xref: /petsc/src/ksp/pc/impls/bddc/bddcschurs.c (revision 41c3ba1b6f99efbbbf5c2c55e2829b66747659d9)
1 #include <../src/ksp/pc/impls/bddc/bddc.h>
2 #include <../src/ksp/pc/impls/bddc/bddcprivate.h>
3 
4 static PetscErrorCode PCBDDCAdjGetNextLayer_Private(PetscInt*,PetscInt,PetscBT,PetscInt*,PetscInt*,PetscInt*);
5 
6 #undef __FUNCT__
7 #define __FUNCT__ "PCBDDCSubSchursSetUpNew"
8 PetscErrorCode PCBDDCSubSchursSetUpNew(PCBDDCSubSchurs sub_schurs, PetscInt xadj[], PetscInt adjncy[], PetscInt nlayers)
9 {
10   Mat                    A_II,A_IB,A_BI,A_BB;
11   Mat                    AE_II,*AE_IE,*AE_EI,*AE_EE;
12   IS                     is_I,*is_subset_B;
13   ISLocalToGlobalMapping BtoNmap;
14   PetscInt               i;
15   PetscBool              implicit_schurs;
16   PetscErrorCode         ierr;
17 
18   PetscFunctionBegin;
19   ierr = PetscObjectTypeCompare((PetscObject)sub_schurs->S,MATSCHURCOMPLEMENT,&implicit_schurs);CHKERRQ(ierr);
20 
21   /* allocate space for schur complements */
22   ierr = PetscMalloc5(sub_schurs->n_subs,&sub_schurs->is_AEj_I,
23                       sub_schurs->n_subs,&sub_schurs->is_AEj_B,
24                       sub_schurs->n_subs,&sub_schurs->S_Ej,
25                       sub_schurs->n_subs,&sub_schurs->work1,
26                       sub_schurs->n_subs,&sub_schurs->work2);CHKERRQ(ierr);
27 
28   /* get Schur complement matrices */
29   if (implicit_schurs) {
30     ierr = MatSchurComplementGetSubMatrices(sub_schurs->S,&A_II,NULL,&A_IB,&A_BI,&A_BB);CHKERRQ(ierr);
31     ierr = PetscMalloc4(sub_schurs->n_subs,&is_subset_B,
32                         sub_schurs->n_subs,&AE_IE,
33                         sub_schurs->n_subs,&AE_EI,
34                         sub_schurs->n_subs,&AE_EE);CHKERRQ(ierr);
35   }
36 
37   /* determine interior problems */
38   if (nlayers >= 0 && xadj != NULL && adjncy != NULL) { /* Interior problems can be different from the original one */
39     PetscBT                touched;
40     const PetscInt*        idx_B;
41     PetscInt               n_I,n_B,n_local_dofs,n_prev_added,j,layer,*local_numbering;
42 
43     /* get sizes */
44     ierr = ISGetLocalSize(sub_schurs->is_I,&n_I);CHKERRQ(ierr);
45     ierr = ISGetLocalSize(sub_schurs->is_B,&n_B);CHKERRQ(ierr);
46 
47     ierr = PetscMalloc1(n_I+n_B,&local_numbering);CHKERRQ(ierr);
48     ierr = PetscBTCreate(n_I+n_B,&touched);CHKERRQ(ierr);
49     ierr = PetscBTMemzero(n_I+n_B,touched);CHKERRQ(ierr);
50 
51     /* all boundary dofs must be skipped when adding layers */
52     ierr = ISGetIndices(sub_schurs->is_B,&idx_B);CHKERRQ(ierr);
53     for (j=0;j<n_B;j++) {
54       ierr = PetscBTSet(touched,idx_B[j]);CHKERRQ(ierr);
55     }
56     ierr = PetscMemcpy(local_numbering,idx_B,n_B*sizeof(PetscInt));CHKERRQ(ierr);
57     ierr = ISRestoreIndices(sub_schurs->is_B,&idx_B);CHKERRQ(ierr);
58 
59     /* add prescribed number of layers of dofs */
60     n_local_dofs = n_B;
61     n_prev_added = n_B;
62     for (layer=0;layer<nlayers;layer++) {
63       PetscInt n_added;
64       if (n_local_dofs == n_I+n_B) break;
65       if (n_local_dofs > n_I+n_B) {
66         SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Error querying layer %d. Out of bound access (%d > %d)",layer,n_local_dofs,n_I+n_B);
