xref: /petsc/src/mat/impls/adj/mpi/mpiadj.c (revision a96705020bd7e362116d3e2c8daa1efc28dedc1e)
1 /*
2     Defines the basic matrix operations for the ADJ adjacency list matrix data-structure.
3 */
4 #include <../src/mat/impls/adj/mpi/mpiadj.h> /*I "petscmat.h" I*/
5 #include <petscsf.h>
6 
7 /*
8   The interface should be easy to use for both MatCreateSubMatrix (parallel sub-matrix) and MatCreateSubMatrices (sequential sub-matrices)
9 */
10 static PetscErrorCode MatCreateSubMatrix_MPIAdj_data(Mat adj, IS irows, IS icols, PetscInt **sadj_xadj, PetscInt **sadj_adjncy, PetscInt **sadj_values)
11 {
12   PetscInt        nlrows_is, icols_n, i, j, nroots, nleaves, rlocalindex, *ncols_send, *ncols_recv;
13   PetscInt        nlrows_mat, *adjncy_recv, Ncols_recv, Ncols_send, *xadj_recv, *values_recv;
14   PetscInt       *ncols_recv_offsets, loc, rnclos, *sadjncy, *sxadj, *svalues;
15   const PetscInt *irows_indices, *icols_indices, *xadj, *adjncy;
16   PetscMPIInt     owner;
17   Mat_MPIAdj     *a = (Mat_MPIAdj *)adj->data;
18   PetscLayout     rmap;
19   MPI_Comm        comm;
20   PetscSF         sf;
21   PetscSFNode    *iremote;
22   PetscBool       done;
23 
24   PetscFunctionBegin;
25   PetscCall(PetscObjectGetComm((PetscObject)adj, &comm));
26   PetscCall(MatGetLayouts(adj, &rmap, NULL));
27   PetscCall(ISGetLocalSize(irows, &nlrows_is));
28   PetscCall(ISGetIndices(irows, &irows_indices));
29   PetscCall(PetscMalloc1(nlrows_is, &iremote));
30   /* construct sf graph*/
31   nleaves = nlrows_is;
32   for (i = 0; i < nlrows_is; i++) {
33     owner       = -1;
34     rlocalindex = -1;
35     PetscCall(PetscLayoutFindOwnerIndex(rmap, irows_indices[i], &owner, &rlocalindex));
36     iremote[i].rank  = owner;
37     iremote[i].index = rlocalindex;
38   }
39   PetscCall(MatGetRowIJ(adj, 0, PETSC_FALSE, PETSC_FALSE, &nlrows_mat, &xadj, &adjncy, &done));
40   PetscCall(PetscCalloc4(nlrows_mat, &ncols_send, nlrows_is, &xadj_recv, nlrows_is + 1, &ncols_recv_offsets, nlrows_is, &ncols_recv));
41   nroots = nlrows_mat;
42   for (i = 0; i < nlrows_mat; i++) ncols_send[i] = xadj[i + 1] - xadj[i];
43   PetscCall(PetscSFCreate(comm, &sf));
44   PetscCall(PetscSFSetGraph(sf, nroots, nleaves, NULL, PETSC_OWN_POINTER, iremote, PETSC_OWN_POINTER));
45   PetscCall(PetscSFSetType(sf, PETSCSFBASIC));
46   PetscCall(PetscSFSetFromOptions(sf));
47   PetscCall(PetscSFBcastBegin(sf, MPIU_INT, ncols_send, ncols_recv, MPI_REPLACE));
48   PetscCall(PetscSFBcastEnd(sf, MPIU_INT, ncols_send, ncols_recv, MPI_REPLACE));
49   PetscCall(PetscSFBcastBegin(sf, MPIU_INT, xadj, xadj_recv, MPI_REPLACE));
50   PetscCall(PetscSFBcastEnd(sf, MPIU_INT, xadj, xadj_recv, MPI_REPLACE));
51   PetscCall(PetscSFDestroy(&sf));
52   Ncols_recv = 0;
53   for (i = 0; i < nlrows_is; i++) {
54     Ncols_recv += ncols_recv[i];
55     ncols_recv_offsets[i + 1] = ncols_recv[i] + ncols_recv_offsets[i];
56   }
57   Ncols_send = 0;
58   for (i = 0; i < nlrows_mat; i++) Ncols_send += ncols_send[i];
59   PetscCall(PetscCalloc1(Ncols_recv, &iremote));
60   PetscCall(PetscCalloc1(Ncols_recv, &adjncy_recv));
61   nleaves    = Ncols_recv;
62   Ncols_recv = 0;
63   for (i = 0; i < nlrows_is; i++) {
64     PetscCall(PetscLayoutFindOwner(rmap, irows_indices[i], &owner));
65     for (j = 0; j < ncols_recv[i]; j++) {
66       iremote[Ncols_recv].rank    = owner;
67       iremote[Ncols_recv++].index = xadj_recv[i] + j;
68     }
69   }
70   PetscCall(ISRestoreIndices(irows, &irows_indices));
71   /*if we need to deal with edge weights ???*/
72   if (a->useedgeweights) PetscCall(PetscCalloc1(Ncols_recv, &values_recv));
73   nroots = Ncols_send;
74   PetscCall(PetscSFCreate(comm, &sf));
75   PetscCall(PetscSFSetGraph(sf, nroots, nleaves, NULL, PETSC_OWN_POINTER, iremote, PETSC_OWN_POINTER));
76   PetscCall(PetscSFSetType(sf, PETSCSFBASIC));
77   PetscCall(PetscSFSetFromOptions(sf));
78   PetscCall(PetscSFBcastBegin(sf, MPIU_INT, adjncy, adjncy_recv, MPI_REPLACE));
79   PetscCall(PetscSFBcastEnd(sf, MPIU_INT, adjncy, adjncy_recv, MPI_REPLACE));
80   if (a->useedgeweights) {
81     PetscCall(PetscSFBcastBegin(sf, MPIU_INT, a->values, values_recv, MPI_REPLACE));
82     PetscCall(PetscSFBcastEnd(sf, MPIU_INT, a->values, values_recv, MPI_REPLACE));
83   }
84   PetscCall(PetscSFDestroy(&sf));
85   PetscCall(MatRestoreRowIJ(adj, 0, PETSC_FALSE, PETSC_FALSE, &nlrows_mat, &xadj, &adjncy, &done));
86   PetscCall(ISGetLocalSize(icols, &icols_n));
87   PetscCall(ISGetIndices(icols, &icols_indices));
88   rnclos = 0;
89   for (i = 0; i < nlrows_is; i++) {
90     for (j = ncols_recv_offsets[i]; j < ncols_recv_offsets[i + 1]; j++) {
91       PetscCall(PetscFindInt(adjncy_recv[j], icols_n, icols_indices, &loc));
92       if (loc < 0) {
93         adjncy_recv[j] = -1;
94         if (a->useedgeweights) values_recv[j] = -1;
95         ncols_recv[i]--;
96       } else {
97         rnclos++;
98       }
99     }
100   }
101   PetscCall(ISRestoreIndices(icols, &icols_indices));
102   PetscCall(PetscCalloc1(rnclos, &sadjncy));
103   if (a->useedgeweights) PetscCall(PetscCalloc1(rnclos, &svalues));
104   PetscCall(PetscCalloc1(nlrows_is + 1, &sxadj));
105   rnclos = 0;
106   for (i = 0; i < nlrows_is; i++) {
107     for (j = ncols_recv_offsets[i]; j < ncols_recv_offsets[i + 1]; j++) {
108       if (adjncy_recv[j] < 0) continue;
109       sadjncy[rnclos] = adjncy_recv[j];
110       if (a->useedgeweights) svalues[rnclos] = values_recv[j];
111       rnclos++;
112     }
113   }
114   for (i = 0; i < nlrows_is; i++) sxadj[i + 1] = sxadj[i] + ncols_recv[i];
115   if (sadj_xadj) {
116     *sadj_xadj = sxadj;
117   } else PetscCall(PetscFree(sxadj));
118   if (sadj_adjncy) {
119     *sadj_adjncy = sadjncy;
120   } else PetscCall(PetscFree(sadjncy));
121   if (sadj_values) {
122     if (a->useedgeweights) *sadj_values = svalues;
123     else *sadj_values = NULL;
124   } else {
125     if (a->useedgeweights) PetscCall(PetscFree(svalues));
126   }
127   PetscCall(PetscFree4(ncols_send, xadj_recv, ncols_recv_offsets, ncols_recv));
128   PetscCall(PetscFree(adjncy_recv));
129   if (a->useedgeweights) PetscCall(PetscFree(values_recv));
