xref: /petsc/src/dm/impls/plex/plexorient.c (revision f97672e55eacc8688507b9471cd7ec2664d7f203)
1 #include <petsc/private/dmpleximpl.h>   /*I      "petscdmplex.h"   I*/
2 #include <petscsf.h>
3 
4 /*@
5   DMPlexOrientPoint - Act with the given orientation on the cone points of this mesh point, and update its use in the mesh.
6 
7   Not Collective
8 
9   Input Parameters:
10 + dm - The DM
11 . p  - The mesh point
12 - o  - The orientation
13 
14   Level: intermediate
15 
16 .seealso: `DMPlexOrient()`, `DMPlexGetCone()`, `DMPlexGetConeOrientation()`, `DMPlexInterpolate()`, `DMPlexGetChart()`
17 @*/
18 PetscErrorCode DMPlexOrientPoint(DM dm, PetscInt p, PetscInt o)
19 {
20   DMPolytopeType  ct;
21   const PetscInt *arr, *cone, *ornt, *support;
22   PetscInt       *newcone, *newornt;
23   PetscInt        coneSize, c, supportSize, s;
24 
25   PetscFunctionBegin;
26   PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
27   PetscCall(DMPlexGetCellType(dm, p, &ct));
28   arr  = DMPolytopeTypeGetArrangment(ct, o);
29   PetscCall(DMPlexGetConeSize(dm, p, &coneSize));
30   PetscCall(DMPlexGetCone(dm, p, &cone));
31   PetscCall(DMPlexGetConeOrientation(dm, p, &ornt));
32   PetscCall(DMGetWorkArray(dm, coneSize, MPIU_INT, &newcone));
33   PetscCall(DMGetWorkArray(dm, coneSize, MPIU_INT, &newornt));
34   for (c = 0; c < coneSize; ++c) {
35     DMPolytopeType ft;
36     PetscInt       nO;
37 
38     PetscCall(DMPlexGetCellType(dm, cone[c], &ft));
39     nO   = DMPolytopeTypeGetNumArrangments(ft)/2;
40     newcone[c] = cone[arr[c*2+0]];
41     newornt[c] = DMPolytopeTypeComposeOrientation(ft, arr[c*2+1], ornt[arr[c*2+0]]);
42     PetscCheck(!newornt[c] || !(newornt[c] >= nO || newornt[c] < -nO),PETSC_COMM_SELF, PETSC_ERR_PLIB, "Invalid orientation %" PetscInt_FMT " not in [%" PetscInt_FMT ",%" PetscInt_FMT ") for %s %" PetscInt_FMT, newornt[c], -nO, nO, DMPolytopeTypes[ft], cone[c]);
43   }
44   PetscCall(DMPlexSetCone(dm, p, newcone));
45   PetscCall(DMPlexSetConeOrientation(dm, p, newornt));
46   PetscCall(DMRestoreWorkArray(dm, coneSize, MPIU_INT, &newcone));
47   PetscCall(DMRestoreWorkArray(dm, coneSize, MPIU_INT, &newornt));
48   /* Update orientation of this point in the support points */
49   PetscCall(DMPlexGetSupportSize(dm, p, &supportSize));
50   PetscCall(DMPlexGetSupport(dm, p, &support));
51   for (s = 0; s < supportSize; ++s) {
52     PetscCall(DMPlexGetConeSize(dm, support[s], &coneSize));
53     PetscCall(DMPlexGetCone(dm, support[s], &cone));
54     PetscCall(DMPlexGetConeOrientation(dm, support[s], &ornt));
55     for (c = 0; c < coneSize; ++c) {
56       PetscInt po;
57 
58       if (cone[c] != p) continue;
59       /* ornt[c] * 0 = target = po * o so that po = ornt[c] * o^{-1} */
60       po   = DMPolytopeTypeComposeOrientationInv(ct, ornt[c], o);
61       PetscCall(DMPlexInsertConeOrientation(dm, support[s], c, po));
62     }
63   }
64   PetscFunctionReturn(0);
65 }
66 
67 /*
68   - Checks face match
69     - Flips non-matching
70   - Inserts faces of support cells in FIFO
71 */
72 static PetscErrorCode DMPlexCheckFace_Internal(DM dm, PetscInt *faceFIFO, PetscInt *fTop, PetscInt *fBottom, PetscInt cStart, PetscInt fStart, PetscInt fEnd, PetscBT seenCells, PetscBT flippedCells, PetscBT seenFaces)
