Actual source code: partptscotch.c

      1: #include <petsc/private/partitionerimpl.h>

      3: #if defined(PETSC_HAVE_PTSCOTCH)
      4: EXTERN_C_BEGIN
      5: #include <ptscotch.h>
      6: EXTERN_C_END
      7: #endif

      9: PetscBool  PTScotchPartitionerCite = PETSC_FALSE;
     10: const char PTScotchPartitionerCitation[] =
     11:   "@article{PTSCOTCH,\n"
     12:   "  author  = {C. Chevalier and F. Pellegrini},\n"
     13:   "  title   = {{PT-SCOTCH}: a tool for efficient parallel graph ordering},\n"
     14:   "  journal = {Parallel Computing},\n"
     15:   "  volume  = {34},\n"
     16:   "  number  = {6},\n"
     17:   "  pages   = {318--331},\n"
     18:   "  year    = {2008},\n"
     19:   "  doi     = {https://doi.org/10.1016/j.parco.2007.12.001}\n"
     20:   "}\n";

     22: typedef struct {
     23:   MPI_Comm  pcomm;
     24:   PetscInt  strategy;
     25:   PetscReal imbalance;
     26: } PetscPartitioner_PTScotch;

     28: #if defined(PETSC_HAVE_PTSCOTCH)

     32: static int PTScotch_Strategy(PetscInt strategy)
     33: {
     34:   switch (strategy) {
     35:   case  0: return SCOTCH_STRATDEFAULT;
     36:   case  1: return SCOTCH_STRATQUALITY;
     37:   case  2: return SCOTCH_STRATSPEED;
     38:   case  3: return SCOTCH_STRATBALANCE;
     39:   case  4: return SCOTCH_STRATSAFETY;
     40:   case  5: return SCOTCH_STRATSCALABILITY;
     41:   case  6: return SCOTCH_STRATRECURSIVE;
     42:   case  7: return SCOTCH_STRATREMAP;
     43:   default: return SCOTCH_STRATDEFAULT;
     44:   }
     45: }

     47: static PetscErrorCode PTScotch_PartGraph_Seq(SCOTCH_Num strategy, double imbalance, SCOTCH_Num n, SCOTCH_Num xadj[], SCOTCH_Num adjncy[],
     48:                                              SCOTCH_Num vtxwgt[], SCOTCH_Num adjwgt[], SCOTCH_Num nparts, SCOTCH_Num tpart[], SCOTCH_Num part[])
     49: {
     50:   SCOTCH_Arch    archdat;
     51:   SCOTCH_Graph   grafdat;
     52:   SCOTCH_Strat   stradat;
     53:   SCOTCH_Num     vertnbr = n;
     54:   SCOTCH_Num     edgenbr = xadj[n];
     55:   SCOTCH_Num*    velotab = vtxwgt;
     56:   SCOTCH_Num*    edlotab = adjwgt;
     57:   SCOTCH_Num     flagval = strategy;
     58:   double         kbalval = imbalance;

     60:   {
     61:     PetscBool flg = PETSC_TRUE;
     62:     PetscOptionsDeprecatedNoObject("-petscpartititoner_ptscotch_vertex_weight",NULL,"3.13","Use -petscpartitioner_use_vertex_weights");
     63:     PetscOptionsGetBool(NULL, NULL, "-petscpartititoner_ptscotch_vertex_weight", &flg, NULL);
     64:     if (!flg) velotab = NULL;
     65:   }
     66:   SCOTCH_graphInit(&grafdat);
     67:   SCOTCH_graphBuild(&grafdat, 0, vertnbr, xadj, xadj + 1, velotab, NULL, edgenbr, adjncy, edlotab);
     68:   SCOTCH_stratInit(&stradat);
     69:   SCOTCH_stratGraphMapBuild(&stradat, flagval, nparts, kbalval);
     70:   SCOTCH_archInit(&archdat);
     71:   if (tpart) {
     72:     SCOTCH_archCmpltw(&archdat, nparts, tpart);
     73:   } else {
     74:     SCOTCH_archCmplt(&archdat, nparts);
     75:   }
     76:   SCOTCH_graphMap(&grafdat, &archdat, &stradat, part);
     77:   SCOTCH_archExit(&archdat);
     78:   SCOTCH_stratExit(&stradat);
     79:   SCOTCH_graphExit(&grafdat);
     80:   return 0;
     81: }