130   PetscFunctionReturn(PETSC_SUCCESS);
131 }
132 
133 static PetscErrorCode MatCreateSubMatrices_MPIAdj_Private(Mat mat, PetscInt n, const IS irow[], const IS icol[], PetscBool subcomm, MatReuse scall, Mat *submat[])
134 {
135   PetscInt        i, irow_n, icol_n, *sxadj, *sadjncy, *svalues;
136   PetscInt       *indices, nindx, j, k, loc;
137   PetscMPIInt     issame;
138   const PetscInt *irow_indices, *icol_indices;
139   MPI_Comm        scomm_row, scomm_col, scomm_mat;
140 
141   PetscFunctionBegin;
142   nindx = 0;
143   /*
144    * Estimate a maximum number for allocating memory
145    */
146   for (i = 0; i < n; i++) {
147     PetscCall(ISGetLocalSize(irow[i], &irow_n));
148     PetscCall(ISGetLocalSize(icol[i], &icol_n));
149     nindx = nindx > (irow_n + icol_n) ? nindx : (irow_n + icol_n);
150   }
151   PetscCall(PetscMalloc1(nindx, &indices));
152   /* construct a submat */
153   //  if (scall == MAT_INITIAL_MATRIX) PetscCall(PetscMalloc1(n,submat));
154 
155   for (i = 0; i < n; i++) {
156     if (subcomm) {
157       PetscCall(PetscObjectGetComm((PetscObject)irow[i], &scomm_row));
158       PetscCall(PetscObjectGetComm((PetscObject)icol[i], &scomm_col));
159       PetscCallMPI(MPI_Comm_compare(scomm_row, scomm_col, &issame));
160       PetscCheck(issame == MPI_IDENT, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "row index set must have the same comm as the col index set");
161       PetscCallMPI(MPI_Comm_compare(scomm_row, PETSC_COMM_SELF, &issame));
162       PetscCheck(issame != MPI_IDENT, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, " can not use PETSC_COMM_SELF as comm when extracting a parallel submatrix");
163     } else {
164       scomm_row = PETSC_COMM_SELF;
165     }
166     /*get sub-matrix data*/
167     sxadj   = NULL;
168     sadjncy = NULL;
169     svalues = NULL;
170     PetscCall(MatCreateSubMatrix_MPIAdj_data(mat, irow[i], icol[i], &sxadj, &sadjncy, &svalues));
171     PetscCall(ISGetLocalSize(irow[i], &irow_n));
172     PetscCall(ISGetLocalSize(icol[i], &icol_n));
173     PetscCall(ISGetIndices(irow[i], &irow_indices));
174     PetscCall(PetscArraycpy(indices, irow_indices, irow_n));
175     PetscCall(ISRestoreIndices(irow[i], &irow_indices));
176     PetscCall(ISGetIndices(icol[i], &icol_indices));
177     PetscCall(PetscArraycpy(indices + irow_n, icol_indices, icol_n));
178     PetscCall(ISRestoreIndices(icol[i], &icol_indices));
179     nindx = irow_n + icol_n;
180     PetscCall(PetscSortRemoveDupsInt(&nindx, indices));
181     /* renumber columns */
182     for (j = 0; j < irow_n; j++) {
183       for (k = sxadj[j]; k < sxadj[j + 1]; k++) {
184         PetscCall(PetscFindInt(sadjncy[k], nindx, indices, &loc));
185         PetscCheck(loc >= 0, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "can not find col %" PetscInt_FMT, sadjncy[k]);
186         sadjncy[k] = loc;
187       }
188     }
189     if (scall == MAT_INITIAL_MATRIX) {
190       PetscCall(MatCreateMPIAdj(scomm_row, irow_n, icol_n, sxadj, sadjncy, svalues, submat[i]));
191     } else {
192       Mat         sadj = *(submat[i]);
193       Mat_MPIAdj *sa   = (Mat_MPIAdj *)((sadj)->data);
194       PetscCall(PetscObjectGetComm((PetscObject)sadj, &scomm_mat));
195       PetscCallMPI(MPI_Comm_compare(scomm_row, scomm_mat, &issame));
196       PetscCheck(issame == MPI_IDENT, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "submatrix  must have the same comm as the col index set");
197       PetscCall(PetscArraycpy(sa->i, sxadj, irow_n + 1));
198       PetscCall(PetscArraycpy(sa->j, sadjncy, sxadj[irow_n]));
199       if (svalues) PetscCall(PetscArraycpy(sa->values, svalues, sxadj[irow_n]));
200       PetscCall(PetscFree(sxadj));
201       PetscCall(PetscFree(sadjncy));
202       PetscCall(PetscFree(svalues));
203     }
204   }
205   PetscCall(PetscFree(indices));
206   PetscFunctionReturn(PETSC_SUCCESS);
207 }
208 
209 static PetscErrorCode MatCreateSubMatricesMPI_MPIAdj(Mat mat, PetscInt n, const IS irow[], const IS icol[], MatReuse scall, Mat *submat[])
210 {
211   /*get sub-matrices across a sub communicator */
212   PetscFunctionBegin;
213   PetscCall(MatCreateSubMatrices_MPIAdj_Private(mat, n, irow, icol, PETSC_TRUE, scall, submat));
214   PetscFunctionReturn(PETSC_SUCCESS);
215 }
216 
217 static PetscErrorCode MatCreateSubMatrices_MPIAdj(Mat mat, PetscInt n, const IS irow[], const IS icol[], MatReuse scall, Mat *submat[])
218 {
219   PetscFunctionBegin;
220   /*get sub-matrices based on PETSC_COMM_SELF */
221   PetscCall(MatCreateSubMatrices_MPIAdj_Private(mat, n, irow, icol, PETSC_FALSE, scall, submat));
222   PetscFunctionReturn(PETSC_SUCCESS);
223 }
224 
225 static PetscErrorCode MatView_MPIAdj_ASCII(Mat A, PetscViewer viewer)
226 {
227   Mat_MPIAdj       *a = (Mat_MPIAdj *)A->data;
228   PetscInt          i, j, m = A->rmap->n;
229   const char       *name;
230   PetscViewerFormat format;
231 
232   PetscFunctionBegin;
233   PetscCall(PetscObjectGetName((PetscObject)A, &name));
234   PetscCall(PetscViewerGetFormat(viewer, &format));
235   if (format == PETSC_VIEWER_ASCII_INFO) {
236     PetscFunctionReturn(PETSC_SUCCESS);
237   } else {
238     PetscCheck(format != PETSC_VIEWER_ASCII_MATLAB, PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "MATLAB format not supported");
239     PetscCall(PetscViewerASCIIUseTabs(viewer, PETSC_FALSE));
240     PetscCall(PetscViewerASCIIPushSynchronized(viewer));
241     for (i = 0; i < m; i++) {
242       PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, "row %" PetscInt_FMT ":", i + A->rmap->rstart));
243       for (j = a->i[i]; j < a->i[i + 1]; j++) {
244         if (a->values) {
245           PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, " (%" PetscInt_FMT ", %" PetscInt_FMT ") ", a->j[j], a->values[j]));
246         } else {
247           PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, " %" PetscInt_FMT " ", a->j[j]));
248         }
249       }
250       PetscCall(PetscViewerASCIISynchronizedPrintf(viewer, "\n"));
251     }
252     PetscCall(PetscViewerASCIIUseTabs(viewer, PETSC_TRUE));
253     PetscCall(PetscViewerFlush(viewer));