73 {
74   const PetscInt *support, *coneA, *coneB, *coneOA, *coneOB;
75   PetscInt        supportSize, coneSizeA, coneSizeB, posA = -1, posB = -1;
76   PetscInt        face, dim, seenA, flippedA, seenB, flippedB, mismatch, c;
77 
78   PetscFunctionBegin;
79   face = faceFIFO[(*fTop)++];
80   PetscCall(DMGetDimension(dm, &dim));
81   PetscCall(DMPlexGetSupportSize(dm, face, &supportSize));
82   PetscCall(DMPlexGetSupport(dm, face, &support));
83   if (supportSize < 2) PetscFunctionReturn(0);
84   PetscCheck(supportSize == 2,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Faces should separate only two cells, not %" PetscInt_FMT, supportSize);
85   seenA    = PetscBTLookup(seenCells,    support[0]-cStart);
86   flippedA = PetscBTLookup(flippedCells, support[0]-cStart) ? 1 : 0;
87   seenB    = PetscBTLookup(seenCells,    support[1]-cStart);
88   flippedB = PetscBTLookup(flippedCells, support[1]-cStart) ? 1 : 0;
89 
90   PetscCall(DMPlexGetConeSize(dm, support[0], &coneSizeA));
91   PetscCall(DMPlexGetConeSize(dm, support[1], &coneSizeB));
92   PetscCall(DMPlexGetCone(dm, support[0], &coneA));
93   PetscCall(DMPlexGetCone(dm, support[1], &coneB));
94   PetscCall(DMPlexGetConeOrientation(dm, support[0], &coneOA));
95   PetscCall(DMPlexGetConeOrientation(dm, support[1], &coneOB));
96   for (c = 0; c < coneSizeA; ++c) {
97     if (!PetscBTLookup(seenFaces, coneA[c]-fStart)) {
98       faceFIFO[(*fBottom)++] = coneA[c];
99       PetscCall(PetscBTSet(seenFaces, coneA[c]-fStart));
100     }
101     if (coneA[c] == face) posA = c;
102     PetscCheck(*fBottom <= fEnd-fStart,PETSC_COMM_SELF, PETSC_ERR_PLIB, "Face %" PetscInt_FMT " was pushed exceeding capacity %" PetscInt_FMT " > %" PetscInt_FMT, coneA[c], *fBottom, fEnd-fStart);
103   }
104   PetscCheck(posA >= 0,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Face %" PetscInt_FMT " could not be located in cell %" PetscInt_FMT, face, support[0]);
105   for (c = 0; c < coneSizeB; ++c) {
106     if (!PetscBTLookup(seenFaces, coneB[c]-fStart)) {
107       faceFIFO[(*fBottom)++] = coneB[c];
108       PetscCall(PetscBTSet(seenFaces, coneB[c]-fStart));
109     }
110     if (coneB[c] == face) posB = c;
111     PetscCheck(*fBottom <= fEnd-fStart,PETSC_COMM_SELF, PETSC_ERR_PLIB, "Face %" PetscInt_FMT " was pushed exceeding capacity %" PetscInt_FMT " > %" PetscInt_FMT, coneA[c], *fBottom, fEnd-fStart);
112   }
113   PetscCheck(posB >= 0,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Face %" PetscInt_FMT " could not be located in cell %" PetscInt_FMT, face, support[1]);
114 
115   if (dim == 1) {
116     mismatch = posA == posB;
117   } else {
118     mismatch = coneOA[posA] == coneOB[posB];
119   }
120 
121   if (mismatch ^ (flippedA ^ flippedB)) {
122     PetscCheck(!seenA || !seenB,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Previously seen cells %" PetscInt_FMT " and %" PetscInt_FMT " do not match: Fault mesh is non-orientable", support[0], support[1]);
123     if (!seenA && !flippedA) {
124       PetscCall(PetscBTSet(flippedCells, support[0]-cStart));
