFunctionBegin;
371:   for (ii = kk = 0; ii < ail->size; ii++) {
372:     if (ail->array[ii]) kk++;
373:   }
374:   *a_sz = kk;
375:   PetscCall(PetscMalloc1(kk, &is_loc));
376:   for (ii = kk = 0; ii < ail->size; ii++) {
377:     for (lsz = 0, n = ail->array[ii]; n; lsz++, n = n->next) /* void */
378:       ;
379:     if (lsz) {
380:       PetscCall(PetscMalloc1(a_bs * lsz, &idxs));
381:       for (lsz = 0, n = ail->array[ii]; n; n = n->next) {
382:         PetscCall(PetscCDIntNdGetID(n, &gid));
383:         for (jj = 0; jj < a_bs; lsz++, jj++) idxs[lsz] = a_bs * gid + jj;
384:       }
385:       PetscCall(ISCreateGeneral(PETSC_COMM_SELF, lsz, idxs, PETSC_OWN_POINTER, &is_loc[kk++]));
386:     }
387:   }
388:   PetscCheck(*a_sz == kk, PETSC_COMM_SELF, PETSC_ERR_PLIB, "*a_sz %" PetscInt_FMT " != kk %" PetscInt_FMT, *a_sz, kk);
389:   *a_local_is = is_loc; /* out */
390:   PetscFunctionReturn(PETSC_SUCCESS);
391: }

393: /* edge for priority queue */
394: typedef struct edge_tag {
395:   PetscReal weight;
396:   PetscInt  lid0, gid1, ghost1_idx;
397: } Edge;

399: #define MY_MEPS (PETSC_MACHINE_EPSILON * 100)
400: static int gamg_hem_compare(const void *a, const void *b)
401: {
402:   PetscReal va = ((Edge *)a)->weight, vb = ((Edge *)b)->weight;
403:   return (va <= vb - MY_MEPS) ? 1 : (va > vb + MY_MEPS) ? -1 : 0; /* 0 for equal */
404: }

406: /*
407:   MatCoarsenApply_HEM_private - parallel heavy edge matching

409:   Input Parameter:
410:    . a_Gmat - global matrix of the graph
411:    . n_iter - number of matching iterations
412:    . threshold - threshold for filtering graphs

414:   Output Parameter:
415:    . a_locals_llist - array of list of local nodes rooted at local node
416: */
417: static PetscErrorCode MatCoarsenApply_HEM_private(Mat a_Gmat, const PetscInt n_iter, const PetscReal threshold, PetscCoarsenData **a_locals_llist)
418: {
419: #define REQ_BF_SIZE 100
420:   PetscBool         isMPI;
421:   MPI_Comm          comm;
422:   PetscInt          ix, *ii, *aj, Istart, bc_agg = -1, *rbuff = NULL, rbuff_sz = 0;
423:   PetscMPIInt       rank, size, comm_procs[REQ_BF_SIZE], ncomm_procs, *lid_max_pe;
424:   const PetscInt    nloc = a_Gmat->rmap->n, request_size = PetscCeilInt((int)sizeof(MPI_Request), (int)sizeof(PetscInt));
425:   PetscInt         *lid_cprowID;
426:   PetscBool        *lid_matched;
427:   Mat_SeqAIJ       *matA, *matB = NULL;
428:   Mat_MPIAIJ       *mpimat     = NULL;
429:   PetscScalar       one        = 1.;
430:   PetscCoarsenData *agg_llists = NULL, *ghost_deleted_list = NULL, *bc_list = NULL;
431:   Mat               cMat, tMat, P;
432:   MatScalar        *ap;
433:   IS                info_is;

435:   PetscFunctionBegin;
436:   PetscCall(PetscObjectGetComm((PetscObject)a_Gmat, &comm));
437:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
438:   PetscCallMPI(MPI_Comm_size(comm, &size));
439:   PetscCall(MatGetOwnershipRange(a_Gmat, &Istart, NULL));
440:   PetscCall(ISCreate(comm, &info_is));
441:   PetscCall(PetscInfo(info_is, "Start %" PetscInt_FMT " iterations of HEM.\n", n_iter));

443:   PetscCall(PetscMalloc3(nloc, &lid_matched, nloc, &lid_cprowID, nloc, &lid_max_pe));
444:   PetscCall(PetscCDCreate(nloc, &agg_llists));
445:   PetscCall(PetscCDSetChunkSize(agg_llists, nloc + 1));
446:   *a_locals_llist = agg_llists;
447:   /* add self to all lists */
448:   for (PetscInt kk = 0; kk < nloc; kk++) PetscCall(PetscCDAppendID(agg_llists, kk, Istart + kk));
449:   /* make a copy of the graph, this gets destroyed in iterates */
450:   PetscCall(MatDuplicate(a_Gmat, MAT_COPY_VALUES, &cMat));
451:   PetscCall(MatConvert(cMat, MATAIJ, MAT_INPLACE_MATRIX, &cMat));
452:   isMPI = (PetscBool)(size > 1);
453:   if (isMPI) {
454:     /* list of deleted ghosts, should compress this */
455:     PetscCall(PetscCDCreate(size, &ghost_deleted_list));
456:     PetscCall(PetscCDSetChunkSize(ghost_deleted_list, 100));
457:   }
458:   for (PetscInt iter = 0; iter < n_iter; iter++) {
459:     const PetscScalar *lghost_max_ew, *lid_max_ew;
460:     PetscBool         *lghost_matched;
461:     PetscMPIInt       *lghost_pe, *lghost_max_pe;
462:     Vec                locMaxEdge, ghostMaxEdge, ghostMaxPE, locMaxPE;
463:     PetscInt          *lghost_gid, nEdges, nEdges0, num_ghosts = 0;
464:     Edge              *Edges;
465:     const PetscInt     n_sub_its = 1000; // in case of a bug, stop at some point

467:     /* get submatrices of cMat */
468:     for (PetscInt kk = 0; kk < nloc; kk++) lid_cprowID[kk] = -1;
469:     if (isMPI) {
470:       mpimat = (Mat_MPIAIJ *)cMat->data;
471:       matA   = (Mat_SeqAIJ *)mpimat->A->data;
472:       matB   = (Mat_SeqAIJ *)mpimat->B->data;
473:       if (!matB->compressedrow.use) {
474:         /* force construction of compressed row data structure since code below requires it */
475:         PetscCall(MatCheckCompressedRow(mpimat->B, matB->nonzerorowcnt, &matB->compressedrow, matB->i, mpimat->B->rmap->n, -1.0));
476:       }
477:       /* set index into compressed row 'lid_cprowID' */
478:       for (ix = 0; ix < matB->compressedrow.nrows; ix++) {
479:         PetscInt *ridx = matB->compressedrow.rindex, lid = ridx[ix];
480:         if (ridx[ix] >= 0) lid_cprowID[lid] = ix;
481:       }
482:     } else {
483:       matA = (Mat_SeqAIJ *)cMat->data;
484:     }
485:     /* set matched flags: true for empty list */
486:     for (PetscInt kk = 0; kk < nloc; kk++) {
487:       PetscCall(PetscCDCountAt(agg_llists, kk, &ix));
488:       if (ix > 0) lid_matched[kk] = PETSC_FALSE;
489:       else lid_matched[kk] = PETSC_TRUE; // call deleted gids as matched
490:     }
491:     /* max edge and pe vecs */
492:     PetscCall(MatCreateVecs(cMat, &locMaxEdge, NULL));
493:     PetscCall(MatCreateVecs(cMat, &locMaxPE, NULL));
494:     /* get 'lghost_pe' & 'lghost_gid' & init. 'lghost_matched' using 'mpimat->lvec' */
495:     if (isMPI) {
496:       Vec                vec;
497:       PetscScalar        vval;
498:       const PetscScalar *buf;