254     PetscCall(PetscViewerASCIIPopSynchronized(viewer));
255   }
256   PetscFunctionReturn(PETSC_SUCCESS);
257 }
258 
259 static PetscErrorCode MatView_MPIAdj(Mat A, PetscViewer viewer)
260 {
261   PetscBool iascii;
262 
263   PetscFunctionBegin;
264   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
265   if (iascii) PetscCall(MatView_MPIAdj_ASCII(A, viewer));
266   PetscFunctionReturn(PETSC_SUCCESS);
267 }
268 
269 static PetscErrorCode MatDestroy_MPIAdj(Mat mat)
270 {
271   Mat_MPIAdj *a = (Mat_MPIAdj *)mat->data;
272 
273   PetscFunctionBegin;
274   PetscCall(PetscLogObjectState((PetscObject)mat, "Rows=%" PetscInt_FMT ", Cols=%" PetscInt_FMT ", NZ=%" PetscInt_FMT, mat->rmap->n, mat->cmap->n, a->nz));
275   PetscCall(PetscFree(a->diag));
276   if (a->freeaij) {
277     if (a->freeaijwithfree) {
278       if (a->i) free(a->i);
279       if (a->j) free(a->j);
280     } else {
281       PetscCall(PetscFree(a->i));
282       PetscCall(PetscFree(a->j));
283       PetscCall(PetscFree(a->values));
284     }
285   }
286   PetscCall(PetscFree(a->rowvalues));
287   PetscCall(PetscFree(mat->data));
288   PetscCall(PetscObjectChangeTypeName((PetscObject)mat, NULL));
289   PetscCall(PetscObjectComposeFunction((PetscObject)mat, "MatMPIAdjSetPreallocation_C", NULL));
290   PetscCall(PetscObjectComposeFunction((PetscObject)mat, "MatMPIAdjCreateNonemptySubcommMat_C", NULL));
291   PetscCall(PetscObjectComposeFunction((PetscObject)mat, "MatMPIAdjToSeq_C", NULL));
292   PetscCall(PetscObjectComposeFunction((PetscObject)mat, "MatMPIAdjToSeqRankZero_C", NULL));
293   PetscFunctionReturn(PETSC_SUCCESS);
294 }
295 
296 static PetscErrorCode MatSetOption_MPIAdj(Mat A, MatOption op, PetscBool flg)
297 {
298   Mat_MPIAdj *a = (Mat_MPIAdj *)A->data;
299 
300   PetscFunctionBegin;
301   switch (op) {
302   case MAT_SYMMETRIC:
303   case MAT_STRUCTURALLY_SYMMETRIC:
304   case MAT_HERMITIAN:
305   case MAT_SPD:
306     a->symmetric = flg;
307     break;
308   case MAT_SYMMETRY_ETERNAL:
309   case MAT_STRUCTURAL_SYMMETRY_ETERNAL:
310   case MAT_SPD_ETERNAL:
311     break;
312   default:
313     PetscCall(PetscInfo(A, "Option %s ignored\n", MatOptions[op]));
314     break;
315   }
316   PetscFunctionReturn(PETSC_SUCCESS);
317 }
318 
319 static PetscErrorCode MatGetRow_MPIAdj(Mat A, PetscInt row, PetscInt *nz, PetscInt **idx, PetscScalar **v)
320 {
321   Mat_MPIAdj *a = (Mat_MPIAdj *)A->data;
322 
323   PetscFunctionBegin;
324   row -= A->rmap->rstart;
325   PetscCheck(row >= 0 && row < A->rmap->n, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Row out of range");
326   *nz = a->i[row + 1] - a->i[row];
327   if (v) {
328     PetscInt j;
329     if (a->rowvalues_alloc < *nz) {
330       PetscCall(PetscFree(a->rowvalues));
331       a->rowvalues_alloc = PetscMax(a->rowvalues_alloc * 2, *nz);
332       PetscCall(PetscMalloc1(a->rowvalues_alloc, &a->rowvalues));
333     }
334     for (j = 0; j < *nz; j++) a->rowvalues[j] = a->values ? a->values[a->i[row] + j] : 1.0;
335     *v = (*nz) ? a->rowvalues : NULL;
336   }
337   if (idx) *idx = (*nz) ? a->j + a->i[row] : NULL;
338   PetscFunctionReturn(PETSC_SUCCESS);
339 }
340 
341 static PetscErrorCode MatRestoreRow_MPIAdj(Mat A, PetscInt row, PetscInt *nz, PetscInt **idx, PetscScalar **v)
342 {
343   PetscFunctionBegin;
344   PetscFunctionReturn(PETSC_SUCCESS);
345 }
346 
347 static PetscErrorCode MatEqual_MPIAdj(Mat A, Mat B, PetscBool *flg)
348 {
349   Mat_MPIAdj *a = (Mat_MPIAdj *)A->data, *b = (Mat_MPIAdj *)B->data;
350   PetscBool   flag;
351 
352   PetscFunctionBegin;
353   /* If the  matrix dimensions are not equal,or no of nonzeros */
354   if ((A->rmap->n != B->rmap->n) || (a->nz != b->nz)) flag = PETSC_FALSE;
355 
356   /* if the a->i are the same */
357   PetscCall(PetscArraycmp(a->i, b->i, A->rmap->n + 1, &flag));
358 
359   /* if a->j are the same */
360   PetscCall(PetscMemcmp(a->j, b->j, (a->nz) * sizeof(PetscInt), &flag));
361 
362   PetscCall(MPIU_Allreduce(&flag, flg, 1, MPIU_BOOL, MPI_LAND, PetscObjectComm((PetscObject)A)));
363   PetscFunctionReturn(PETSC_SUCCESS);
364 }
365 
366 static PetscErrorCode MatGetRowIJ_MPIAdj(Mat A, PetscInt oshift, PetscBool symmetric, PetscBool blockcompressed, PetscInt *m, const PetscInt *inia[], const PetscInt *inja[], PetscBool *done)
367 {
368   PetscInt    i;
369   Mat_MPIAdj *a  = (Mat_MPIAdj *)A->data;
370   PetscInt  **ia = (PetscInt **)inia, **ja = (PetscInt **)inja;
371 
372   PetscFunctionBegin;
373   *m    = A->rmap->n;
374   *ia   = a->i;
375   *ja   = a->j;
376   *done = PETSC_TRUE;
377   if (oshift) {
378     for (i = 0; i < (*ia)[*m]; i++) (*ja)[i]++;
379     for (i = 0; i <= (*m); i++) (*ia)[i]++;
380   }
381   PetscFunctionReturn(PETSC_SUCCESS);
382 }
383 
384 static PetscErrorCode MatRestoreRowIJ_MPIAdj(Mat A, PetscInt oshift, PetscBool symmetric, PetscBool blockcompressed, PetscInt *m, const PetscInt *inia[], const PetscInt *inja[], PetscBool *done)
385 {
386   PetscInt    i;
387   Mat_MPIAdj *a  = (Mat_MPIAdj *)A->data;
388   PetscInt  **ia = (PetscInt **)inia, **ja = (PetscInt **)inja;
389 
390   PetscFunctionBegin;
391   PetscCheck(!ia || a->i == *ia, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_WRONGSTATE, "ia passed back is not one obtained with MatGetRowIJ()");
392   PetscCheck(!ja || a->j == *ja, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_WRONGSTATE, "ja passed back is not one obtained with MatGetRowIJ()");
393   if (oshift) {
394     PetscCheck(ia, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_WRONGSTATE, "If oshift then you must passed in inia[] argument");
395     PetscCheck(ja, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_WRONGSTATE, "If oshift then you must passed in inja[] argument");
396     for (i = 0; i <= (*m); i++) (*ia)[i]--;
397     for (i = 0; i < (*ia)[*m]; i++) (*ja)[i]--;
398   }
399   PetscFunctionReturn(PETSC_SUCCESS);
400 }
401 
402 static PetscErrorCode MatConvertFrom_MPIAdj(Mat A, MatType type, MatReuse reuse, Mat *newmat)
403 {
404   Mat                B;
405   PetscInt           i, m, N, nzeros = 0, *ia, *ja, len, rstart, cnt, j, *a;
406   const PetscInt    *rj;
407   const PetscScalar *ra;