67       }
68       ierr = PCBDDCAdjGetNextLayer_Private(local_numbering+n_local_dofs,n_prev_added,touched,xadj,adjncy,&n_added);CHKERRQ(ierr);
69       n_prev_added = n_added;
70       n_local_dofs += n_added;
71       if (!n_added) break;
72     }
73     ierr = PetscBTDestroy(&touched);CHKERRQ(ierr);
74 
75     /* IS for I dofs in original numbering */
76     ierr = ISCreateGeneral(PetscObjectComm((PetscObject)sub_schurs->is_I),n_local_dofs-n_B,local_numbering+n_B,PETSC_COPY_VALUES,&sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
77     ierr = PetscFree(local_numbering);CHKERRQ(ierr);
78     ierr = ISSort(sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
79     /* IS for I dofs in boundary numbering */
80     if (implicit_schurs) {
81       ISLocalToGlobalMapping ItoNmap;
82       ierr = ISLocalToGlobalMappingCreateIS(sub_schurs->is_I,&ItoNmap);CHKERRQ(ierr);
83       ierr = ISGlobalToLocalMappingApplyIS(ItoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_I[0],&is_I);CHKERRQ(ierr);
84       ierr = ISLocalToGlobalMappingDestroy(&ItoNmap);CHKERRQ(ierr);
85 
86       /* II block */
87       ierr = MatGetSubMatrix(A_II,is_I,is_I,MAT_INITIAL_MATRIX,&AE_II);CHKERRQ(ierr);
88     }
89   } else {
90     PetscInt n_I;
91 
92     /* IS for I dofs in original numbering */
93     ierr = PetscObjectReference((PetscObject)sub_schurs->is_I);CHKERRQ(ierr);
94     sub_schurs->is_AEj_I[0] = sub_schurs->is_I;
95 
96     /* IS for I dofs in I numbering (strided 1) */
97     if (implicit_schurs) {
98       ierr = ISGetSize(sub_schurs->is_I,&n_I);CHKERRQ(ierr);
99       ierr = ISCreateStride(PetscObjectComm((PetscObject)sub_schurs->is_I),n_I,0,1,&is_I);CHKERRQ(ierr);
100 
101       /* II block is the same */
102       ierr = PetscObjectReference((PetscObject)A_II);CHKERRQ(ierr);
103       AE_II = A_II;
104     }
105   }
106 
107   /* TODO: just for compatibility with the previous version, needs to be fixed */
108   for (i=1;i<sub_schurs->n_subs;i++) {
109     ierr = PetscObjectReference((PetscObject)sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
110     sub_schurs->is_AEj_I[i] = sub_schurs->is_AEj_I[0];
111   }
112 
113   if (implicit_schurs) {
114     /* subsets in original and boundary numbering */
115     ierr = ISLocalToGlobalMappingCreateIS(sub_schurs->is_B,&BtoNmap);CHKERRQ(ierr);
116     for (i=0;i<sub_schurs->n_subs;i++) {
117       ierr = ISDuplicate(sub_schurs->is_subs[i],&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
118       ierr = ISSort(sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
119       ierr = ISGlobalToLocalMappingApplyIS(BtoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_B[i],&is_subset_B[i]);CHKERRQ(ierr);
120     }
121     ierr = ISLocalToGlobalMappingDestroy(&BtoNmap);CHKERRQ(ierr);
122 
123     /* EE block */
124     for (i=0;i<sub_schurs->n_subs;i++) {
125       ierr = MatGetSubMatrix(A_BB,is_subset_B[i],is_subset_B[i],MAT_INITIAL_MATRIX,&AE_EE[i]);CHKERRQ(ierr);
126     }
127     /* IE block */
128     for (i=0;i<sub_schurs->n_subs;i++) {
129       ierr = MatGetSubMatrix(A_IB,is_I,is_subset_B[i],MAT_INITIAL_MATRIX,&AE_IE[i]);CHKERRQ(ierr);
130     }
131     /* EI block */
132     for (i=0;i<sub_schurs->n_subs;i++) {