500:       PetscCall(MatCreateVecs(cMat, &vec, NULL));
501:       PetscCall(VecGetLocalSize(mpimat->lvec, &num_ghosts));
502:       /* lghost_matched */
503:       for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) {
504:         PetscScalar vval = lid_matched[kk] ? 1.0 : 0.0;

506:         PetscCall(VecSetValues(vec, 1, &gid, &vval, INSERT_VALUES));
507:       }
508:       PetscCall(VecAssemblyBegin(vec));
509:       PetscCall(VecAssemblyEnd(vec));
510:       PetscCall(VecScatterBegin(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
511:       PetscCall(VecScatterEnd(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
512:       PetscCall(VecGetArrayRead(mpimat->lvec, &buf)); /* get proc ID in 'buf' */
513:       PetscCall(PetscMalloc4(num_ghosts, &lghost_matched, num_ghosts, &lghost_pe, num_ghosts, &lghost_gid, num_ghosts, &lghost_max_pe));

515:       for (PetscInt kk = 0; kk < num_ghosts; kk++) {
516:         lghost_matched[kk] = (PetscBool)(PetscRealPart(buf[kk]) != 0); // the proc of the ghost for now
517:       }
518:       PetscCall(VecRestoreArrayRead(mpimat->lvec, &buf));
519:       /* lghost_pe */
520:       vval = (PetscScalar)rank;
521:       for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) PetscCall(VecSetValues(vec, 1, &gid, &vval, INSERT_VALUES)); /* set with GID */
522:       PetscCall(VecAssemblyBegin(vec));
523:       PetscCall(VecAssemblyEnd(vec));
524:       PetscCall(VecScatterBegin(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
525:       PetscCall(VecScatterEnd(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
526:       PetscCall(VecGetArrayRead(mpimat->lvec, &buf));                                                   /* get proc ID in 'buf' */
527:       for (PetscInt kk = 0; kk < num_ghosts; kk++) lghost_pe[kk] = (PetscMPIInt)PetscRealPart(buf[kk]); // the proc of the ghost for now
528:       PetscCall(VecRestoreArrayRead(mpimat->lvec, &buf));
529:       /* lghost_gid */
530:       for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) {
531:         vval = (PetscScalar)gid;

533:         PetscCall(VecSetValues(vec, 1, &gid, &vval, INSERT_VALUES)); /* set with GID */
534:       }
535:       PetscCall(VecAssemblyBegin(vec));
536:       PetscCall(VecAssemblyEnd(vec));
537:       PetscCall(VecScatterBegin(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
538:       PetscCall(VecScatterEnd(mpimat->Mvctx, vec, mpimat->lvec, INSERT_VALUES, SCATTER_FORWARD));
539:       PetscCall(VecDestroy(&vec));
540:       PetscCall(VecGetArrayRead(mpimat->lvec, &buf)); /* get proc ID in 'lghost_gid' */
541:       for (PetscInt kk = 0; kk < num_ghosts; kk++) lghost_gid[kk] = (PetscInt)PetscRealPart(buf[kk]);
542:       PetscCall(VecRestoreArrayRead(mpimat->lvec, &buf));
543:     }
544:     // get 'comm_procs' (could hoist)
545:     for (PetscInt kk = 0; kk < REQ_BF_SIZE; kk++) comm_procs[kk] = -1;
546:     for (ix = 0, ncomm_procs = 0; ix < num_ghosts; ix++) {
547:       PetscMPIInt proc = lghost_pe[ix], idx = -1;

549:       for (PetscMPIInt k = 0; k < ncomm_procs && idx == -1; k++)
550:         if (comm_procs[k] == proc) idx = k;
551:       if (idx == -1) comm_procs[ncomm_procs++] = proc;
552:       PetscCheck(ncomm_procs != REQ_BF_SIZE, PETSC_COMM_SELF, PETSC_ERR_SUP, "Receive request array too small: %d", ncomm_procs);
553:     }
554:     /* count edges, compute initial 'locMaxEdge', 'locMaxPE' */
555:     nEdges0 = 0;
556:     for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) {
557:       PetscReal   max_e = 0., tt;
558:       PetscScalar vval;
559:       PetscInt    lid = kk, max_pe = rank, pe, n;

561:       ii = matA->i;
562:       n  = ii[lid + 1] - ii[lid];
563:       aj = PetscSafePointerPlusOffset(matA->j, ii[lid]);
564:       ap = PetscSafePointerPlusOffset(matA->a, ii[lid]);
565:       for (PetscInt jj = 0; jj < n; jj++) {
566:         PetscInt lidj = aj[jj];

568:         if ((tt = PetscRealPart(ap[jj])) > threshold && lidj != lid) {
569:           if (tt > max_e) max_e = tt;
570:           if (lidj > lid) nEdges0++;
571:         }
572:       }
573:       if ((ix = lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
574:         ii = matB->compressedrow.i;
575:         n  = ii[ix + 1] - ii[ix];
576:         ap = matB->a + ii[ix];
577:         aj = matB->j + ii[ix];
578:         for (PetscInt jj = 0; jj < n; jj++) {
579:           if ((tt = PetscRealPart(ap[jj])) > threshold) {
580:             if (tt > max_e) max_e = tt;
581:             nEdges0++;
582:             if ((pe = lghost_pe[aj[jj]]) > max_pe) max_pe = pe;
583:           }
584:         }
585:       }
586:       vval = max_e;
587:       PetscCall(VecSetValues(locMaxEdge, 1, &gid, &vval, INSERT_VALUES));
588:       vval = (PetscScalar)max_pe;
589:       PetscCall(VecSetValues(locMaxPE, 1, &gid, &vval, INSERT_VALUES));
590:       if (iter == 0 && max_e <= MY_MEPS) { // add BCs to fake aggregate
591:         lid_matched[lid] = PETSC_TRUE;
592:         if (bc_agg == -1) {
593:           bc_agg = lid;
594:           PetscCall(PetscCDCreate(1, &bc_list));
595:         }
596:         PetscCall(PetscCDRemoveAllAt(agg_llists, lid));
597:         PetscCall(PetscCDAppendID(bc_list, 0, Istart + lid));
598:       }
599:     }
600:     PetscCall(VecAssemblyBegin(locMaxEdge));
601:     PetscCall(VecAssemblyEnd(locMaxEdge));
602:     PetscCall(VecAssemblyBegin(locMaxPE));
603:     PetscCall(VecAssemblyEnd(locMaxPE));
604:     /* make 'ghostMaxEdge_max_ew', 'lghost_max_pe' */
605:     if (isMPI) {
606:       const PetscScalar *buf;

608:       PetscCall(VecDuplicate(mpimat->lvec, &ghostMaxEdge));
609:       PetscCall(VecScatterBegin(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));
610:       PetscCall(VecScatterEnd(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));