408   MPI_Comm           comm;
409 
410   PetscFunctionBegin;
411   PetscCall(MatGetSize(A, NULL, &N));
412   PetscCall(MatGetLocalSize(A, &m, NULL));
413   PetscCall(MatGetOwnershipRange(A, &rstart, NULL));
414 
415   /* count the number of nonzeros per row */
416   for (i = 0; i < m; i++) {
417     PetscCall(MatGetRow(A, i + rstart, &len, &rj, NULL));
418     for (j = 0; j < len; j++) {
419       if (rj[j] == i + rstart) {
420         len--;
421         break;
422       } /* don't count diagonal */
423     }
424     nzeros += len;
425     PetscCall(MatRestoreRow(A, i + rstart, &len, &rj, NULL));
426   }
427 
428   /* malloc space for nonzeros */
429   PetscCall(PetscMalloc1(nzeros + 1, &a));
430   PetscCall(PetscMalloc1(N + 1, &ia));
431   PetscCall(PetscMalloc1(nzeros + 1, &ja));
432 
433   nzeros = 0;
434   ia[0]  = 0;
435   for (i = 0; i < m; i++) {
436     PetscCall(MatGetRow(A, i + rstart, &len, &rj, &ra));
437     cnt = 0;
438     for (j = 0; j < len; j++) {
439       if (rj[j] != i + rstart) { /* if not diagonal */
440         a[nzeros + cnt]    = (PetscInt)PetscAbsScalar(ra[j]);
441         ja[nzeros + cnt++] = rj[j];
442       }
443     }
444     PetscCall(MatRestoreRow(A, i + rstart, &len, &rj, &ra));
445     nzeros += cnt;
446     ia[i + 1] = nzeros;
447   }
448 
449   PetscCall(PetscObjectGetComm((PetscObject)A, &comm));
450   PetscCall(MatCreate(comm, &B));
451   PetscCall(MatSetSizes(B, m, PETSC_DETERMINE, PETSC_DETERMINE, N));
452   PetscCall(MatSetType(B, type));
453   PetscCall(MatMPIAdjSetPreallocation(B, ia, ja, a));
454 
455   if (reuse == MAT_INPLACE_MATRIX) {
456     PetscCall(MatHeaderReplace(A, &B));
457   } else {
458     *newmat = B;
459   }
460   PetscFunctionReturn(PETSC_SUCCESS);
461 }
462 
463 static PetscErrorCode MatSetValues_MPIAdj(Mat A, PetscInt m, const PetscInt *rows, PetscInt n, const PetscInt *cols, const PetscScalar *values, InsertMode im)
464 {
465   Mat_MPIAdj *adj = (Mat_MPIAdj *)A->data;
466   PetscInt    rStart, rEnd, cStart, cEnd;
467 
468   PetscFunctionBegin;
469   PetscCheck(!adj->i, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Matrix is already assembled, cannot change its values");
470   PetscCall(MatGetOwnershipRange(A, &rStart, &rEnd));
471   PetscCall(MatGetOwnershipRangeColumn(A, &cStart, &cEnd));
472   if (!adj->ht) {
473     PetscCall(PetscHSetIJCreate(&adj->ht));
474     PetscCall(MatStashCreate_Private(PetscObjectComm((PetscObject)A), 1, &A->stash));
475     PetscCall(PetscLayoutSetUp(A->rmap));
476     PetscCall(PetscLayoutSetUp(A->cmap));
477   }
478   for (PetscInt r = 0; r < m; ++r) {
479     PetscHashIJKey key;
480 
481     key.i = rows[r];
482     if (key.i < 0) continue;
483     if ((key.i < rStart) || (key.i >= rEnd)) {
484       PetscCall(MatStashValuesRow_Private(&A->stash, key.i, n, cols, values, PETSC_FALSE));
485     } else {
486       for (PetscInt c = 0; c < n; ++c) {
487         key.j = cols[c];
488         if (key.j < 0 || key.i == key.j) continue;
489         PetscCall(PetscHSetIJAdd(adj->ht, key));
490       }
491     }
492   }
493   PetscFunctionReturn(PETSC_SUCCESS);
494 }
495 
496 static PetscErrorCode MatAssemblyBegin_MPIAdj(Mat A, MatAssemblyType type)
497 {
498   PetscInt    nstash, reallocs;
499   Mat_MPIAdj *adj = (Mat_MPIAdj *)A->data;
500 
501   PetscFunctionBegin;
502   if (!adj->ht) {
503     PetscCall(PetscHSetIJCreate(&adj->ht));
504     PetscCall(PetscLayoutSetUp(A->rmap));
505     PetscCall(PetscLayoutSetUp(A->cmap));
506   }
507   PetscCall(MatStashScatterBegin_Private(A, &A->stash, A->rmap->range));
508   PetscCall(MatStashGetInfo_Private(&A->stash, &nstash, &reallocs));
509   PetscCall(PetscInfo(A, "Stash has %" PetscInt_FMT " entries, uses %" PetscInt_FMT " mallocs.\n", nstash, reallocs));
510   PetscFunctionReturn(PETSC_SUCCESS);
511 }
512 
513 static PetscErrorCode MatAssemblyEnd_MPIAdj(Mat A, MatAssemblyType type)
514 {
515   PetscScalar   *val;
516   PetscInt      *row, *col, m, rstart, *rowstarts;
517   PetscInt       i, j, ncols, flg, nz;
518   PetscMPIInt    n;
519   Mat_MPIAdj    *adj = (Mat_MPIAdj *)A->data;
520   PetscHashIter  hi;
521   PetscHashIJKey key;
522   PetscHSetIJ    ht = adj->ht;
523 
524   PetscFunctionBegin;
525   while (1) {
526     PetscCall(MatStashScatterGetMesg_Private(&A->stash, &n, &row, &col, &val, &flg));
527     if (!flg) break;
528 
529     for (i = 0; i < n;) {
530       /* Identify the consecutive vals belonging to the same row */
531       for (j = i, rstart = row[j]; j < n; j++) {
532         if (row[j] != rstart) break;
533       }
534       if (j < n) ncols = j - i;
535       else ncols = n - i;
536       /* Set all these values with a single function call */
537       PetscCall(MatSetValues_MPIAdj(A, 1, row + i, ncols, col + i, val + i, INSERT_VALUES));
538       i = j;
539     }
540   }
541   PetscCall(MatStashScatterEnd_Private(&A->stash));
542   PetscCall(MatStashDestroy_Private(&A->stash));
543 
544   PetscCall(MatGetLocalSize(A, &m, NULL));
545   PetscCall(MatGetOwnershipRange(A, &rstart, NULL));
546   PetscCall(PetscCalloc1(m + 1, &rowstarts));
547   PetscHashIterBegin(ht, hi);
548   for (; !PetscHashIterAtEnd(ht, hi);) {
549     PetscHashIterGetKey(ht, hi, key);
550     rowstarts[key.i - rstart + 1]++;
551     PetscHashIterNext(ht, hi);
552   }
553   for (i = 1; i < m + 1; i++) rowstarts[i] = rowstarts[i - 1] + rowstarts[i];
554 
555   PetscCall(PetscHSetIJGetSize(ht, &nz));
556   PetscCall(PetscMalloc1(nz, &col));
557   PetscHashIterBegin(ht, hi);
558   for (; !PetscHashIterAtEnd(ht, hi);) {
559     PetscHashIterGetKey(ht, hi, key);
560     col[rowstarts[key.i - rstart]++] = key.j;
561     PetscHashIterNext(ht, hi);
562   }
563   PetscCall(PetscHSetIJDestroy(&ht));
564   for (i = m; i > 0; i--) rowstarts[i] = rowstarts[i - 1];
565   rowstarts[0] = 0;
566 
567   for (PetscInt i = 0; i < m; i++) PetscCall(PetscSortInt(rowstarts[i + 1] - rowstarts[i], &col[rowstarts[i]]));
568 
569   adj->i       = rowstarts;
570   adj->j       = col;
571   adj->nz      = rowstarts[m];
572   adj->freeaij = PETSC_TRUE;
573   PetscFunctionReturn(PETSC_SUCCESS);
574 }
575 
576 static struct _MatOps MatOps_Values = {MatSetValues_MPIAdj,