125     } else if (!seenB && !flippedB) {
126       PetscCall(PetscBTSet(flippedCells, support[1]-cStart));
127     } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Inconsistent mesh orientation: Fault mesh is non-orientable");
128   } else PetscCheck(!mismatch || !flippedA || !flippedB,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Attempt to flip already flipped cell: Fault mesh is non-orientable");
129   PetscCall(PetscBTSet(seenCells, support[0]-cStart));
130   PetscCall(PetscBTSet(seenCells, support[1]-cStart));
131   PetscFunctionReturn(0);
132 }
133 
134 /*@
135   DMPlexOrient - Give a consistent orientation to the input mesh
136 
137   Input Parameters:
138 . dm - The DM
139 
140   Note: The orientation data for the DM are change in-place.
141 $ This routine will fail for non-orientable surfaces, such as the Moebius strip.
142 
143   Level: advanced
144 
145 .seealso: `DMCreate()`, `DMPLEX`
146 @*/
147 PetscErrorCode DMPlexOrient(DM dm)
148 {
149   MPI_Comm           comm;
150   PetscSF            sf;
151   const PetscInt    *lpoints;
152   const PetscSFNode *rpoints;
153   PetscSFNode       *rorntComp = NULL, *lorntComp = NULL;
154   PetscInt          *numNeighbors, **neighbors, *locSupport = NULL;
155   PetscSFNode       *nrankComp;
156   PetscBool         *match, *flipped;
157   PetscBT            seenCells, flippedCells, seenFaces;
158   PetscInt          *faceFIFO, fTop, fBottom, *cellComp, *faceComp;
159   PetscInt           numLeaves, numRoots, dim, h, cStart, cEnd, c, cell, fStart, fEnd, face, off, totNeighbors = 0;
160   PetscMPIInt        rank, size, numComponents, comp = 0;
161   PetscBool          flg, flg2;
162   PetscViewer        viewer = NULL, selfviewer = NULL;
163 
164   PetscFunctionBegin;
165   PetscCall(PetscObjectGetComm((PetscObject) dm, &comm));
166   PetscCallMPI(MPI_Comm_rank(comm, &rank));
167   PetscCallMPI(MPI_Comm_size(comm, &size));
168   PetscCall(PetscOptionsHasName(((PetscObject) dm)->options,((PetscObject) dm)->prefix, "-orientation_view", &flg));
169   PetscCall(PetscOptionsHasName(((PetscObject) dm)->options,((PetscObject) dm)->prefix, "-orientation_view_synchronized", &flg2));
170   PetscCall(DMGetPointSF(dm, &sf));
171   PetscCall(PetscSFGetGraph(sf, &numRoots, &numLeaves, &lpoints, &rpoints));
172   /* Truth Table
173      mismatch    flips   do action   mismatch   flipA ^ flipB   action
174          F       0 flips     no         F             F           F
175          F       1 flip      yes        F             T           T
176          F       2 flips     no         T             F           T
177          T       0 flips     yes        T             T           F
178          T       1 flip      no
179          T       2 flips     yes
180   */
181   PetscCall(DMGetDimension(dm, &dim));
182   PetscCall(DMPlexGetVTKCellHeight(dm, &h));
183   PetscCall(DMPlexGetHeightStratum(dm, h,   &cStart, &cEnd));
184   PetscCall(DMPlexGetHeightStratum(dm, h+1, &fStart, &fEnd));
185   PetscCall(PetscBTCreate(cEnd - cStart, &seenCells));
186   PetscCall(PetscBTMemzero(cEnd - cStart, seenCells));
187   PetscCall(PetscBTCreate(cEnd - cStart, &flippedCells));