612:       PetscCall(VecDuplicate(mpimat->lvec, &ghostMaxPE));
613:       PetscCall(VecScatterBegin(mpimat->Mvctx, locMaxPE, ghostMaxPE, INSERT_VALUES, SCATTER_FORWARD));
614:       PetscCall(VecScatterEnd(mpimat->Mvctx, locMaxPE, ghostMaxPE, INSERT_VALUES, SCATTER_FORWARD));
615:       PetscCall(VecGetArrayRead(ghostMaxPE, &buf));
616:       for (PetscInt kk = 0; kk < num_ghosts; kk++) lghost_max_pe[kk] = (PetscMPIInt)PetscRealPart(buf[kk]); // the MAX proc of the ghost now
617:       PetscCall(VecRestoreArrayRead(ghostMaxPE, &buf));
618:     }
619:     { // make lid_max_pe
620:       const PetscScalar *buf;

622:       PetscCall(VecGetArrayRead(locMaxPE, &buf));
623:       for (PetscInt kk = 0; kk < nloc; kk++) lid_max_pe[kk] = (PetscMPIInt)PetscRealPart(buf[kk]); // the MAX proc of the ghost now
624:       PetscCall(VecRestoreArrayRead(locMaxPE, &buf));
625:     }
626:     /* setup sorted list of edges, and make 'Edges' */
627:     PetscCall(PetscMalloc1(nEdges0, &Edges));
628:     nEdges = 0;
629:     for (PetscInt kk = 0, n; kk < nloc; kk++) {
630:       const PetscInt lid = kk;
631:       PetscReal      tt;

633:       ii = matA->i;
634:       n  = ii[lid + 1] - ii[lid];
635:       aj = PetscSafePointerPlusOffset(matA->j, ii[lid]);
636:       ap = PetscSafePointerPlusOffset(matA->a, ii[lid]);
637:       for (PetscInt jj = 0; jj < n; jj++) {
638:         PetscInt lidj = aj[jj];

640:         if ((tt = PetscRealPart(ap[jj])) > threshold && lidj != lid) {
641:           if (lidj > lid) {
642:             Edges[nEdges].lid0       = lid;
643:             Edges[nEdges].gid1       = lidj + Istart;
644:             Edges[nEdges].ghost1_idx = -1;
645:             Edges[nEdges].weight     = tt;
646:             nEdges++;
647:           }
648:         }
649:       }
650:       if ((ix = lid_cprowID[lid]) != -1) { /* if I have any ghost neighbor */
651:         ii = matB->compressedrow.i;
652:         n  = ii[ix + 1] - ii[ix];
653:         ap = matB->a + ii[ix];
654:         aj = matB->j + ii[ix];
655:         for (PetscInt jj = 0; jj < n; jj++) {
656:           if ((tt = PetscRealPart(ap[jj])) > threshold) {
657:             Edges[nEdges].lid0       = lid;
658:             Edges[nEdges].gid1       = lghost_gid[aj[jj]];
659:             Edges[nEdges].ghost1_idx = aj[jj];
660:             Edges[nEdges].weight     = tt;
661:             nEdges++;
662:           }
663:         }
664:       }
665:     }
666:     PetscCheck(nEdges == nEdges0, PETSC_COMM_SELF, PETSC_ERR_SUP, "nEdges != nEdges0: %" PetscInt_FMT " %" PetscInt_FMT, nEdges0, nEdges);
667:     if (Edges) qsort(Edges, nEdges, sizeof(Edge), gamg_hem_compare);

669:     PetscCall(PetscInfo(info_is, "[%d] HEM iteration %" PetscInt_FMT " with %" PetscInt_FMT " edges\n", rank, iter, nEdges));

671:     /* projection matrix */
672:     PetscCall(MatCreate(comm, &P));
673:     PetscCall(MatSetType(P, MATAIJ));
674:     PetscCall(MatSetSizes(P, nloc, nloc, PETSC_DETERMINE, PETSC_DETERMINE));
675:     PetscCall(MatMPIAIJSetPreallocation(P, 1, NULL, 1, NULL));
676:     PetscCall(MatSeqAIJSetPreallocation(P, 1, NULL));
677:     PetscCall(MatSetUp(P));
678:     /* process - communicate - process */
679:     for (PetscInt sub_it = 0, old_num_edge = 0; /* sub_it < n_sub_its */; /* sub_it++ */) {
680:       PetscInt    nactive_edges = 0, n_act_n[3], gn_act_n[3];
681:       PetscMPIInt tag1, tag2;

683:       PetscCall(VecGetArrayRead(locMaxEdge, &lid_max_ew));
684:       if (isMPI) {
685:         PetscCall(VecGetArrayRead(ghostMaxEdge, &lghost_max_ew));
686:         PetscCall(PetscCommGetNewTag(comm, &tag1));
687:         PetscCall(PetscCommGetNewTag(comm, &tag2));
688:       }
689:       for (PetscInt kk = 0; kk < nEdges; kk++) {
690:         const Edge    *e    = &Edges[kk];
691:         const PetscInt lid0 = e->lid0, gid1 = e->gid1, ghost1_idx = e->ghost1_idx, gid0 = lid0 + Istart, lid1 = gid1 - Istart;
692:         PetscBool      isOK = PETSC_TRUE, print = PETSC_FALSE;

694:         if (print)
695:           PetscCall(PetscSynchronizedPrintf(comm, "\t[%d] edge (%" PetscInt_FMT " %" PetscInt_FMT "), %s %s %s\n", rank, gid0, gid1, lid_matched[lid0] ? "true" : "false", (ghost1_idx != -1 && lghost_matched[ghost1_idx]) ? "true" : "false", (ghost1_idx == -1 && lid_matched[lid1]) ? "true" : "false"));
696:         /* skip if either vertex is matched already */
697:         if (lid_matched[lid0] || (ghost1_idx != -1 && lghost_matched[ghost1_idx]) || (ghost1_idx == -1 && lid_matched[lid1])) continue;

699:         nactive_edges++;
700:         PetscCheck(PetscRealPart(lid_max_ew[lid0]) >= e->weight - MY_MEPS, PETSC_COMM_SELF, PETSC_ERR_SUP, "edge weight %e > max %e", (double)e->weight, (double)PetscRealPart(lid_max_ew[lid0]));
701:         if (print) PetscCall(PetscSynchronizedPrintf(comm, "\t[%d] active edge (%" PetscInt_FMT " %" PetscInt_FMT "), diff0 = %10.4e\n", rank, gid0, gid1, (double)(PetscRealPart(lid_max_ew[lid0]) - e->weight)));
702:         // smaller edge, lid_max_ew get updated - e0
703:         if (PetscRealPart(lid_max_ew[lid0]) > e->weight + MY_MEPS) {
704:           if (print)
705:             PetscCall(PetscSynchronizedPrintf(comm, "\t\t[%d] 1) e0 SKIPPING small edge %20.14e edge (%" PetscInt_FMT " %" PetscInt_FMT "), diff = %10.4e to proc %d. max = %20.14e, w = %20.14e\n", rank, (double)e->weight, gid0, gid1, (double)(PetscRealPart(lid_max_ew[lid0]) - e->weight), ghost1_idx != -1 ? lghost_pe[ghost1_idx] : rank, (double)PetscRealPart(lid_max_ew[lid0]),
706:                                               (double)e->weight));
707:           continue; // we are basically filter edges here
708:         }
709:         // e1 - local
710:         if (ghost1_idx == -1) {
711:           if (PetscRealPart(lid_max_ew[lid1]) > e->weight + MY_MEPS) {
712:             if (print)
713:               PetscCall(PetscSynchronizedPrintf(comm, "\t\t%c[%d] 2) e1 SKIPPING small local edge %20.14e edge (%" PetscInt_FMT " %" PetscInt_FMT "), diff = %10.4e\n", ghost1_idx != -1 ? '\t' : ' ', rank, (double)e->weight, gid0, gid1, (double)(PetscRealPart(lid_max_ew[lid1]) - e->weight)));
714:             continue; // we are basically filter edges here
715:           }
716:         } else { // e1 - ghost
717:           /* see if edge might get matched on other proc */
718:           PetscReal g_max_e1 = PetscRealPart(lghost_max_ew[ghost1_idx]);