577                                        MatGetRow_MPIAdj,
578                                        MatRestoreRow_MPIAdj,
579                                        NULL,
580                                        /* 4*/ NULL,
581                                        NULL,
582                                        NULL,
583                                        NULL,
584                                        NULL,
585                                        NULL,
586                                        /*10*/ NULL,
587                                        NULL,
588                                        NULL,
589                                        NULL,
590                                        NULL,
591                                        /*15*/ NULL,
592                                        MatEqual_MPIAdj,
593                                        NULL,
594                                        NULL,
595                                        NULL,
596                                        /*20*/ MatAssemblyBegin_MPIAdj,
597                                        MatAssemblyEnd_MPIAdj,
598                                        MatSetOption_MPIAdj,
599                                        NULL,
600                                        /*24*/ NULL,
601                                        NULL,
602                                        NULL,
603                                        NULL,
604                                        NULL,
605                                        /*29*/ NULL,
606                                        NULL,
607                                        NULL,
608                                        NULL,
609                                        NULL,
610                                        /*34*/ NULL,
611                                        NULL,
612                                        NULL,
613                                        NULL,
614                                        NULL,
615                                        /*39*/ NULL,
616                                        MatCreateSubMatrices_MPIAdj,
617                                        NULL,
618                                        NULL,
619                                        NULL,
620                                        /*44*/ NULL,
621                                        NULL,
622                                        MatShift_Basic,
623                                        NULL,
624                                        NULL,
625                                        /*49*/ NULL,
626                                        MatGetRowIJ_MPIAdj,
627                                        MatRestoreRowIJ_MPIAdj,
628                                        NULL,
629                                        NULL,
630                                        /*54*/ NULL,
631                                        NULL,
632                                        NULL,
633                                        NULL,
634                                        NULL,
635                                        /*59*/ NULL,
636                                        MatDestroy_MPIAdj,
637                                        MatView_MPIAdj,
638                                        MatConvertFrom_MPIAdj,
639                                        NULL,
640                                        /*64*/ NULL,
641                                        NULL,
642                                        NULL,
643                                        NULL,
644                                        NULL,
645                                        /*69*/ NULL,
646                                        NULL,
647                                        NULL,
648                                        NULL,
649                                        NULL,
650                                        /*74*/ NULL,
651                                        NULL,
652                                        NULL,
653                                        NULL,
654                                        NULL,
655                                        /*79*/ NULL,
656                                        NULL,
657                                        NULL,
658                                        NULL,
659                                        NULL,
660                                        /*84*/ NULL,
661                                        NULL,
662                                        NULL,
663                                        NULL,
664                                        NULL,
665                                        /*89*/ NULL,
666                                        NULL,
667                                        NULL,
668                                        NULL,
669                                        NULL,
670                                        /*94*/ NULL,
671                                        NULL,
672                                        NULL,
673                                        NULL,
674                                        NULL,
675                                        /*99*/ NULL,
676                                        NULL,
677                                        NULL,
678                                        NULL,
679                                        NULL,
680                                        /*104*/ NULL,
681                                        NULL,
682                                        NULL,
683                                        NULL,
684                                        NULL,
685                                        /*109*/ NULL,
686                                        NULL,
687                                        NULL,
688                                        NULL,
689                                        NULL,
690                                        /*114*/ NULL,
691                                        NULL,
692                                        NULL,
693                                        NULL,
694                                        NULL,