133       ierr = MatGetSubMatrix(A_BI,is_subset_B[i],is_I,MAT_INITIAL_MATRIX,&AE_EI[i]);CHKERRQ(ierr);
134     }
135 
136     /* setup Schur complements on subset */
137     for (i=0;i<sub_schurs->n_subs;i++) {
138       ierr = MatCreateSchurComplement(AE_II,AE_II,AE_IE[i],AE_EI[i],AE_EE[i],&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
139       ierr = MatCreateVecs(sub_schurs->S_Ej[i],&sub_schurs->work1[i],&sub_schurs->work2[i]);CHKERRQ(ierr);
140       if (AE_II == A_II) { /* we can reuse the same ksp */
141         KSP ksp;
142         ierr = MatSchurComplementGetKSP(sub_schurs->S,&ksp);CHKERRQ(ierr);
143         ierr = MatSchurComplementSetKSP(sub_schurs->S_Ej[i],ksp);CHKERRQ(ierr);
144       } else { /* build new ksp object which inherits ksp and pc types from the original one */
145         KSP      origksp,schurksp;
146         PC       origpc,schurpc;
147         KSPType  ksp_type;
148         PCType   pc_type;
149         PetscInt n_internal;
150 
151         ierr = MatSchurComplementGetKSP(sub_schurs->S,&origksp);CHKERRQ(ierr);
152         ierr = MatSchurComplementGetKSP(sub_schurs->S_Ej[i],&schurksp);CHKERRQ(ierr);
153         ierr = KSPGetType(origksp,&ksp_type);CHKERRQ(ierr);
154         ierr = KSPSetType(schurksp,ksp_type);CHKERRQ(ierr);
155         ierr = KSPGetPC(schurksp,&schurpc);CHKERRQ(ierr);
156         ierr = KSPGetPC(origksp,&origpc);CHKERRQ(ierr);
157         ierr = PCGetType(origpc,&pc_type);CHKERRQ(ierr);
158         ierr = PCSetType(schurpc,pc_type);CHKERRQ(ierr);
159         ierr = ISGetSize(is_I,&n_internal);CHKERRQ(ierr);
160         if (n_internal) { /* UMFPACK gives error with 0 sized problems */
161           MatSolverPackage solver=NULL;
162           ierr = PCFactorGetMatSolverPackage(origpc,(const MatSolverPackage*)&solver);CHKERRQ(ierr);
163           if (solver) {
164             ierr = PCFactorSetMatSolverPackage(schurpc,solver);CHKERRQ(ierr);
165           }
166         }
167         ierr = KSPSetUp(schurksp);CHKERRQ(ierr);
168       }
169     }
170     /* free */
171     ierr = ISDestroy(&is_I);CHKERRQ(ierr);
172     ierr = MatDestroy(&AE_II);CHKERRQ(ierr);
173     for (i=0;i<sub_schurs->n_subs;i++) {
174       ierr = MatDestroy(&AE_EE[i]);CHKERRQ(ierr);
175       ierr = MatDestroy(&AE_IE[i]);CHKERRQ(ierr);
176       ierr = MatDestroy(&AE_EI[i]);CHKERRQ(ierr);
177       ierr = ISDestroy(&is_subset_B[i]);CHKERRQ(ierr);
178     }
179     ierr = PetscFree4(is_subset_B,AE_IE,AE_EI,AE_EE);CHKERRQ(ierr);
180   }
181   PetscFunctionReturn(0);
182 }
183 
184 #undef __FUNCT__
185 #define __FUNCT__ "PCBDDCSubSchursInit"
186 PetscErrorCode PCBDDCSubSchursInit(PCBDDCSubSchurs sub_schurs, Mat A, Mat S, IS is_I, IS is_B, PCBDDCGraph graph, PetscInt seqthreshold)
187 {
188   IS                  *faces,*edges,*all_cc;
189   PetscInt            *index_sequential,*index_parallel;
190   PetscInt            *auxlocal_sequential,*auxlocal_parallel;
191   PetscInt            *auxglobal_sequential,*auxglobal_parallel;
192   PetscInt            *auxmapping;//,*idxs;
193   PetscInt            i,max_subset_size;
194   PetscInt            n_sequential_problems,n_local_sequential_problems,n_parallel_problems,n_local_parallel_problems;
195   PetscInt            n_faces,n_edges,n_all_cc;