720:           if (print)
721:             PetscCall(PetscSynchronizedPrintf(comm, "\t\t\t[%d] CHECK GHOST e1, edge (%" PetscInt_FMT " %" PetscInt_FMT "), E0 MAX EDGE WEIGHT = %10.4e, EDGE WEIGHT = %10.4e, diff1 = %10.4e, ghost proc %d with max pe %d on e0 and %d on e1\n", rank, gid0, gid1, (double)PetscRealPart(lid_max_ew[lid0]),
722:                                               (double)e->weight, (double)(PetscRealPart(lghost_max_ew[ghost1_idx]) - e->weight), lghost_pe[ghost1_idx], lid_max_pe[lid0], lghost_max_pe[ghost1_idx]));
723:           if (g_max_e1 > e->weight + MY_MEPS) {
724:             /* PetscCall(PetscSynchronizedPrintf(comm,"\t\t\t\t[%d] 3) ghost e1 SKIPPING small edge (%d %d), diff = %10.4e from proc %d with max pe %d. max = %20.14e, w = %20.14e\n", rank, gid0, gid1, g_max_e1 - e->weight, lghost_pe[ghost1_idx], lghost_max_pe[ghost1_idx], g_max_e1, e->weight )); */
725:             continue;
726:           } else if (g_max_e1 >= e->weight - MY_MEPS && lghost_pe[ghost1_idx] > rank) { // is 'lghost_max_pe[ghost1_idx] > rank' needed?
727:             /* check for max_ea == to this edge and larger processor that will deal with this */
728:             if (print)
729:               PetscCall(PetscSynchronizedPrintf(comm, "\t\t\t[%d] ghost e1 SKIPPING EQUAL (%" PetscInt_FMT " %" PetscInt_FMT "), diff = %10.4e from larger proc %d with max pe %d. max = %20.14e, w = %20.14e\n", rank, gid0, gid1, (double)(PetscRealPart(lid_max_ew[lid0]) - e->weight), lghost_pe[ghost1_idx], lghost_max_pe[ghost1_idx], (double)g_max_e1,
730:                                                 (double)e->weight));
731:             continue;
732:           } else {
733:             /* PetscCall(PetscSynchronizedPrintf(comm,"\t[%d] Edge (%d %d) passes gid0 tests, diff = %10.4e from proc %d with max pe %d. max = %20.14e, w = %20.14e\n", rank, gid0, gid1, g_max_e1 - e->weight, lghost_pe[ghost1_idx], lghost_max_pe[ghost1_idx], g_max_e1, e->weight )); */
734:           }
735:         }
736:         /* check ghost for v0 */
737:         if (isOK) {
738:           PetscReal max_e, ew;

740:           if ((ix = lid_cprowID[lid0]) != -1) { /* if I have any ghost neighbors */
741:             PetscInt n;

743:             ii = matB->compressedrow.i;
744:             n  = ii[ix + 1] - ii[ix];
745:             ap = matB->a + ii[ix];
746:             aj = matB->j + ii[ix];
747:             for (PetscInt jj = 0; jj < n && isOK; jj++) {
748:               PetscInt lidj = aj[jj];

750:               if (lghost_matched[lidj]) continue;
751:               ew = PetscRealPart(ap[jj]);
752:               if (ew <= threshold) continue;
753:               max_e = PetscRealPart(lghost_max_ew[lidj]);

755:               /* check for max_e == to this edge and larger processor that will deal with this */
756:               if (ew >= PetscRealPart(lid_max_ew[lid0]) - MY_MEPS && lghost_max_pe[lidj] > rank) isOK = PETSC_FALSE;
757:               PetscCheck(ew <= max_e + MY_MEPS, PETSC_COMM_SELF, PETSC_ERR_SUP, "edge weight %e > max %e. ncols = %" PetscInt_FMT ", gid0 = %" PetscInt_FMT ", gid1 = %" PetscInt_FMT, (double)PetscRealPart(ew), (double)PetscRealPart(max_e), n, lid0 + Istart, lghost_gid[lidj]);
758:               if (print)
759:                 PetscCall(PetscSynchronizedPrintf(comm, "\t\t\t\t[%d] e0: looked at ghost adj (%" PetscInt_FMT " %" PetscInt_FMT "), diff = %10.4e, ghost on proc %d (max %d). isOK = %d, %d %d %d; ew = %e, lid0 max ew = %e, diff = %e, eps = %e\n", rank, gid0, lghost_gid[lidj], (double)(max_e - ew), lghost_pe[lidj], lghost_max_pe[lidj], isOK, (double)ew >= (double)(max_e - MY_MEPS), ew >= PetscRealPart(lid_max_ew[lid0]) - MY_MEPS, lghost_pe[lidj] > rank, (double)ew, (double)PetscRealPart(lid_max_ew[lid0]), (double)(ew - PetscRealPart(lid_max_ew[lid0])), (double)MY_MEPS));
760:             }
761:             if (!isOK && print) PetscCall(PetscSynchronizedPrintf(comm, "\t\t[%d] skip edge (%" PetscInt_FMT " %" PetscInt_FMT ") from ghost inspection\n", rank, gid0, gid1));
762:           }
763:           /* check local v1 */
764:           if (ghost1_idx == -1) {
765:             if ((ix = lid_cprowID[lid1]) != -1) { /* if I have any ghost neighbors */
766:               PetscInt n;

768:               ii = matB->compressedrow.i;
769:               n  = ii[ix + 1] - ii[ix];
770:               ap = matB->a + ii[ix];
771:               aj = matB->j + ii[ix];
772:               for (PetscInt jj = 0; jj < n && isOK; jj++) {
773:                 PetscInt lidj = aj[jj];