695                                        /*119*/ NULL,
696                                        NULL,
697                                        NULL,
698                                        NULL,
699                                        NULL,
700                                        /*124*/ NULL,
701                                        NULL,
702                                        NULL,
703                                        NULL,
704                                        MatCreateSubMatricesMPI_MPIAdj,
705                                        /*129*/ NULL,
706                                        NULL,
707                                        NULL,
708                                        NULL,
709                                        NULL,
710                                        /*134*/ NULL,
711                                        NULL,
712                                        NULL,
713                                        NULL,
714                                        NULL,
715                                        /*139*/ NULL,
716                                        NULL,
717                                        NULL,
718                                        NULL,
719                                        NULL,
720                                        /*144*/ NULL,
721                                        NULL,
722                                        NULL,
723                                        NULL,
724                                        NULL,
725                                        NULL,
726                                        /*150*/ NULL,
727                                        NULL};
728 
729 static PetscErrorCode MatMPIAdjSetPreallocation_MPIAdj(Mat B, PetscInt *i, PetscInt *j, PetscInt *values)
730 {
731   Mat_MPIAdj *b = (Mat_MPIAdj *)B->data;
732   PetscBool   useedgeweights;
733 
734   PetscFunctionBegin;
735   PetscCall(PetscLayoutSetUp(B->rmap));
736   PetscCall(PetscLayoutSetUp(B->cmap));
737   if (values) useedgeweights = PETSC_TRUE;
738   else useedgeweights = PETSC_FALSE;
739   /* Make everybody knows if they are using edge weights or not */
740   PetscCall(MPIU_Allreduce((int *)&useedgeweights, (int *)&b->useedgeweights, 1, MPI_INT, MPI_MAX, PetscObjectComm((PetscObject)B)));
741 
742   if (PetscDefined(USE_DEBUG)) {
743     PetscInt ii;
744 
745     PetscCheck(i[0] == 0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "First i[] index must be zero, instead it is %" PetscInt_FMT, i[0]);
746     for (ii = 1; ii < B->rmap->n; ii++) {
747       PetscCheck(i[ii] >= 0 && i[ii] >= i[ii - 1], PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "i[%" PetscInt_FMT "]=%" PetscInt_FMT " index is out of range: i[%" PetscInt_FMT "]=%" PetscInt_FMT, ii, i[ii], ii - 1, i[ii - 1]);
748     }
749     for (ii = 0; ii < i[B->rmap->n]; ii++) PetscCheck(j[ii] >= 0 && j[ii] < B->cmap->N, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Column index %" PetscInt_FMT " out of range %" PetscInt_FMT, ii, j[ii]);
750   }
751   b->j      = j;
752   b->i      = i;
753   b->values = values;
754 
755   b->nz        = i[B->rmap->n];
756   b->diag      = NULL;
757   b->symmetric = PETSC_FALSE;
758   b->freeaij   = PETSC_TRUE;
759 
760   B->ops->assemblybegin = NULL;
761   B->ops->assemblyend   = NULL;
762   PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY));
763   PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY));
764   PetscCall(MatStashDestroy_Private(&B->stash));
765   PetscFunctionReturn(PETSC_SUCCESS);
766 }
767 
768 static PetscErrorCode MatMPIAdjCreateNonemptySubcommMat_MPIAdj(Mat A, Mat *B)
769 {
770   Mat_MPIAdj     *a = (Mat_MPIAdj *)A->data;
771   const PetscInt *ranges;
772   MPI_Comm        acomm, bcomm;
773   MPI_Group       agroup, bgroup;
774   PetscMPIInt     i, rank, size, nranks, *ranks;
775 
776   PetscFunctionBegin;
777   *B = NULL;
778   PetscCall(PetscObjectGetComm((PetscObject)A, &acomm));
779   PetscCallMPI(MPI_Comm_size(acomm, &size));
780   PetscCallMPI(MPI_Comm_size(acomm, &rank));
781   PetscCall(MatGetOwnershipRanges(A, &ranges));
782   for (i = 0, nranks = 0; i < size; i++) {
783     if (ranges[i + 1] - ranges[i] > 0) nranks++;
784   }
785   if (nranks == size) { /* All ranks have a positive number of rows, so we do not need to create a subcomm; */
786     PetscCall(PetscObjectReference((PetscObject)A));
787     *B = A;
788     PetscFunctionReturn(PETSC_SUCCESS);
789   }
790 
791   PetscCall(PetscMalloc1(nranks, &ranks));
792   for (i = 0, nranks = 0; i < size; i++) {
793     if (ranges[i + 1] - ranges[i] > 0) ranks[nranks++] = i;
794   }
795   PetscCallMPI(MPI_Comm_group(acomm, &agroup));
796   PetscCallMPI(MPI_Group_incl(agroup, nranks, ranks, &bgroup));
797   PetscCall(PetscFree(ranks));
798   PetscCallMPI(MPI_Comm_create(acomm, bgroup, &bcomm));
799   PetscCallMPI(MPI_Group_free(&agroup));
800   PetscCallMPI(MPI_Group_free(&bgroup));
801   if (bcomm != MPI_COMM_NULL) {
802     PetscInt    m, N;
803     Mat_MPIAdj *b;
804     PetscCall(MatGetLocalSize(A, &m, NULL));
805     PetscCall(MatGetSize(A, NULL, &N));
806     PetscCall(MatCreateMPIAdj(bcomm, m, N, a->i, a->j, a->values, B));
807     b          = (Mat_MPIAdj *)(*B)->data;
808     b->freeaij = PETSC_FALSE;
809     PetscCallMPI(MPI_Comm_free(&bcomm));
810   }
811   PetscFunctionReturn(PETSC_SUCCESS);
812 }
813 
814 static PetscErrorCode MatMPIAdjToSeq_MPIAdj(Mat A, Mat *B)
815 {
816   PetscInt    M, N, *II, *J, NZ, nz, m, nzstart, i;
817   PetscInt   *Values = NULL;
818   Mat_MPIAdj *adj    = (Mat_MPIAdj *)A->data;
819   PetscMPIInt mnz, mm, *allnz, *allm, size, *dispnz, *dispm;
820 
821   PetscFunctionBegin;
822   PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)A), &size));
823   PetscCall(MatGetSize(A, &M, &N));
824   PetscCall(MatGetLocalSize(A, &m, NULL));
825   nz = adj->nz;
826   PetscCheck(adj->i[m] == nz, PETSC_COMM_SELF, PETSC_ERR_PLIB, "nz %" PetscInt_FMT " not correct i[m] %" PetscInt_FMT, nz, adj->i[m]);
827   PetscCall(MPIU_Allreduce(&nz, &NZ, 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject)A)));
828 