188   PetscCall(PetscBTMemzero(cEnd - cStart, flippedCells));
189   PetscCall(PetscBTCreate(fEnd - fStart, &seenFaces));
190   PetscCall(PetscBTMemzero(fEnd - fStart, seenFaces));
191   PetscCall(PetscCalloc3(fEnd - fStart, &faceFIFO, cEnd-cStart, &cellComp, fEnd-fStart, &faceComp));
192   /*
193    OLD STYLE
194    - Add an integer array over cells and faces (component) for connected component number
195    Foreach component
196      - Mark the initial cell as seen
197      - Process component as usual
198      - Set component for all seenCells
199      - Wipe seenCells and seenFaces (flippedCells can stay)
200    - Generate parallel adjacency for component using SF and seenFaces
201    - Collect numComponents adj data from each proc to 0
202    - Build same serial graph
203    - Use same solver
204    - Use Scatterv to to send back flipped flags for each component
205    - Negate flippedCells by component
206 
207    NEW STYLE
208    - Create the adj on each process
209    - Bootstrap to complete graph on proc 0
210   */
211   /* Loop over components */
212   for (cell = cStart; cell < cEnd; ++cell) cellComp[cell-cStart] = -1;
213   do {
214     /* Look for first unmarked cell */
215     for (cell = cStart; cell < cEnd; ++cell) if (cellComp[cell-cStart] < 0) break;
216     if (cell >= cEnd) break;
217     /* Initialize FIFO with first cell in component */
218     {
219       const PetscInt *cone;
220       PetscInt        coneSize;
221 
222       fTop = fBottom = 0;
223       PetscCall(DMPlexGetConeSize(dm, cell, &coneSize));
224       PetscCall(DMPlexGetCone(dm, cell, &cone));
225       for (c = 0; c < coneSize; ++c) {
226         faceFIFO[fBottom++] = cone[c];
227         PetscCall(PetscBTSet(seenFaces, cone[c]-fStart));
228       }
229       PetscCall(PetscBTSet(seenCells, cell-cStart));
230     }
231     /* Consider each face in FIFO */
232     while (fTop < fBottom) {
233       PetscCall(DMPlexCheckFace_Internal(dm, faceFIFO, &fTop, &fBottom, cStart, fStart, fEnd, seenCells, flippedCells, seenFaces));
234     }
235     /* Set component for cells and faces */
236     for (cell = 0; cell < cEnd-cStart; ++cell) {
237       if (PetscBTLookup(seenCells, cell)) cellComp[cell] = comp;
238     }
239     for (face = 0; face < fEnd-fStart; ++face) {
240       if (PetscBTLookup(seenFaces, face)) faceComp[face] = comp;
241     }
242     /* Wipe seenCells and seenFaces for next component */
243     PetscCall(PetscBTMemzero(fEnd - fStart, seenFaces));
244     PetscCall(PetscBTMemzero(cEnd - cStart, seenCells));
245     ++comp;
246   } while (1);
247   numComponents = comp;
248   if (flg) {
249     PetscViewer v;
250 
251     PetscCall(PetscViewerASCIIGetStdout(comm, &v));
252     PetscCall(PetscViewerASCIIPushSynchronized(v));
253     PetscCall(PetscViewerASCIISynchronizedPrintf(v, "[%d]BT for serial flipped cells:\n", rank));
254     PetscCall(PetscBTView(cEnd-cStart, flippedCells, v));
255     PetscCall(PetscViewerFlush(v));
256     PetscCall(PetscViewerASCIIPopSynchronized(v));
257   }
258   /* Now all subdomains are oriented, but we need a consistent parallel orientation */
259   if (numLeaves >= 0) {