775:                 if (lghost_matched[lidj]) continue;
776:                 ew = PetscRealPart(ap[jj]);
777:                 if (ew <= threshold) continue;
778:                 max_e = PetscRealPart(lghost_max_ew[lidj]);
779:                 /* check for max_e == to this edge and larger processor that will deal with this */
780:                 if (ew >= PetscRealPart(lid_max_ew[lid1]) - MY_MEPS && lghost_max_pe[lidj] > rank) isOK = PETSC_FALSE;
781:                 PetscCheck(ew <= max_e + MY_MEPS, PETSC_COMM_SELF, PETSC_ERR_SUP, "edge weight %e > max %e", (double)PetscRealPart(ew), (double)PetscRealPart(max_e));
782:                 if (print)
783:                   PetscCall(PetscSynchronizedPrintf(comm, "\t\t\t\t\t[%d] e1: looked at ghost adj (%" PetscInt_FMT " %" PetscInt_FMT "), diff = %10.4e, ghost on proc %d (max %d)\n", rank, gid0, lghost_gid[lidj], (double)(max_e - ew), lghost_pe[lidj], lghost_max_pe[lidj]));
784:               }
785:             }
786:             if (!isOK && print) PetscCall(PetscSynchronizedPrintf(comm, "\t\t[%d] skip edge (%" PetscInt_FMT " %" PetscInt_FMT ") from ghost inspection\n", rank, gid0, gid1));
787:           }
788:         }
789:         PetscReal e1_max_w = (ghost1_idx == -1 ? PetscRealPart(lid_max_ew[lid0]) : PetscRealPart(lghost_max_ew[ghost1_idx]));
790:         if (print)
791:           PetscCall(PetscSynchronizedPrintf(comm, "\t[%d] MATCHING (%" PetscInt_FMT " %" PetscInt_FMT ") e1 max weight = %e, e1 weight diff %e, %s. isOK = %d\n", rank, gid0, gid1, (double)e1_max_w, (double)(e1_max_w - e->weight), ghost1_idx == -1 ? "local" : "ghost", isOK));
792:         /* do it */
793:         if (isOK) {
794:           if (ghost1_idx == -1) {
795:             PetscCheck(!lid_matched[lid1], PETSC_COMM_SELF, PETSC_ERR_SUP, "local %" PetscInt_FMT " is matched", gid1);
796:             lid_matched[lid1] = PETSC_TRUE;                       /* keep track of what we've done this round */
797:             PetscCall(PetscCDMoveAppend(agg_llists, lid0, lid1)); // takes lid1's list and appends to lid0's
798:           } else {
799:             /* add gid1 to list of ghost deleted by me -- I need their children */
800:             PetscMPIInt proc = lghost_pe[ghost1_idx];
801:             PetscCheck(!lghost_matched[ghost1_idx], PETSC_COMM_SELF, PETSC_ERR_SUP, "ghost %" PetscInt_FMT " is matched", lghost_gid[ghost1_idx]);
802:             lghost_matched[ghost1_idx] = PETSC_TRUE;
803:             PetscCall(PetscCDAppendID(ghost_deleted_list, proc, ghost1_idx)); /* cache to send messages */
804:             PetscCall(PetscCDAppendID(ghost_deleted_list, proc, lid0));
805:           }
806:           lid_matched[lid0] = PETSC_TRUE; /* keep track of what we've done this round */
807:           /* set projection */
808:           PetscCall(MatSetValues(P, 1, &gid0, 1, &gid0, &one, INSERT_VALUES));
809:           PetscCall(MatSetValues(P, 1, &gid1, 1, &gid0, &one, INSERT_VALUES));
810:           //PetscCall(PetscPrintf(comm,"\t %" PetscInt_FMT ".%" PetscInt_FMT ") match active EDGE %" PetscInt_FMT " : (%" PetscInt_FMT " %" PetscInt_FMT ")\n",iter,sub_it, nactive_edges, gid0, gid1));
811:         } /* matched */
812:       } /* edge loop */
813:       PetscCall(PetscSynchronizedFlush(comm, PETSC_STDOUT));
814:       if (isMPI) PetscCall(VecRestoreArrayRead(ghostMaxEdge, &lghost_max_ew));
815:       PetscCall(VecRestoreArrayRead(locMaxEdge, &lid_max_ew));
816:       // count active for test, latter, update deleted ghosts
817:       n_act_n[0] = nactive_edges;
818:       if (ghost_deleted_list) PetscCall(PetscCDCount(ghost_deleted_list, &n_act_n[2]));
819:       else n_act_n[2] = 0;
820:       PetscCall(PetscCDCount(agg_llists, &n_act_n[1]));
821:       PetscCallMPI(MPIU_Allreduce(n_act_n, gn_act_n, 3, MPIU_INT, MPI_SUM, comm));
822:       PetscCall(PetscInfo(info_is, "[%d] %" PetscInt_FMT ".%" PetscInt_FMT ") nactive edges=%" PetscInt_FMT ", ncomm_procs=%d, nEdges=%" PetscInt_FMT ", %" PetscInt_FMT " deleted ghosts, N=%" PetscInt_FMT "\n", rank, iter, sub_it, gn_act_n[0], ncomm_procs, nEdges, gn_act_n[2], gn_act_n[1]));
823:       /* deal with deleted ghost */
824:       if (isMPI) {
825:         PetscCDIntNd *pos;
826:         PetscInt     *sbuffs1[REQ_BF_SIZE], ndel;
827:         PetscInt     *sbuffs2[REQ_BF_SIZE];
828:         MPI_Status    status;

830:         /* send deleted ghosts */
831:         for (PetscInt proc_idx = 0; proc_idx < ncomm_procs; proc_idx++) {
832:           const PetscMPIInt proc = comm_procs[proc_idx];
833:           PetscInt         *sbuff, *pt, scount;
834:           MPI_Request      *request;

836:           /* count ghosts */
837:           PetscCall(PetscCDCountAt(ghost_deleted_list, proc, &ndel));
838:           ndel /= 2; // two entries for each proc
839:           scount = 2 + 2 * ndel;
840:           PetscCall(PetscMalloc1(scount + request_size, &sbuff));
841:           /* save requests */
842:           sbuffs1[proc_idx] = sbuff;
843:           request           = (MPI_Request *)sbuff;
844:           sbuff = pt = sbuff + request_size;
845:           /* write [ndel, proc, n*[gid1,gid0] */
846:           *pt++ = ndel; // number of deleted to send
847:           *pt++ = rank; // proc (not used)
848:           PetscCall(PetscCDGetHeadPos(ghost_deleted_list, proc, &pos));
849:           while (pos) {
850:             PetscInt lid0, ghost_idx, gid1;

852:             PetscCall(PetscCDIntNdGetID(pos, &ghost_idx));
853:             gid1 = lghost_gid[ghost_idx];
854:             PetscCall(PetscCDGetNextPos(ghost_deleted_list, proc, &pos));
855:             PetscCall(PetscCDIntNdGetID(pos, &lid0));
856:             PetscCall(PetscCDGetNextPos(ghost_deleted_list, proc, &pos));
857:             *pt++ = gid1;
858:             *pt++ = lid0 + Istart; // gid0
859:           }
860:           PetscCheck(pt - sbuff == scount, PETSC_COMM_SELF, PETSC_ERR_SUP, "sbuff-pt != scount: %zu", pt - sbuff);
861:           /* MPIU_Isend:  tag1 [ndel, proc, n*[gid1,gid0] ] */
862:           PetscCallMPI(MPIU_Isend(sbuff, scount, MPIU_INT, proc, tag1, comm, request));
863:           PetscCall(PetscCDRemoveAllAt(ghost_deleted_list, proc)); // done with this list
864:         }
865:         /* receive deleted, send back partial aggregates, clear lists */
866:         for (PetscInt proc_idx = 0; proc_idx < ncomm_procs; proc_idx++) {
867:           PetscCallMPI(MPI_Probe(comm_procs[proc_idx] /* MPI_ANY_SOURCE */, tag1, comm, &status));
868:           {
869:             PetscInt         *pt, *pt2, *pt3, *sbuff, tmp;
870:             MPI_Request      *request;
871:             PetscMPIInt       rcount, scount;
872:             const PetscMPIInt proc = status.MPI_SOURCE;