829   PetscCall(PetscMPIIntCast(nz, &mnz));
830   PetscCall(PetscMalloc2(size, &allnz, size, &dispnz));
831   PetscCallMPI(MPI_Allgather(&mnz, 1, MPI_INT, allnz, 1, MPI_INT, PetscObjectComm((PetscObject)A)));
832   dispnz[0] = 0;
833   for (i = 1; i < size; i++) dispnz[i] = dispnz[i - 1] + allnz[i - 1];
834   if (adj->values) {
835     PetscCall(PetscMalloc1(NZ, &Values));
836     PetscCallMPI(MPI_Allgatherv(adj->values, mnz, MPIU_INT, Values, allnz, dispnz, MPIU_INT, PetscObjectComm((PetscObject)A)));
837   }
838   PetscCall(PetscMalloc1(NZ, &J));
839   PetscCallMPI(MPI_Allgatherv(adj->j, mnz, MPIU_INT, J, allnz, dispnz, MPIU_INT, PetscObjectComm((PetscObject)A)));
840   PetscCall(PetscFree2(allnz, dispnz));
841   PetscCallMPI(MPI_Scan(&nz, &nzstart, 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject)A)));
842   nzstart -= nz;
843   /* shift the i[] values so they will be correct after being received */
844   for (i = 0; i < m; i++) adj->i[i] += nzstart;
845   PetscCall(PetscMalloc1(M + 1, &II));
846   PetscCall(PetscMPIIntCast(m, &mm));
847   PetscCall(PetscMalloc2(size, &allm, size, &dispm));
848   PetscCallMPI(MPI_Allgather(&mm, 1, MPI_INT, allm, 1, MPI_INT, PetscObjectComm((PetscObject)A)));
849   dispm[0] = 0;
850   for (i = 1; i < size; i++) dispm[i] = dispm[i - 1] + allm[i - 1];
851   PetscCallMPI(MPI_Allgatherv(adj->i, mm, MPIU_INT, II, allm, dispm, MPIU_INT, PetscObjectComm((PetscObject)A)));
852   PetscCall(PetscFree2(allm, dispm));
853   II[M] = NZ;
854   /* shift the i[] values back */
855   for (i = 0; i < m; i++) adj->i[i] -= nzstart;
856   PetscCall(MatCreateMPIAdj(PETSC_COMM_SELF, M, N, II, J, Values, B));
857   PetscFunctionReturn(PETSC_SUCCESS);
858 }
859 
860 static PetscErrorCode MatMPIAdjToSeqRankZero_MPIAdj(Mat A, Mat *B)
861 {
862   PetscInt    M, N, *II, *J, NZ, nz, m, nzstart, i;
863   PetscInt   *Values = NULL;
864   Mat_MPIAdj *adj    = (Mat_MPIAdj *)A->data;
865   PetscMPIInt mnz, mm, *allnz = NULL, *allm, size, *dispnz, *dispm, rank;
866 
867   PetscFunctionBegin;
868   PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)A), &size));
869   PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)A), &rank));
870   PetscCall(MatGetSize(A, &M, &N));
871   PetscCall(MatGetLocalSize(A, &m, NULL));
872   nz = adj->nz;
873   PetscCheck(adj->i[m] == nz, PETSC_COMM_SELF, PETSC_ERR_PLIB, "nz %" PetscInt_FMT " not correct i[m] %" PetscInt_FMT, nz, adj->i[m]);
874   PetscCall(MPIU_Allreduce(&nz, &NZ, 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject)A)));
875 
876   PetscCall(PetscMPIIntCast(nz, &mnz));
877   if (!rank) PetscCall(PetscMalloc2(size, &allnz, size, &dispnz));
878   PetscCallMPI(MPI_Gather(&mnz, 1, MPI_INT, allnz, 1, MPI_INT, 0, PetscObjectComm((PetscObject)A)));
879   if (!rank) {
880     dispnz[0] = 0;
881     for (i = 1; i < size; i++) dispnz[i] = dispnz[i - 1] + allnz[i - 1];
882     if (adj->values) {
883       PetscCall(PetscMalloc1(NZ, &Values));
884       PetscCallMPI(MPI_Gatherv(adj->values, mnz, MPIU_INT, Values, allnz, dispnz, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
885     }
886     PetscCall(PetscMalloc1(NZ, &J));
887     PetscCallMPI(MPI_Gatherv(adj->j, mnz, MPIU_INT, J, allnz, dispnz, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
888     PetscCall(PetscFree2(allnz, dispnz));
889   } else {
890     if (adj->values) PetscCallMPI(MPI_Gatherv(adj->values, mnz, MPIU_INT, NULL, NULL, NULL, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
891     PetscCallMPI(MPI_Gatherv(adj->j, mnz, MPIU_INT, NULL, NULL, NULL, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
892   }
893   PetscCallMPI(MPI_Scan(&nz, &nzstart, 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject)A)));
894   nzstart -= nz;
895   /* shift the i[] values so they will be correct after being received */
896   for (i = 0; i < m; i++) adj->i[i] += nzstart;
897   PetscCall(PetscMPIIntCast(m, &mm));
898   if (!rank) {
899     PetscCall(PetscMalloc1(M + 1, &II));
900     PetscCall(PetscMalloc2(size, &allm, size, &dispm));
901     PetscCallMPI(MPI_Gather(&mm, 1, MPI_INT, allm, 1, MPI_INT, 0, PetscObjectComm((PetscObject)A)));
902     dispm[0] = 0;
903     for (i = 1; i < size; i++) dispm[i] = dispm[i - 1] + allm[i - 1];
904     PetscCallMPI(MPI_Gatherv(adj->i, mm, MPIU_INT, II, allm, dispm, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
905     PetscCall(PetscFree2(allm, dispm));
906     II[M] = NZ;
907   } else {
908     PetscCallMPI(MPI_Gather(&mm, 1, MPI_INT, NULL, 1, MPI_INT, 0, PetscObjectComm((PetscObject)A)));
909     PetscCallMPI(MPI_Gatherv(adj->i, mm, MPIU_INT, NULL, NULL, NULL, MPIU_INT, 0, PetscObjectComm((PetscObject)A)));
910   }
911   /* shift the i[] values back */
912   for (i = 0; i < m; i++) adj->i[i] -= nzstart;
913   if (!rank) PetscCall(MatCreateMPIAdj(PETSC_COMM_SELF, M, N, II, J, Values, B));
914   PetscFunctionReturn(PETSC_SUCCESS);
915 }
916 
917 /*@
918   MatMPIAdjCreateNonemptySubcommMat - create the same `MATMPIADJ` matrix on a subcommunicator containing only processes owning a positive number of rows
919 
920   Collective
921 
922   Input Parameter:
923 . A - original `MATMPIADJ` matrix
924 
925   Output Parameter:
926 . B - matrix on subcommunicator, `NULL` on ranks that owned zero rows of `A`
927 
928   Level: developer
929 
930   Note:
931   This function is mostly useful for internal use by mesh partitioning packages that require that every process owns at least one row.
932 
933   The matrix `B` should be destroyed with `MatDestroy()`. The arrays are not copied, so `B` should be destroyed before `A` is destroyed.
934 
935 .seealso: [](ch_matrices), `Mat`, `MATMPIADJ`, `MatCreateMPIAdj()`
936 @*/
937 PetscErrorCode MatMPIAdjCreateNonemptySubcommMat(Mat A, Mat *B)
938 {
939   PetscFunctionBegin;
940   PetscValidHeaderSpecific(A, MAT_CLASSID, 1);
941   PetscUseMethod(A, "MatMPIAdjCreateNonemptySubcommMat_C", (Mat, Mat *), (A, B));
942   PetscFunctionReturn(PETSC_SUCCESS);
943 }
944 
945 /*MC
946    MATMPIADJ - MATMPIADJ = "mpiadj" - A matrix type to be used for distributed adjacency matrices,
947    intended for use constructing orderings and partitionings.