196   PetscBool           is_sorted;
197   PetscErrorCode  ierr;
198 
199   PetscFunctionBegin;
200   ierr = ISSorted(is_I,&is_sorted);CHKERRQ(ierr);
201   if (!is_sorted) {
202     SETERRQ(PetscObjectComm((PetscObject)is_I),PETSC_ERR_PLIB,"IS for I dofs should be shorted");
203   }
204   ierr = ISSorted(is_B,&is_sorted);CHKERRQ(ierr);
205   if (!is_sorted) {
206     SETERRQ(PetscObjectComm((PetscObject)is_B),PETSC_ERR_PLIB,"IS for B dofs should be shorted");
207   }
208 
209   /* reset any previous data */
210   ierr = PCBDDCSubSchursReset(sub_schurs);CHKERRQ(ierr);
211 
212   /* get index sets for faces and edges */
213   ierr = PCBDDCGraphGetCandidatesIS(graph,&n_faces,&faces,&n_edges,&edges,NULL);CHKERRQ(ierr);
214   n_all_cc = n_faces+n_edges;
215   ierr = PetscMalloc1(n_all_cc,&all_cc);CHKERRQ(ierr);
216   for (i=0;i<n_faces;i++) {
217     all_cc[i] = faces[i];
218   }
219   for (i=0;i<n_edges;i++) {
220     all_cc[n_faces+i] = edges[i];
221   }
222   ierr = PetscFree(faces);CHKERRQ(ierr);
223   ierr = PetscFree(edges);CHKERRQ(ierr);
224 
225   /* map interface's subsets */
226   max_subset_size = 0;
227   for (i=0;i<n_all_cc;i++) {
228     PetscInt subset_size;
229     ierr = ISGetLocalSize(all_cc[i],&subset_size);CHKERRQ(ierr);
230     max_subset_size = PetscMax(max_subset_size,subset_size);
231   }
232   ierr = PetscMalloc1(max_subset_size,&auxmapping);CHKERRQ(ierr);
233   ierr = PetscMalloc2(graph->ncc,&auxlocal_sequential,
234                       graph->ncc,&auxlocal_parallel);CHKERRQ(ierr);
235   ierr = PetscMalloc2(graph->ncc,&index_sequential,
236                       graph->ncc,&index_parallel);CHKERRQ(ierr);
237 
238   /* if threshold is negative, uses all sequential problems */
239   if (seqthreshold < 0) seqthreshold = max_subset_size;
240 
241   /* determine which problem has to be solved in parallel or sequentially */
242   n_local_sequential_problems = 0;
243   n_local_parallel_problems = 0;
244   for (i=0;i<n_all_cc;i++) {
245     PetscInt       subset_size,j,min_loc = 0;
246     const PetscInt *idxs;
247 
248     ierr = ISGetLocalSize(all_cc[i],&subset_size);CHKERRQ(ierr);
249     ierr = ISGetIndices(all_cc[i],&idxs);CHKERRQ(ierr);
250     ierr = ISLocalToGlobalMappingApply(graph->l2gmap,subset_size,idxs,auxmapping);CHKERRQ(ierr);
251     for (j=1;j<subset_size;j++) {
252       if (auxmapping[j]<auxmapping[min_loc]) {
253         min_loc = j;
254       }
255     }
256     if (subset_size > seqthreshold) {
257       index_parallel[n_local_parallel_problems] = i;
258       auxlocal_parallel[n_local_parallel_problems] = idxs[min_loc];
259       n_local_parallel_problems++;
260     } else {
261       index_sequential[n_local_sequential_problems] = i;
262       auxlocal_sequential[n_local_sequential_problems] = idxs[min_loc];
263       n_local_sequential_problems++;
264     }
265     ierr = ISRestoreIndices(all_cc[i],&idxs);CHKERRQ(ierr);
266   }
267 
268   /* Number parallel problems */
269   auxglobal_parallel = 0;
270   ierr = PCBDDCSubsetNumbering(PetscObjectComm((PetscObject)graph->l2gmap),graph->l2gmap,n_local_parallel_problems,auxlocal_parallel,PETSC_NULL,&n_parallel_problems,&auxglobal_parallel);CHKERRQ(ierr);
271 
272   /* Number sequential problems */