260     PetscInt maxSupportSize, neighbor;
261 
262     /* Store orientations of boundary faces*/
263     PetscCall(DMPlexGetMaxSizes(dm, NULL, &maxSupportSize));
264     PetscCall(PetscCalloc3(numRoots, &rorntComp, numRoots, &lorntComp, maxSupportSize, &locSupport));
265     for (face = fStart; face < fEnd; ++face) {
266       const PetscInt *cone, *support, *ornt;
267       PetscInt        coneSize, supportSize, Ns = 0, s, l;
268 
269       PetscCall(DMPlexGetSupportSize(dm, face, &supportSize));
270       /* Ignore overlapping cells */
271       PetscCall(DMPlexGetSupport(dm, face, &support));
272       for (s = 0; s < supportSize; ++s) {
273         PetscCall(PetscFindInt(support[s], numLeaves, lpoints, &l));
274         if (l >= 0) continue;
275         locSupport[Ns++] = support[s];
276       }
277       if (Ns != 1) continue;
278       neighbor = locSupport[0];
279       PetscCall(DMPlexGetCone(dm, neighbor, &cone));
280       PetscCall(DMPlexGetConeSize(dm, neighbor, &coneSize));
281       PetscCall(DMPlexGetConeOrientation(dm, neighbor, &ornt));
282       for (c = 0; c < coneSize; ++c) if (cone[c] == face) break;
283       if (dim == 1) {
284         /* Use cone position instead, shifted to -1 or 1 */
285         if (PetscBTLookup(flippedCells, neighbor-cStart)) rorntComp[face].rank = 1-c*2;
286         else                                              rorntComp[face].rank = c*2-1;
287       } else {
288         if (PetscBTLookup(flippedCells, neighbor-cStart)) rorntComp[face].rank = ornt[c] < 0 ? -1 :  1;
289         else                                              rorntComp[face].rank = ornt[c] < 0 ?  1 : -1;
290       }
291       rorntComp[face].index = faceComp[face-fStart];
292     }
293     /* Communicate boundary edge orientations */
294     PetscCall(PetscSFBcastBegin(sf, MPIU_2INT, rorntComp, lorntComp,MPI_REPLACE));
295     PetscCall(PetscSFBcastEnd(sf, MPIU_2INT, rorntComp, lorntComp,MPI_REPLACE));
296   }
297   /* Get process adjacency */
298   PetscCall(PetscMalloc2(numComponents, &numNeighbors, numComponents, &neighbors));
299   viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)dm));
300   if (flg2) PetscCall(PetscViewerASCIIPushSynchronized(viewer));
301   PetscCall(PetscViewerGetSubViewer(viewer,PETSC_COMM_SELF,&selfviewer));
302   for (comp = 0; comp < numComponents; ++comp) {
303     PetscInt  l, n;
304 
305     numNeighbors[comp] = 0;
306     PetscCall(PetscMalloc1(PetscMax(numLeaves, 0), &neighbors[comp]));
307     /* I know this is p^2 time in general, but for bounded degree its alright */
308     for (l = 0; l < numLeaves; ++l) {
309       const PetscInt face = lpoints[l];
310 
311       /* Find a representative face (edge) separating pairs of procs */
312       if ((face >= fStart) && (face < fEnd) && (faceComp[face-fStart] == comp) && rorntComp[face].rank) {
313         const PetscInt rrank = rpoints[l].rank;
314         const PetscInt rcomp = lorntComp[face].index;
315 
316         for (n = 0; n < numNeighbors[comp]; ++n) if ((rrank == rpoints[neighbors[comp][n]].rank) && (rcomp == lorntComp[lpoints[neighbors[comp][n]]].index)) break;
317         if (n >= numNeighbors[comp]) {