948 
949   Level: beginner
950 
951   Note:
952     You can provide values to the matrix using `MatMPIAdjSetPreallocation()`, `MatCreateMPIAdj()`, or
953     by calling `MatSetValues()` and `MatAssemblyBegin()` followed by `MatAssemblyEnd()`
954 
955 .seealso: [](ch_matrices), `Mat`, `MatCreateMPIAdj()`, `MatMPIAdjSetPreallocation()`, `MatSetValues()`
956 M*/
957 PETSC_EXTERN PetscErrorCode MatCreate_MPIAdj(Mat B)
958 {
959   Mat_MPIAdj *b;
960 
961   PetscFunctionBegin;
962   PetscCall(PetscNew(&b));
963   B->data         = (void *)b;
964   B->ops[0]       = MatOps_Values;
965   B->assembled    = PETSC_FALSE;
966   B->preallocated = PETSC_TRUE; /* so that MatSetValues() may be used */
967 
968   PetscCall(PetscObjectComposeFunction((PetscObject)B, "MatMPIAdjSetPreallocation_C", MatMPIAdjSetPreallocation_MPIAdj));
969   PetscCall(PetscObjectComposeFunction((PetscObject)B, "MatMPIAdjCreateNonemptySubcommMat_C", MatMPIAdjCreateNonemptySubcommMat_MPIAdj));
970   PetscCall(PetscObjectComposeFunction((PetscObject)B, "MatMPIAdjToSeq_C", MatMPIAdjToSeq_MPIAdj));
971   PetscCall(PetscObjectComposeFunction((PetscObject)B, "MatMPIAdjToSeqRankZero_C", MatMPIAdjToSeqRankZero_MPIAdj));
972   PetscCall(PetscObjectChangeTypeName((PetscObject)B, MATMPIADJ));
973   PetscFunctionReturn(PETSC_SUCCESS);
974 }
975 
976 /*@C
977   MatMPIAdjToSeq - Converts an parallel `MATMPIADJ` matrix to complete `MATMPIADJ` on each process (needed by sequential partitioner)
978 
979   Logically Collective
980 
981   Input Parameter:
982 . A - the matrix
983 
984   Output Parameter:
985 . B - the same matrix on all processes
986 
987   Level: intermediate
988 
989 .seealso: [](ch_matrices), `Mat`, `MATMPIADJ`, `MatCreate()`, `MatCreateMPIAdj()`, `MatSetValues()`, `MatMPIAdjToSeqRankZero()`
990 @*/
991 PetscErrorCode MatMPIAdjToSeq(Mat A, Mat *B)
992 {
993   PetscFunctionBegin;
994   PetscUseMethod(A, "MatMPIAdjToSeq_C", (Mat, Mat *), (A, B));
995   PetscFunctionReturn(PETSC_SUCCESS);
996 }
997 
998 /*@C
999   MatMPIAdjToSeqRankZero - Converts an parallel `MATMPIADJ` matrix to complete `MATMPIADJ` on rank zero (needed by sequential partitioner)
1000 
1001   Logically Collective
1002 
1003   Input Parameter:
1004 . A - the matrix
1005 
1006   Output Parameter:
1007 . B - the same matrix on rank zero, not set on other ranks
1008 
1009   Level: intermediate
1010 
1011   Note:
1012   This routine has the advantage on systems with multiple ranks per node since only one copy of the matrix
1013   is stored on the first node, instead of the number of ranks copies. This can allow partitioning much larger
1014   parallel graph sequentially.
1015 
1016 .seealso: [](ch_matrices), `Mat`, `MATMPIADJ`, `MatCreate()`, `MatCreateMPIAdj()`, `MatSetValues()`, `MatMPIAdjToSeq()`
1017 @*/
1018 PetscErrorCode MatMPIAdjToSeqRankZero(Mat A, Mat *B)
1019 {
1020   PetscFunctionBegin;
1021   PetscUseMethod(A, "MatMPIAdjToSeqRankZero_C", (Mat, Mat *), (A, B));
1022   PetscFunctionReturn(PETSC_SUCCESS);
1023 }
1024 
1025 /*@C
1026   MatMPIAdjSetPreallocation - Sets the array used for storing the matrix elements
1027 
1028   Logically Collective
1029 
1030   Input Parameters:
1031 + B      - the matrix
1032 . i      - the indices into `j` for the start of each row
1033 . j      - the column indices for each row (sorted for each row).
1034        The indices in `i` and `j` start with zero (NOT with one).
1035 - values - [use `NULL` if not provided] edge weights
1036 
1037   Level: intermediate
1038 
1039 .seealso: [](ch_matrices), `Mat`, `MatCreate()`, `MatCreateMPIAdj()`, `MatSetValues()`, `MATMPIADJ`
1040 @*/
1041 PetscErrorCode MatMPIAdjSetPreallocation(Mat B, PetscInt *i, PetscInt *j, PetscInt *values)
1042 {
1043   PetscFunctionBegin;
1044   PetscTryMethod(B, "MatMPIAdjSetPreallocation_C", (Mat, PetscInt *, PetscInt *, PetscInt *), (B, i, j, values));
1045   PetscFunctionReturn(PETSC_SUCCESS);
1046 }
1047 
1048 /*@C
1049   MatCreateMPIAdj - Creates a sparse matrix representing an adjacency list.
1050   The matrix does not have numerical values associated with it, but is
1051   intended for ordering (to reduce bandwidth etc) and partitioning.
1052 
1053   Collective
1054 
1055   Input Parameters:
1056 + comm   - MPI communicator
1057 . m      - number of local rows
1058 . N      - number of global columns
1059 . i      - the indices into `j` for the start of each row
1060 . j      - the column indices for each row (sorted for each row).
1061 - values - the values
1062 
1063   Output Parameter:
1064 . A - the matrix
1065 
1066   Level: intermediate
1067 
1068   Notes:
1069   The indices in `i` and `j` start with zero (NOT with one).
1070 
1071   You must NOT free the `i`, `values` and `j` arrays yourself. PETSc will free them
1072   when the matrix is destroyed; you must allocate them with `PetscMalloc()`. If you
1073   call from Fortran you need not create the arrays with `PetscMalloc()`.
1074 
1075   You should not include the matrix diagonals.
1076 
1077   If you already have a matrix, you can create its adjacency matrix by a call
1078   to `MatConvert()`, specifying a type of `MATMPIADJ`.
1079 
1080   Possible values for `MatSetOption()` - `MAT_STRUCTURALLY_SYMMETRIC`
1081 
1082 .seealso: [](ch_matrices), `Mat`, `MatCreate()`, `MatConvert()`, `MatGetOrdering()`, `MATMPIADJ`, `MatMPIAdjSetPreallocation()`
1083 @*/
1084 PetscErrorCode MatCreateMPIAdj(MPI_Comm comm, PetscInt m, PetscInt N, PetscInt *i, PetscInt *j, PetscInt *values, Mat *A)
1085 {
1086   PetscFunctionBegin;
1087   PetscCall(MatCreate(comm, A));
1088   PetscCall(MatSetSizes(*A, m, PETSC_DETERMINE, PETSC_DETERMINE, N));
1089   PetscCall(MatSetType(*A, MATMPIADJ));
1090   PetscCall(MatMPIAdjSetPreallocation(*A, i, j, values));
1091   PetscFunctionReturn(PETSC_SUCCESS);
1092 }
1093