273   auxglobal_sequential = 0;
274   ierr = PCBDDCSubsetNumbering(PetscObjectComm((PetscObject)graph->l2gmap),graph->l2gmap,n_local_sequential_problems,auxlocal_sequential,PETSC_NULL,&n_sequential_problems,&auxglobal_sequential);CHKERRQ(ierr);
275 
276   /* update info in sub_schurs */
277   if (A) {
278     ierr = PetscObjectReference((PetscObject)A);CHKERRQ(ierr);
279     sub_schurs->A = A;
280   }
281   ierr = PetscObjectReference((PetscObject)S);CHKERRQ(ierr);
282   sub_schurs->S = S;
283   ierr = PetscObjectReference((PetscObject)is_I);CHKERRQ(ierr);
284   sub_schurs->is_I = is_I;
285   ierr = PetscObjectReference((PetscObject)is_B);CHKERRQ(ierr);
286   sub_schurs->is_B = is_B;
287   sub_schurs->n_subs_seq = n_local_sequential_problems;
288   sub_schurs->n_subs_par = n_local_parallel_problems;
289   sub_schurs->n_subs_seq_g = n_sequential_problems;
290   sub_schurs->n_subs_par_g = n_parallel_problems;
291   sub_schurs->n_subs = sub_schurs->n_subs_seq + sub_schurs->n_subs_par;
292   sub_schurs->is_subs = all_cc;
293   sub_schurs->index_sequential = index_sequential;
294   sub_schurs->index_parallel = index_parallel;
295   sub_schurs->auxglobal_sequential = auxglobal_sequential;
296   sub_schurs->auxglobal_parallel = auxglobal_parallel;
297 
298   /* free workspace */
299   ierr = PetscFree(auxmapping);CHKERRQ(ierr);
300   ierr = PetscFree2(auxlocal_sequential,auxlocal_parallel);CHKERRQ(ierr);
301 
302   PetscFunctionReturn(0);
303 }
304 
305 #undef __FUNCT__
306 #define __FUNCT__ "PCBDDCSubSchursCreate"
307 PetscErrorCode PCBDDCSubSchursCreate(PCBDDCSubSchurs *sub_schurs)
308 {
309   PCBDDCSubSchurs schurs_ctx;
310   PetscErrorCode  ierr;
311 
312   PetscFunctionBegin;
313   ierr = PetscNew(&schurs_ctx);CHKERRQ(ierr);
314   schurs_ctx->n_subs = 0;
315   *sub_schurs = schurs_ctx;
316   PetscFunctionReturn(0);
317 }
318 
319 #undef __FUNCT__
320 #define __FUNCT__ "PCBDDCSubSchursDestroy"
321 PetscErrorCode PCBDDCSubSchursDestroy(PCBDDCSubSchurs *sub_schurs)
322 {
323   PetscErrorCode ierr;
324 
325   PetscFunctionBegin;
326   ierr = PCBDDCSubSchursReset(*sub_schurs);CHKERRQ(ierr);
327   ierr = PetscFree(*sub_schurs);CHKERRQ(ierr);
328   PetscFunctionReturn(0);
329 }
330 
331 #undef __FUNCT__
332 #define __FUNCT__ "PCBDDCSubSchursReset"
333 PetscErrorCode PCBDDCSubSchursReset(PCBDDCSubSchurs sub_schurs)
334 {
335   PetscInt       i;
336   PetscErrorCode ierr;
337 
338   PetscFunctionBegin;
339   ierr = MatDestroy(&sub_schurs->A);CHKERRQ(ierr);
340   ierr = MatDestroy(&sub_schurs->S);CHKERRQ(ierr);
341   ierr = ISDestroy(&sub_schurs->is_I);CHKERRQ(ierr);
342   ierr = ISDestroy(&sub_schurs->is_B);CHKERRQ(ierr);
343   ierr = MatDestroy(&sub_schurs->S_Ej_all);CHKERRQ(ierr);
344   ierr = MatDestroy(&sub_schurs->sum_S_Ej_all);CHKERRQ(ierr);
345   for (i=0;i<sub_schurs->n_subs;i++) {
346     ierr = ISDestroy(&sub_schurs->is_subs[i]);CHKERRQ(ierr);
347     ierr = ISDestroy(&sub_schurs->is_AEj_I[i]);CHKERRQ(ierr);
348     ierr = ISDestroy(&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
349     ierr = MatDestroy(&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
350     ierr = VecDestroy(&sub_schurs->work1[i]);CHKERRQ(ierr);
351     ierr = VecDestroy(&sub_schurs->work2[i]);CHKERRQ(ierr);