318           PetscInt supportSize;
319 
320           PetscCall(DMPlexGetSupportSize(dm, face, &supportSize));
321           PetscCheck(supportSize == 1,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Boundary faces should see one cell, not %" PetscInt_FMT, supportSize);
322           if (flg) PetscCall(PetscViewerASCIIPrintf(selfviewer, "[%d]: component %d, Found representative leaf %" PetscInt_FMT " (face %" PetscInt_FMT ") connecting to face %" PetscInt_FMT " on (%" PetscInt_FMT ", %" PetscInt_FMT ") with orientation %" PetscInt_FMT "\n", rank, comp, l, face, rpoints[l].index, rrank, rcomp, lorntComp[face].rank));
323           neighbors[comp][numNeighbors[comp]++] = l;
324         }
325       }
326     }
327     totNeighbors += numNeighbors[comp];
328   }
329   PetscCall(PetscViewerRestoreSubViewer(viewer,PETSC_COMM_SELF,&selfviewer));
330   PetscCall(PetscViewerFlush(viewer));
331   if (flg2) PetscCall(PetscViewerASCIIPopSynchronized(viewer));
332   PetscCall(PetscMalloc2(totNeighbors, &nrankComp, totNeighbors, &match));
333   for (comp = 0, off = 0; comp < numComponents; ++comp) {
334     PetscInt n;
335 
336     for (n = 0; n < numNeighbors[comp]; ++n, ++off) {
337       const PetscInt face = lpoints[neighbors[comp][n]];
338       const PetscInt o    = rorntComp[face].rank*lorntComp[face].rank;
339 
340       if      (o < 0) match[off] = PETSC_TRUE;
341       else if (o > 0) match[off] = PETSC_FALSE;
342       else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid face %" PetscInt_FMT " (%" PetscInt_FMT ", %" PetscInt_FMT ") neighbor: %" PetscInt_FMT " comp: %d", face, rorntComp[face].rank, lorntComp[face].rank, neighbors[comp][n], comp);
343       nrankComp[off].rank  = rpoints[neighbors[comp][n]].rank;
344       nrankComp[off].index = lorntComp[lpoints[neighbors[comp][n]]].index;
345     }
346     PetscCall(PetscFree(neighbors[comp]));
347   }
348   /* Collect the graph on 0 */
349   if (numLeaves >= 0) {
350     Mat          G;
351     PetscBT      seenProcs, flippedProcs;
352     PetscInt    *procFIFO, pTop, pBottom;
353     PetscInt    *N   = NULL, *Noff;
354     PetscSFNode *adj = NULL;
355     PetscBool   *val = NULL;
356     PetscMPIInt *recvcounts = NULL, *displs = NULL, *Nc, p, o;
357     PetscMPIInt  size = 0;
358 
359     PetscCall(PetscCalloc1(numComponents, &flipped));
360     if (rank == 0) PetscCallMPI(MPI_Comm_size(comm, &size));
361     PetscCall(PetscCalloc4(size, &recvcounts, size+1, &displs, size, &Nc, size+1, &Noff));
362     PetscCallMPI(MPI_Gather(&numComponents, 1, MPI_INT, Nc, 1, MPI_INT, 0, comm));
363     for (p = 0; p < size; ++p) {
364       displs[p+1] = displs[p] + Nc[p];
365     }
366     if (rank == 0) PetscCall(PetscMalloc1(displs[size],&N));
367     PetscCallMPI(MPI_Gatherv(numNeighbors, numComponents, MPIU_INT, N, Nc, displs, MPIU_INT, 0, comm));
368     for (p = 0, o = 0; p < size; ++p) {
369       recvcounts[p] = 0;
370       for (c = 0; c < Nc[p]; ++c, ++o) recvcounts[p] += N[o];
371       displs[p+1] = displs[p] + recvcounts[p];
372     }
373     if (rank == 0) PetscCall(PetscMalloc2(displs[size], &adj, displs[size], &val));