874:             PetscCallMPI(MPI_Get_count(&status, MPIU_INT, &rcount));
875:             if (rcount > rbuff_sz) {
876:               if (rbuff) PetscCall(PetscFree(rbuff));
877:               PetscCall(PetscMalloc1(rcount, &rbuff));
878:               rbuff_sz = rcount;
879:             }
880:             /* MPI_Recv: tag1 [ndel, proc, ndel*[gid1,gid0] ] */
881:             PetscCallMPI(MPI_Recv(rbuff, rcount, MPIU_INT, proc, tag1, comm, &status));
882:             /* read and count sends *[lid0, n, n*[gid] ] */
883:             pt     = rbuff;
884:             scount = 0;
885:             ndel   = *pt++; // number of deleted to recv
886:             tmp    = *pt++; // proc (not used)
887:             while (ndel--) {
888:               PetscInt gid1 = *pt++, lid1 = gid1 - Istart;
889:               PetscInt gh_gid0 = *pt++; // gid on other proc (not used here to count)

891:               PetscCheck(lid1 >= 0 && lid1 < nloc, PETSC_COMM_SELF, PETSC_ERR_SUP, "received ghost deleted %" PetscInt_FMT, gid1);
892:               PetscCheck(!lid_matched[lid1], PETSC_COMM_SELF, PETSC_ERR_PLIB, "%" PetscInt_FMT ") received matched local gid %" PetscInt_FMT ",%" PetscInt_FMT ", with ghost (lid) %" PetscInt_FMT " from proc %d", sub_it, gid1, gh_gid0, tmp, proc);
893:               lid_matched[lid1] = PETSC_TRUE;                    /* keep track of what we've done this round */
894:               PetscCall(PetscCDCountAt(agg_llists, lid1, &tmp)); // n
895:               scount += tmp + 2;                                 // lid0, n, n*[gid]
896:             }
897:             PetscCheck((pt - rbuff) == (ptrdiff_t)rcount, PETSC_COMM_SELF, PETSC_ERR_SUP, "receive buffer size != num read: %zu; rcount: %d", pt - rbuff, rcount);
898:             /* send tag2: *[gid0, n, n*[gid] ] */
899:             PetscCall(PetscMalloc1(scount + request_size, &sbuff));
900:             sbuffs2[proc_idx] = sbuff; /* cache request */
901:             request           = (MPI_Request *)sbuff;
902:             pt2 = sbuff = sbuff + request_size;
903:             // read again: n, proc, n*[gid1,gid0]
904:             pt   = rbuff;
905:             ndel = *pt++;
906:             tmp  = *pt++; // proc (not used)
907:             while (ndel--) {
908:               PetscInt gid1 = *pt++, lid1 = gid1 - Istart, gh_gid0 = *pt++;

910:               /* write [gid0, aggSz, aggSz[gid] ] */
911:               *pt2++ = gh_gid0;
912:               pt3    = pt2++; /* save pointer for later */
913:               PetscCall(PetscCDGetHeadPos(agg_llists, lid1, &pos));
914:               while (pos) {
915:                 PetscInt gid;

917:                 PetscCall(PetscCDIntNdGetID(pos, &gid));
918:                 PetscCall(PetscCDGetNextPos(agg_llists, lid1, &pos));
919:                 *pt2++ = gid;
920:               }
921:               PetscCall(PetscIntCast(pt2 - pt3 - 1, pt3));
922:               /* clear list */
923:               PetscCall(PetscCDRemoveAllAt(agg_llists, lid1));
924:             }
925:             PetscCheck((pt2 - sbuff) == (ptrdiff_t)scount, PETSC_COMM_SELF, PETSC_ERR_SUP, "buffer size != num write: %zu %d", pt2 - sbuff, scount);
926:             /* MPIU_Isend: requested data tag2 *[lid0, n, n*[gid1] ] */
927:             PetscCallMPI(MPIU_Isend(sbuff, scount, MPIU_INT, proc, tag2, comm, request));
928:           }
929:         } // proc_idx
930:         /* receive tag2 *[gid0, n, n*[gid] ] */
931:         for (PetscMPIInt proc_idx = 0; proc_idx < ncomm_procs; proc_idx++) {
932:           PetscMPIInt proc;
933:           PetscInt   *pt;
934:           int         rcount;

936:           PetscCallMPI(MPI_Probe(comm_procs[proc_idx] /* MPI_ANY_SOURCE */, tag2, comm, &status));
937:           PetscCallMPI(MPI_Get_count(&status, MPIU_INT, &rcount));
938:           if (rcount > rbuff_sz) {
939:             if (rbuff) PetscCall(PetscFree(rbuff));
940:             PetscCall(PetscMalloc1(rcount, &rbuff));
941:             rbuff_sz = rcount;
942:           }
943:           proc = status.MPI_SOURCE;
944:           /* MPI_Recv:  tag1 [n, proc, n*[gid1,lid0] ] */
945:           PetscCallMPI(MPI_Recv(rbuff, rcount, MPIU_INT, proc, tag2, comm, &status));
946:           pt = rbuff;
947:           while (pt - rbuff < rcount) {
948:             PetscInt gid0 = *pt++, n = *pt++;

950:             while (n--) {
951:               PetscInt gid1 = *pt++;

953:               PetscCall(PetscCDAppendID(agg_llists, gid0 - Istart, gid1));
954:             }
955:           }
956:           PetscCheck((pt - rbuff) == (ptrdiff_t)rcount, PETSC_COMM_SELF, PETSC_ERR_SUP, "recv buffer size != num read: %zu %d", pt - rbuff, rcount);
957:         }
958:         /* wait for tag1 isends */
959:         for (PetscMPIInt proc_idx = 0; proc_idx < ncomm_procs; proc_idx++) {
960:           MPI_Request *request = (MPI_Request *)sbuffs1[proc_idx];

962:           PetscCallMPI(MPI_Wait(request, &status));
963:           PetscCall(PetscFree(sbuffs1[proc_idx]));
964:         }
965:         /* wait for tag2 isends */
966:         for (PetscMPIInt proc_idx = 0; proc_idx < ncomm_procs; proc_idx++) {
967:           MPI_Request *request = (MPI_Request *)sbuffs2[proc_idx];

969:           PetscCallMPI(MPI_Wait(request, &status));
970:           PetscCall(PetscFree(sbuffs2[proc_idx]));
971:         }
972:       } /* MPI */
973:       /* set 'lghost_matched' - use locMaxEdge, ghostMaxEdge (recomputed next) */
974:       if (isMPI) {
975:         const PetscScalar *sbuff;

977:         for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) {
978:           PetscScalar vval = lid_matched[kk] ? 1.0 : 0.0;

980:           PetscCall(VecSetValues(locMaxEdge, 1, &gid, &vval, INSERT_VALUES)); /* set with GID */
981:         }
982:         PetscCall(VecAssemblyBegin(locMaxEdge));
983:         PetscCall(VecAssemblyEnd(locMaxEdge));
984:         PetscCall(VecScatterBegin(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));
985:         PetscCall(VecScatterEnd(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));
986:         PetscCall(VecGetArrayRead(ghostMaxEdge, &sbuff));
987:         for (PetscInt kk = 0; kk < num_ghosts; kk++) { lghost_matched[kk] = (PetscBool)(PetscRealPart(sbuff[kk]) != 0.0); }
988:         PetscCall(VecRestoreArrayRead(ghostMaxEdge, &sbuff));
989:       }
990:       /* compute 'locMaxEdge' inside sub iteration b/c max weight can drop as neighbors are matched */
991:       for (PetscInt kk = 0, gid = Istart; kk < nloc; kk++, gid++) {
992:         PetscReal      max_e = 0., tt;
993:         PetscScalar    vval;
994:         const PetscInt lid    = kk;
995:         PetscMPIInt    max_pe = rank, pe, n;