352   }
353   if (sub_schurs->n_subs) {
354     ierr = PetscFree(sub_schurs->is_subs);CHKERRQ(ierr);
355     ierr = PetscFree5(sub_schurs->is_AEj_I,sub_schurs->is_AEj_B,sub_schurs->S_Ej,sub_schurs->work1,sub_schurs->work2);CHKERRQ(ierr);
356     ierr = PetscFree2(sub_schurs->index_sequential,sub_schurs->index_parallel);CHKERRQ(ierr);
357     ierr = PetscFree(sub_schurs->auxglobal_sequential);CHKERRQ(ierr);
358     ierr = PetscFree(sub_schurs->auxglobal_parallel);CHKERRQ(ierr);
359   }
360   sub_schurs->n_subs = 0;
361   PetscFunctionReturn(0);
362 }
363 
364 #undef __FUNCT__
365 #define __FUNCT__ "PCBDDCAdjGetNextLayer_Private"
366 PETSC_STATIC_INLINE PetscErrorCode PCBDDCAdjGetNextLayer_Private(PetscInt* queue_tip,PetscInt n_prev,PetscBT touched,PetscInt* xadj,PetscInt* adjncy,PetscInt* n_added)
367 {
368   PetscInt       i,j,n;
369   PetscErrorCode ierr;
370 
371   PetscFunctionBegin;
372   n = 0;
373   for (i=-n_prev;i<0;i++) {
374     PetscInt start_dof = queue_tip[i];
375     for (j=xadj[start_dof];j<xadj[start_dof+1];j++) {
376       PetscInt dof = adjncy[j];
377       if (!PetscBTLookup(touched,dof)) {
378         ierr = PetscBTSet(touched,dof);CHKERRQ(ierr);
379         queue_tip[n] = dof;
380         n++;
381       }
382     }
383   }
384   *n_added = n;
385   PetscFunctionReturn(0);
386 }
387 
388 #undef __FUNCT__
389 #define __FUNCT__ "PCBDDCSubSchursSetUp"
390 PetscErrorCode PCBDDCSubSchursSetUp(PCBDDCSubSchurs sub_schurs, Mat S, IS is_A_I, IS is_A_B, PetscInt ncc, IS is_cc[], PetscInt xadj[], PetscInt adjncy[], PetscInt nlayers)
391 {
392   Mat                    A_II,A_IB,A_BI,A_BB;
393   Mat                    AE_II,*AE_IE,*AE_EI,*AE_EE;
394   IS                     is_I,*is_subset_B;
395   ISLocalToGlobalMapping BtoNmap;
396   PetscInt               i;
397   PetscBool              is_sorted;
398   PetscErrorCode         ierr;
399 
400   PetscFunctionBegin;
401   ierr = ISSorted(is_A_I,&is_sorted);CHKERRQ(ierr);
402   if (!is_sorted) {
403     SETERRQ(PetscObjectComm((PetscObject)is_A_I),PETSC_ERR_PLIB,"IS for I dofs should be shorted");
404   }
405   ierr = ISSorted(is_A_B,&is_sorted);CHKERRQ(ierr);
406   if (!is_sorted) {
407     SETERRQ(PetscObjectComm((PetscObject)is_A_B),PETSC_ERR_PLIB,"IS for B dofs should be shorted");
408   }
409 
410   /* get Schur complement matrices */
411   ierr = MatSchurComplementGetSubMatrices(S,&A_II,NULL,&A_IB,&A_BI,&A_BB);CHKERRQ(ierr);
412 
413   /* allocate space for schur complements */
414   ierr = PetscMalloc5(sub_schurs->n_subs,&sub_schurs->is_AEj_I,
415                       sub_schurs->n_subs,&sub_schurs->is_AEj_B,
416                       sub_schurs->n_subs,&sub_schurs->S_Ej,
417                       sub_schurs->n_subs,&sub_schurs->work1,
418                       sub_schurs->n_subs,&sub_schurs->work2);CHKERRQ(ierr);
419   ierr = PetscMalloc4(ncc,&is_subset_B,ncc,&AE_IE,ncc,&AE_EI,ncc,&AE_EE);CHKERRQ(ierr);
420   sub_schurs->n_subs = ncc;
421 
422   /* maps */
423   if (sub_schurs->n_subs && nlayers >= 0 && xadj != NULL && adjncy != NULL) { /* Interior problems can be different from the original one */
424     ISLocalToGlobalMapping ItoNmap;
425     PetscBT                touched;
426     const PetscInt*        idx_B;