374     PetscCallMPI(MPI_Gatherv(nrankComp, totNeighbors, MPIU_2INT, adj, recvcounts, displs, MPIU_2INT, 0, comm));
375     PetscCallMPI(MPI_Gatherv(match, totNeighbors, MPIU_BOOL, val, recvcounts, displs, MPIU_BOOL, 0, comm));
376     PetscCall(PetscFree2(numNeighbors, neighbors));
377     if (rank == 0) {
378       for (p = 1; p <= size; ++p) {Noff[p] = Noff[p-1] + Nc[p-1];}
379       if (flg) {
380         PetscInt n;
381 
382         for (p = 0, off = 0; p < size; ++p) {
383           for (c = 0; c < Nc[p]; ++c) {
384             PetscCall(PetscPrintf(PETSC_COMM_SELF, "Proc %d Comp %" PetscInt_FMT ":\n", p, c));
385             for (n = 0; n < N[Noff[p]+c]; ++n, ++off) {
386               PetscCall(PetscPrintf(PETSC_COMM_SELF, "  edge (%" PetscInt_FMT ", %" PetscInt_FMT ") (%s):\n", adj[off].rank, adj[off].index, PetscBools[val[off]]));
387             }
388           }
389         }
390       }
391       /* Symmetrize the graph */
392       PetscCall(MatCreate(PETSC_COMM_SELF, &G));
393       PetscCall(MatSetSizes(G, Noff[size], Noff[size], Noff[size], Noff[size]));
394       PetscCall(MatSetUp(G));
395       for (p = 0, off = 0; p < size; ++p) {
396         for (c = 0; c < Nc[p]; ++c) {
397           const PetscInt r = Noff[p]+c;
398           PetscInt       n;
399 
400           for (n = 0; n < N[r]; ++n, ++off) {
401             const PetscInt    q = Noff[adj[off].rank] + adj[off].index;
402             const PetscScalar o = val[off] ? 1.0 : 0.0;
403 
404             PetscCall(MatSetValues(G, 1, &r, 1, &q, &o, INSERT_VALUES));
405             PetscCall(MatSetValues(G, 1, &q, 1, &r, &o, INSERT_VALUES));
406           }
407         }
408       }
409       PetscCall(MatAssemblyBegin(G, MAT_FINAL_ASSEMBLY));
410       PetscCall(MatAssemblyEnd(G, MAT_FINAL_ASSEMBLY));
411 
412       PetscCall(PetscBTCreate(Noff[size], &seenProcs));
413       PetscCall(PetscBTMemzero(Noff[size], seenProcs));
414       PetscCall(PetscBTCreate(Noff[size], &flippedProcs));
415       PetscCall(PetscBTMemzero(Noff[size], flippedProcs));
416       PetscCall(PetscMalloc1(Noff[size], &procFIFO));
417       pTop = pBottom = 0;
418       for (p = 0; p < Noff[size]; ++p) {
419         if (PetscBTLookup(seenProcs, p)) continue;
420         /* Initialize FIFO with next proc */
421         procFIFO[pBottom++] = p;
422         PetscCall(PetscBTSet(seenProcs, p));
423         /* Consider each proc in FIFO */
424         while (pTop < pBottom) {
425           const PetscScalar *ornt;
426           const PetscInt    *neighbors;
427           PetscInt           proc, nproc, seen, flippedA, flippedB, mismatch, numNeighbors, n;
428 
429           proc     = procFIFO[pTop++];
430           flippedA = PetscBTLookup(flippedProcs, proc) ? 1 : 0;
431           PetscCall(MatGetRow(G, proc, &numNeighbors, &neighbors, &ornt));
432           /* Loop over neighboring procs */
433           for (n = 0; n < numNeighbors; ++n) {
434             nproc    = neighbors[n];
435             mismatch = PetscRealPart(ornt[n]) > 0.5 ? 0 : 1;
436             seen     = PetscBTLookup(seenProcs, nproc);
437             flippedB = PetscBTLookup(flippedProcs, nproc) ? 1 : 0;
438 