997:         ii = matA->i;
998:         PetscCall(PetscMPIIntCast(ii[lid + 1] - ii[lid], &n));
999:         aj = PetscSafePointerPlusOffset(matA->j, ii[lid]);
1000:         ap = PetscSafePointerPlusOffset(matA->a, ii[lid]);
1001:         for (PetscMPIInt jj = 0; jj < n; jj++) {
1002:           PetscInt lidj = aj[jj];

1004:           if (lid_matched[lidj]) continue; /* this is new - can change local max */
1005:           if (lidj != lid && PetscRealPart(ap[jj]) > max_e) max_e = PetscRealPart(ap[jj]);
1006:         }
1007:         if (lid_cprowID && (ix = lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
1008:           ii = matB->compressedrow.i;
1009:           PetscCall(PetscMPIIntCast(ii[ix + 1] - ii[ix], &n));
1010:           ap = matB->a + ii[ix];
1011:           aj = matB->j + ii[ix];
1012:           for (PetscMPIInt jj = 0; jj < n; jj++) {
1013:             PetscInt lidj = aj[jj];

1015:             if (lghost_matched[lidj]) continue;
1016:             if ((tt = PetscRealPart(ap[jj])) > max_e) max_e = tt;
1017:           }
1018:         }
1019:         vval = max_e;
1020:         PetscCall(VecSetValues(locMaxEdge, 1, &gid, &vval, INSERT_VALUES)); /* set with GID */
1021:         // max PE with max edge
1022:         if (lid_cprowID && (ix = lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
1023:           ii = matB->compressedrow.i;
1024:           PetscCall(PetscMPIIntCast(ii[ix + 1] - ii[ix], &n));
1025:           ap = matB->a + ii[ix];
1026:           aj = matB->j + ii[ix];
1027:           for (PetscInt jj = 0; jj < n; jj++) {
1028:             PetscInt lidj = aj[jj];

1030:             if (lghost_matched[lidj]) continue;
1031:             if ((pe = lghost_pe[aj[jj]]) > max_pe && PetscRealPart(ap[jj]) >= max_e - MY_MEPS) { max_pe = pe; }
1032:           }
1033:         }
1034:         vval = max_pe;
1035:         PetscCall(VecSetValues(locMaxPE, 1, &gid, &vval, INSERT_VALUES));
1036:       }
1037:       PetscCall(VecAssemblyBegin(locMaxEdge));
1038:       PetscCall(VecAssemblyEnd(locMaxEdge));
1039:       PetscCall(VecAssemblyBegin(locMaxPE));
1040:       PetscCall(VecAssemblyEnd(locMaxPE));
1041:       /* compute 'lghost_max_ew' and 'lghost_max_pe' to get ready for next iteration*/
1042:       if (isMPI) {
1043:         const PetscScalar *buf;

1045:         PetscCall(VecScatterBegin(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));
1046:         PetscCall(VecScatterEnd(mpimat->Mvctx, locMaxEdge, ghostMaxEdge, INSERT_VALUES, SCATTER_FORWARD));
1047:         PetscCall(VecScatterBegin(mpimat->Mvctx, locMaxPE, ghostMaxPE, INSERT_VALUES, SCATTER_FORWARD));
1048:         PetscCall(VecScatterEnd(mpimat->Mvctx, locMaxPE, ghostMaxPE, INSERT_VALUES, SCATTER_FORWARD));
1049:         PetscCall(VecGetArrayRead(ghostMaxPE, &buf));
1050:         for (PetscInt kk = 0; kk < num_ghosts; kk++) {
1051:           lghost_max_pe[kk] = (PetscMPIInt)PetscRealPart(buf[kk]); // the MAX proc of the ghost now
1052:         }
1053:         PetscCall(VecRestoreArrayRead(ghostMaxPE, &buf));
1054:       }
1055:       // if no active edges, stop
1056:       if (gn_act_n[0] < 1) break;
1057:       // inc and check (self stopping iteration
1058:       PetscCheck(old_num_edge != gn_act_n[0], PETSC_COMM_SELF, PETSC_ERR_SUP, "HEM stalled step %" PetscInt_FMT "/%" PetscInt_FMT, sub_it + 1, n_sub_its);
1059:       sub_it++;
1060:       PetscCheck(sub_it < n_sub_its, PETSC_COMM_SELF, PETSC_ERR_SUP, "failed to finish HEM step %" PetscInt_FMT "/%" PetscInt_FMT, sub_it + 1, n_sub_its);
1061:       old_num_edge = gn_act_n[0];
1062:     } /* sub_it loop */
1063:     /* clean up iteration */
1064:     PetscCall(PetscFree(Edges));
1065:     if (isMPI) { // can be hoisted
1066:       PetscCall(VecRestoreArrayRead(ghostMaxEdge, &lghost_max_ew));
1067:       PetscCall(VecDestroy(&ghostMaxEdge));
1068:       PetscCall(VecDestroy(&ghostMaxPE));
1069:       PetscCall(PetscFree4(lghost_matched, lghost_pe, lghost_gid, lghost_max_pe));
1070:     }
1071:     PetscCall(VecDestroy(&locMaxEdge));
1072:     PetscCall(VecDestroy(&locMaxPE));
1073:     /* create next graph */
1074:     {
1075:       Vec diag;

1077:       /* add identity for unmatched vertices so they stay alive */
1078:       for (PetscInt kk = 0, gid1, gid = Istart; kk < nloc; kk++, gid++) {
1079:         if (!lid_matched[kk]) {
1080:           const PetscInt lid = kk;
1081:           PetscCDIntNd  *pos;

1083:           PetscCall(PetscCDGetHeadPos(agg_llists, lid, &pos));
1084:           PetscCheck(pos, PETSC_COMM_SELF, PETSC_ERR_PLIB, "empty list in singleton: %" PetscInt_FMT, gid);
1085:           PetscCall(PetscCDIntNdGetID(pos, &gid1));
1086:           PetscCheck(gid1 == gid, PETSC_COMM_SELF, PETSC_ERR_PLIB, "first in list (%" PetscInt_FMT ") in singleton not %" PetscInt_FMT, gid1, gid);
1087:           PetscCall(MatSetValues(P, 1, &gid, 1, &gid, &one, INSERT_VALUES));
1088:         }
1089:       }
1090:       PetscCall(MatAssemblyBegin(P, MAT_FINAL_ASSEMBLY));
1091:       PetscCall(MatAssemblyEnd(P, MAT_FINAL_ASSEMBLY));