     83: static PetscErrorCode PTScotch_PartGraph_MPI(SCOTCH_Num strategy, double imbalance, SCOTCH_Num vtxdist[], SCOTCH_Num xadj[], SCOTCH_Num adjncy[],
     84:                                              SCOTCH_Num vtxwgt[], SCOTCH_Num adjwgt[], SCOTCH_Num nparts, SCOTCH_Num tpart[], SCOTCH_Num part[], MPI_Comm comm)
     85: {
     86:   PetscMPIInt     procglbnbr;
     87:   PetscMPIInt     proclocnum;
     88:   SCOTCH_Arch     archdat;
     89:   SCOTCH_Dgraph   grafdat;
     90:   SCOTCH_Dmapping mappdat;
     91:   SCOTCH_Strat    stradat;
     92:   SCOTCH_Num      vertlocnbr;
     93:   SCOTCH_Num      edgelocnbr;
     94:   SCOTCH_Num*     veloloctab = vtxwgt;
     95:   SCOTCH_Num*     edloloctab = adjwgt;
     96:   SCOTCH_Num      flagval = strategy;
     97:   double          kbalval = imbalance;

     99:   {
    100:     PetscBool flg = PETSC_TRUE;
    101:     PetscOptionsDeprecatedNoObject("-petscpartititoner_ptscotch_vertex_weight",NULL,"3.13","Use -petscpartitioner_use_vertex_weights");
    102:     PetscOptionsGetBool(NULL, NULL, "-petscpartititoner_ptscotch_vertex_weight", &flg, NULL);
    103:     if (!flg) veloloctab = NULL;
    104:   }
    105:   MPI_Comm_size(comm, &procglbnbr);
    106:   MPI_Comm_rank(comm, &proclocnum);
    107:   vertlocnbr = vtxdist[proclocnum + 1] - vtxdist[proclocnum];
    108:   edgelocnbr = xadj[vertlocnbr];

    110:   SCOTCH_dgraphInit(&grafdat, comm);
    111:   SCOTCH_dgraphBuild(&grafdat, 0, vertlocnbr, vertlocnbr, xadj, xadj + 1, veloloctab, NULL, edgelocnbr, edgelocnbr, adjncy, NULL, edloloctab);
    112:   SCOTCH_stratInit(&stradat);
    113:   SCOTCH_stratDgraphMapBuild(&stradat, flagval, procglbnbr, nparts, kbalval);
    114:   SCOTCH_archInit(&archdat);
    115:   if (tpart) { /* target partition weights */
    116:     SCOTCH_archCmpltw(&archdat, nparts, tpart);
    117:   } else {
    118:     SCOTCH_archCmplt(&archdat, nparts);
    119:   }
    120:   SCOTCH_dgraphMapInit(&grafdat, &mappdat, &archdat, part);
    121:   SCOTCH_dgraphMapCompute(&grafdat, &mappdat, &stradat);
    122:   SCOTCH_dgraphMapExit(&grafdat, &mappdat);
    123:   SCOTCH_archExit(&archdat);
    124:   SCOTCH_stratExit(&stradat);
    125:   SCOTCH_dgraphExit(&grafdat);
    126:   return 0;
    127: }

    129: #endif /* PETSC_HAVE_PTSCOTCH */

    131: static const char *const
    132: PTScotchStrategyList[] = {
    133:   "DEFAULT",
    134:   "QUALITY",
    135:   "SPEED",
    136:   "BALANCE",
    137:   "SAFETY",
    138:   "SCALABILITY",
    139:   "RECURSIVE",
    140:   "REMAP"
    141: };