427     PetscInt               n_I,n_B,n_local_dofs,n_prev_added,j,layer,*local_numbering;
428 
429     /* get sizes */
430     ierr = ISGetLocalSize(is_A_I,&n_I);CHKERRQ(ierr);
431     ierr = ISGetLocalSize(is_A_B,&n_B);CHKERRQ(ierr);
432 
433     ierr = ISLocalToGlobalMappingCreateIS(is_A_I,&ItoNmap);CHKERRQ(ierr);
434     ierr = PetscMalloc1(n_I+n_B,&local_numbering);CHKERRQ(ierr);
435     ierr = PetscBTCreate(n_I+n_B,&touched);CHKERRQ(ierr);
436     ierr = PetscBTMemzero(n_I+n_B,touched);CHKERRQ(ierr);
437 
438     /* all boundary dofs must be skipped when adding layers */
439     ierr = ISGetIndices(is_A_B,&idx_B);CHKERRQ(ierr);
440     for (j=0;j<n_B;j++) {
441       ierr = PetscBTSet(touched,idx_B[j]);CHKERRQ(ierr);
442     }
443     ierr = PetscMemcpy(local_numbering,idx_B,n_B*sizeof(PetscInt));CHKERRQ(ierr);
444     ierr = ISRestoreIndices(is_A_B,&idx_B);CHKERRQ(ierr);
445 
446     /* add next layers of dofs */
447     n_local_dofs = n_B;
448     n_prev_added = n_B;
449     for (layer=0;layer<nlayers;layer++) {
450       PetscInt n_added;
451       if (n_local_dofs == n_I+n_B) break;
452       if (n_local_dofs > n_I+n_B) {
453         SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Error querying layer %d. Out of bound access (%d > %d)",layer,n_local_dofs,n_I+n_B);
454       }
455       ierr = PCBDDCAdjGetNextLayer_Private(local_numbering+n_local_dofs,n_prev_added,touched,xadj,adjncy,&n_added);CHKERRQ(ierr);
456       n_prev_added = n_added;
457       n_local_dofs += n_added;
458       if (!n_added) break;
459     }
460     ierr = PetscBTDestroy(&touched);CHKERRQ(ierr);
461 
462     /* IS for I dofs in original numbering and in I numbering */
463     ierr = ISCreateGeneral(PetscObjectComm((PetscObject)ItoNmap),n_local_dofs-n_B,local_numbering+n_B,PETSC_COPY_VALUES,&sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
464     ierr = PetscFree(local_numbering);CHKERRQ(ierr);
465     ierr = ISSort(sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
466     ierr = ISGlobalToLocalMappingApplyIS(ItoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_I[0],&is_I);CHKERRQ(ierr);
467     ierr = ISLocalToGlobalMappingDestroy(&ItoNmap);CHKERRQ(ierr);
468 
469     /* II block */
470     ierr = MatGetSubMatrix(A_II,is_I,is_I,MAT_INITIAL_MATRIX,&AE_II);CHKERRQ(ierr);
471   } else {
472     PetscInt n_I;
473 
474     /* IS for I dofs in original numbering */
475     ierr = PetscObjectReference((PetscObject)is_A_I);CHKERRQ(ierr);
476     sub_schurs->is_AEj_I[0] = is_A_I;
477 
478     /* IS for I dofs in I numbering (strided 1) */
479     ierr = ISGetSize(is_A_I,&n_I);CHKERRQ(ierr);
480     ierr = ISCreateStride(PetscObjectComm((PetscObject)is_A_I),n_I,0,1,&is_I);CHKERRQ(ierr);
481 
482     /* II block is the same */
483     ierr = PetscObjectReference((PetscObject)A_II);CHKERRQ(ierr);
484     AE_II = A_II;
485   }
486 
487   /* TODO: just for compatibility with the previous version, needs to be fixed */
488   for (i=1;i<sub_schurs->n_subs;i++) {
489     ierr = PetscObjectReference((PetscObject)sub_schurs->is_AEj_I[0]);CHKERRQ(ierr);
490     sub_schurs->is_AEj_I[i] = sub_schurs->is_AEj_I[0];
491   }
492 
493   /* subsets in original and boundary numbering */
494   ierr = ISLocalToGlobalMappingCreateIS(is_A_B,&BtoNmap);CHKERRQ(ierr);