439             if (mismatch ^ (flippedA ^ flippedB)) {
440               PetscCheck(!seen,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Previously seen procs %" PetscInt_FMT " and %" PetscInt_FMT " do not match: Fault mesh is non-orientable", proc, nproc);
441               if (!flippedB) {
442                 PetscCall(PetscBTSet(flippedProcs, nproc));
443               } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Inconsistent mesh orientation: Fault mesh is non-orientable");
444             } else PetscCheck(!mismatch || !flippedA || !flippedB,PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Attempt to flip already flipped cell: Fault mesh is non-orientable");
445             if (!seen) {
446               procFIFO[pBottom++] = nproc;
447               PetscCall(PetscBTSet(seenProcs, nproc));
448             }
449           }
450         }
451       }
452       PetscCall(PetscFree(procFIFO));
453       PetscCall(MatDestroy(&G));
454       PetscCall(PetscFree2(adj, val));
455       PetscCall(PetscBTDestroy(&seenProcs));
456     }
457     /* Scatter flip flags */
458     {
459       PetscBool *flips = NULL;
460 
461       if (rank == 0) {
462         PetscCall(PetscMalloc1(Noff[size], &flips));
463         for (p = 0; p < Noff[size]; ++p) {
464           flips[p] = PetscBTLookup(flippedProcs, p) ? PETSC_TRUE : PETSC_FALSE;
465           if (flg && flips[p]) PetscCall(PetscPrintf(comm, "Flipping Proc+Comp %d:\n", p));
466         }
467         for (p = 0; p < size; ++p) {
468           displs[p+1] = displs[p] + Nc[p];
469         }
470       }
471       PetscCallMPI(MPI_Scatterv(flips, Nc, displs, MPIU_BOOL, flipped, numComponents, MPIU_BOOL, 0, comm));
472       PetscCall(PetscFree(flips));
473     }
474     if (rank == 0) PetscCall(PetscBTDestroy(&flippedProcs));
475     PetscCall(PetscFree(N));
476     PetscCall(PetscFree4(recvcounts, displs, Nc, Noff));
477     PetscCall(PetscFree2(nrankComp, match));
478 
479     /* Decide whether to flip cells in each component */
480     for (c = 0; c < cEnd-cStart; ++c) {if (flipped[cellComp[c]]) PetscCall(PetscBTNegate(flippedCells, c));}
481     PetscCall(PetscFree(flipped));
482   }
483   if (flg) {
484     PetscViewer v;
485 
486     PetscCall(PetscViewerASCIIGetStdout(comm, &v));
487     PetscCall(PetscViewerASCIIPushSynchronized(v));
488     PetscCall(PetscViewerASCIISynchronizedPrintf(v, "[%d]BT for parallel flipped cells:\n", rank));
489     PetscCall(PetscBTView(cEnd-cStart, flippedCells, v));
490     PetscCall(PetscViewerFlush(v));
491     PetscCall(PetscViewerASCIIPopSynchronized(v));
492   }
493   /* Reverse flipped cells in the mesh */
494   for (c = cStart; c < cEnd; ++c) {
495     if (PetscBTLookup(flippedCells, c-cStart)) {
496       PetscCall(DMPlexOrientPoint(dm, c, -1));
497     }
498   }
499   PetscCall(PetscBTDestroy(&seenCells));
500   PetscCall(PetscBTDestroy(&flippedCells));
501   PetscCall(PetscBTDestroy(&seenFaces));
502   PetscCall(PetscFree2(numNeighbors, neighbors));
503   PetscCall(PetscFree3(rorntComp, lorntComp, locSupport));
504   PetscCall(PetscFree3(faceFIFO, cellComp, faceComp));
505   PetscFunctionReturn(0);
506 }
507