1093:       /* project to make new graph with collapsed edges */
1094:       PetscCall(MatPtAP(cMat, P, MAT_INITIAL_MATRIX, 1.0, &tMat));
1095:       PetscCall(MatDestroy(&P));
1096:       PetscCall(MatDestroy(&cMat));
1097:       cMat = tMat;
1098:       PetscCall(MatCreateVecs(cMat, &diag, NULL));
1099:       PetscCall(MatGetDiagonal(cMat, diag));
1100:       PetscCall(VecReciprocal(diag));
1101:       PetscCall(VecSqrtAbs(diag));
1102:       PetscCall(MatDiagonalScale(cMat, diag, diag));
1103:       PetscCall(VecDestroy(&diag));
1104:     }
1105:   } /* coarsen iterator */

1107:   /* make fake matrix with Mat->B only for smoothed agg QR. Need this if we make an aux graph (ie, PtAP) with k > 1 */
1108:   if (size > 1) {
1109:     Mat           mat;
1110:     PetscCDIntNd *pos;
1111:     PetscInt      NN, MM, jj = 0, mxsz = 0;

1113:     for (PetscInt kk = 0; kk < nloc; kk++) {
1114:       PetscCall(PetscCDCountAt(agg_llists, kk, &jj));
1115:       if (jj > mxsz) mxsz = jj;
1116:     }
1117:     PetscCall(MatGetSize(a_Gmat, &MM, &NN));
1118:     if (mxsz > MM - nloc) mxsz = MM - nloc;
1119:     /* matrix of ghost adj for square graph */
1120:     PetscCall(MatCreateAIJ(comm, nloc, nloc, PETSC_DETERMINE, PETSC_DETERMINE, 0, NULL, mxsz, NULL, &mat));
1121:     for (PetscInt lid = 0, gid = Istart; lid < nloc; lid++, gid++) {
1122:       PetscCall(PetscCDGetHeadPos(agg_llists, lid, &pos));
1123:       while (pos) {
1124:         PetscInt gid1;

1126:         PetscCall(PetscCDIntNdGetID(pos, &gid1));
1127:         PetscCall(PetscCDGetNextPos(agg_llists, lid, &pos));
1128:         if (gid1 < Istart || gid1 >= Istart + nloc) PetscCall(MatSetValues(mat, 1, &gid, 1, &gid1, &one, ADD_VALUES));
1129:       }
1130:     }
1131:     PetscCall(MatAssemblyBegin(mat, MAT_FINAL_ASSEMBLY));
1132:     PetscCall(MatAssemblyEnd(mat, MAT_FINAL_ASSEMBLY));
1133:     PetscCall(PetscCDSetMat(agg_llists, mat));
1134:     PetscCall(PetscCDDestroy(ghost_deleted_list));
1135:     if (rbuff_sz) PetscCall(PetscFree(rbuff)); // always true
1136:   }
1137:   // move BCs into some node
1138:   if (bc_list) {
1139:     PetscCDIntNd *pos;

1141:     PetscCall(PetscCDGetHeadPos(bc_list, 0, &pos));
1142:     while (pos) {
1143:       PetscInt gid1;

1145:       PetscCall(PetscCDIntNdGetID(pos, &gid1));
1146:       PetscCall(PetscCDGetNextPos(bc_list, 0, &pos));
1147:       PetscCall(PetscCDAppendID(agg_llists, bc_agg, gid1));
1148:     }
1149:     PetscCall(PetscCDRemoveAllAt(bc_list, 0));
1150:     PetscCall(PetscCDDestroy(bc_list));
1151:   }
1152:   {
1153:     // check sizes -- all vertices must get in graph
1154:     PetscInt sz, globalsz, MM;

1156:     PetscCall(MatGetSize(a_Gmat, &MM, NULL));
1157:     PetscCall(PetscCDCount(agg_llists, &sz));
1158:     PetscCallMPI(MPIU_Allreduce(&sz, &globalsz, 1, MPIU_INT, MPI_SUM, comm));
1159:     PetscCheck(MM == globalsz, comm, PETSC_ERR_SUP, "lost %" PetscInt_FMT " equations ?", MM - globalsz);
1160:   }
1161:   // cleanup
1162:   PetscCall(MatDestroy(&cMat));
1163:   PetscCall(PetscFree3(lid_matched, lid_cprowID, lid_max_pe));
1164:   PetscCall(ISDestroy(&info_is));
1165:   PetscFunctionReturn(PETSC_SUCCESS);
1166: }

1168: /*
1169:    HEM coarsen, simple greedy.
1170: */
1171: static PetscErrorCode MatCoarsenApply_HEM(MatCoarsen coarse)
1172: {
1173:   Mat mat = coarse->graph;

1175:   PetscFunctionBegin;
1176:   PetscCall(MatCoarsenApply_HEM_private(mat, coarse->max_it, coarse->threshold, &coarse->agg_lists));
1177:   PetscFunctionReturn(PETSC_SUCCESS);
1178: }

1180: static PetscErrorCode MatCoarsenView_HEM(MatCoarsen coarse, PetscViewer viewer)
1181: {
1182:   PetscMPIInt rank;
1183:   PetscBool   iascii;

1185:   PetscFunctionBegin;
1186:   PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)coarse), &rank));
1187:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
1188:   if (iascii) {
1189:     PetscCDIntNd     *pos, *pos2;
1190:     PetscViewerFormat format;

1192:     PetscCall(PetscViewerASCIIPrintf(viewer, "%" PetscInt_FMT " matching steps with threshold = %g\n", coarse->max_it, (double)coarse->threshold));
1193:     PetscCall(PetscViewerGetFormat(viewer, &format));
1194:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
1195:       if (coarse->agg_lists) {
1196:         PetscCall(PetscViewerASCIIPushSynchronized(viewer));
1197:         for (PetscInt kk = 0; kk < coarse->agg_lists->size; kk++) {
1198:           PetscCall(PetscCDGetHeadPos(coarse->agg_lists, kk, &pos));
1199:           if ((pos2 = pos)) PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, "selected local %" PetscInt_FMT ": ", kk));
1200:           while (pos) {
1201:             PetscInt gid1;

1203:             PetscCall(PetscCDIntNdGetID(pos, &gid1));
1204:             PetscCall(PetscCDGetNextPos(coarse->agg_lists, kk, &pos));
1205:             PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, " %" PetscInt_FMT " ", gid1));
1206:           }
1207:           if (pos2) PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, "\n"));
1208:         }
1209:         PetscCall(PetscViewerFlush(viewer));
1210:         PetscCall(PetscViewerASCIIPopSynchronized(viewer));
1211:       } else {
1212:         PetscCall(PetscViewerASCIIPrintf(viewer, "  HEM aggregator lists are not available\n"));
1213:       }
1214:     }
1215:   }
1216:   PetscFunctionReturn(PETSC_SUCCESS);
1217: }

1219: /*MC
1220:    MATCOARSENHEM - A coarsener that uses HEM a simple greedy coarsener

1222:    Level: beginner

1224: .seealso: `MatCoarsen`, `MatCoarsenMISKSetDistance()`, `MatCoarsenApply()`, `MatCoarsenSetType()`, `MatCoarsenType`, `MatCoarsenCreate()`, `MATCOARSENMISK`, `MATCOARSENMIS`
1225: M*/

1227: PETSC_EXTERN PetscErrorCode MatCoarsenCreate_HEM(MatCoarsen coarse)
1228: {
1229:   PetscFunctionBegin;
1230:   coarse->ops->apply = MatCoarsenApply_HEM;
1231:   coarse->ops->view  = MatCoarsenView_HEM;
1232:   coarse->max_it     = 4;
1233:   PetscFunctionReturn(PETSC_SUCCESS);
1234: }