495   for (i=0;i<sub_schurs->n_subs;i++) {
496     ierr = ISDuplicate(is_cc[i],&sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
497     ierr = ISSort(sub_schurs->is_AEj_B[i]);CHKERRQ(ierr);
498     ierr = ISGlobalToLocalMappingApplyIS(BtoNmap,IS_GTOLM_DROP,sub_schurs->is_AEj_B[i],&is_subset_B[i]);CHKERRQ(ierr);
499   }
500   ierr = ISLocalToGlobalMappingDestroy(&BtoNmap);CHKERRQ(ierr);
501 
502   /* EE block */
503   for (i=0;i<sub_schurs->n_subs;i++) {
504     ierr = MatGetSubMatrix(A_BB,is_subset_B[i],is_subset_B[i],MAT_INITIAL_MATRIX,&AE_EE[i]);CHKERRQ(ierr);
505   }
506   /* IE block */
507   for (i=0;i<sub_schurs->n_subs;i++) {
508     ierr = MatGetSubMatrix(A_IB,is_I,is_subset_B[i],MAT_INITIAL_MATRIX,&AE_IE[i]);CHKERRQ(ierr);
509   }
510   /* EI block */
511   for (i=0;i<sub_schurs->n_subs;i++) {
512     ierr = MatGetSubMatrix(A_BI,is_subset_B[i],is_I,MAT_INITIAL_MATRIX,&AE_EI[i]);CHKERRQ(ierr);
513   }
514 
515   /* setup Schur complements on subset */
516   for (i=0;i<sub_schurs->n_subs;i++) {
517     ierr = MatCreateSchurComplement(AE_II,AE_II,AE_IE[i],AE_EI[i],AE_EE[i],&sub_schurs->S_Ej[i]);CHKERRQ(ierr);
518     ierr = MatCreateVecs(sub_schurs->S_Ej[i],&sub_schurs->work1[i],&sub_schurs->work2[i]);CHKERRQ(ierr);
519     if (AE_II == A_II) { /* we can reuse the same ksp */
520       KSP ksp;
521       ierr = MatSchurComplementGetKSP(S,&ksp);CHKERRQ(ierr);
522       ierr = MatSchurComplementSetKSP(sub_schurs->S_Ej[i],ksp);CHKERRQ(ierr);
523     } else { /* build new ksp object which inherits ksp and pc types from the original one */
524       KSP      origksp,schurksp;
525       PC       origpc,schurpc;
526       KSPType  ksp_type;
527       PCType   pc_type;
528       PetscInt n_internal;
529 
530       ierr = MatSchurComplementGetKSP(S,&origksp);CHKERRQ(ierr);
531       ierr = MatSchurComplementGetKSP(sub_schurs->S_Ej[i],&schurksp);CHKERRQ(ierr);
532       ierr = KSPGetType(origksp,&ksp_type);CHKERRQ(ierr);
533       ierr = KSPSetType(schurksp,ksp_type);CHKERRQ(ierr);
534       ierr = KSPGetPC(schurksp,&schurpc);CHKERRQ(ierr);
535       ierr = KSPGetPC(origksp,&origpc);CHKERRQ(ierr);
536       ierr = PCGetType(origpc,&pc_type);CHKERRQ(ierr);
537       ierr = PCSetType(schurpc,pc_type);CHKERRQ(ierr);
538       ierr = ISGetSize(is_I,&n_internal);CHKERRQ(ierr);
539       if (n_internal) { /* UMFPACK gives error with 0 sized problems */
540         MatSolverPackage solver=NULL;
541         ierr = PCFactorGetMatSolverPackage(origpc,(const MatSolverPackage*)&solver);CHKERRQ(ierr);
542         if (solver) {
543           ierr = PCFactorSetMatSolverPackage(schurpc,solver);CHKERRQ(ierr);
544         }
545       }
546       ierr = KSPSetUp(schurksp);CHKERRQ(ierr);
547     }
548   }
549   /* free */
550   ierr = ISDestroy(&is_I);CHKERRQ(ierr);
551   ierr = MatDestroy(&AE_II);CHKERRQ(ierr);
552   for (i=0;i<sub_schurs->n_subs;i++) {
553     ierr = MatDestroy(&AE_EE[i]);CHKERRQ(ierr);
554     ierr = MatDestroy(&AE_IE[i]);CHKERRQ(ierr);
555     ierr = MatDestroy(&AE_EI[i]);CHKERRQ(ierr);
556     ierr = ISDestroy(&is_subset_B[i]);CHKERRQ(ierr);
557   }
558   ierr = PetscFree4(is_subset_B,AE_IE,AE_EI,AE_EE);CHKERRQ(ierr);
559   PetscFunctionReturn(0);
560 }
561