    143: static PetscErrorCode PetscPartitionerDestroy_PTScotch(PetscPartitioner part)
    144: {
    145:   PetscPartitioner_PTScotch *p = (PetscPartitioner_PTScotch *) part->data;

    147:   MPI_Comm_free(&p->pcomm);
    148:   PetscFree(part->data);
    149:   return 0;
    150: }

    152: static PetscErrorCode PetscPartitionerView_PTScotch_ASCII(PetscPartitioner part, PetscViewer viewer)
    153: {
    154:   PetscPartitioner_PTScotch *p = (PetscPartitioner_PTScotch *) part->data;

    156:   PetscViewerASCIIPushTab(viewer);
    157:   PetscViewerASCIIPrintf(viewer,"using partitioning strategy %s\n",PTScotchStrategyList[p->strategy]);
    158:   PetscViewerASCIIPrintf(viewer,"using load imbalance ratio %g\n",(double)p->imbalance);
    159:   PetscViewerASCIIPopTab(viewer);
    160:   return 0;
    161: }

    163: static PetscErrorCode PetscPartitionerView_PTScotch(PetscPartitioner part, PetscViewer viewer)
    164: {
    165:   PetscBool iascii;

    169:   PetscObjectTypeCompare((PetscObject) viewer, PETSCVIEWERASCII, &iascii);
    170:   if (iascii) PetscPartitionerView_PTScotch_ASCII(part, viewer);
    171:   return 0;
    172: }

    174: static PetscErrorCode PetscPartitionerSetFromOptions_PTScotch(PetscOptionItems *PetscOptionsObject, PetscPartitioner part)
    175: {
    176:   PetscPartitioner_PTScotch *p = (PetscPartitioner_PTScotch *) part->data;
    177:   const char *const         *slist = PTScotchStrategyList;
    178:   PetscInt                  nlist = (PetscInt)(sizeof(PTScotchStrategyList)/sizeof(PTScotchStrategyList[0]));
    179:   PetscBool                 flag;

    181:   PetscOptionsHead(PetscOptionsObject, "PetscPartitioner PTScotch Options");
    182:   PetscOptionsEList("-petscpartitioner_ptscotch_strategy","Partitioning strategy","",slist,nlist,slist[p->strategy],&p->strategy,&flag);
    183:   PetscOptionsReal("-petscpartitioner_ptscotch_imbalance","Load imbalance ratio","",p->imbalance,&p->imbalance,&flag);
    184:   PetscOptionsTail();
    185:   return 0;
    186: }

    188: static PetscErrorCode PetscPartitionerPartition_PTScotch(PetscPartitioner part, PetscInt nparts, PetscInt numVertices, PetscInt start[], PetscInt adjacency[], PetscSection vertSection, PetscSection targetSection, PetscSection partSection, IS *partition)
    189: {
    190: #if defined(PETSC_HAVE_PTSCOTCH)
    191:   MPI_Comm     comm;
    192:   PetscInt     nvtxs    = numVertices; /* The number of vertices in full graph */
    193:   PetscInt    *vtxdist;         /* Distribution of vertices across processes */
    194:   PetscInt    *xadj     = start; /* Start of edge list for each vertex */
    195:   PetscInt    *adjncy   = adjacency; /* Edge lists for all vertices */
    196:   PetscInt    *vwgt     = NULL; /* Vertex weights */
    197:   PetscInt    *adjwgt   = NULL; /* Edge weights */
    198:   PetscInt     v, i, *assignment, *points;
    199:   PetscMPIInt  size, rank, p;
    200:   PetscBool    hasempty = PETSC_FALSE;
    201:   PetscInt     *tpwgts  = NULL;

    203:   PetscObjectGetComm((PetscObject)part,&comm);
    204:   MPI_Comm_size(comm, &size);
    205:   MPI_Comm_rank(comm, &rank);
    206:   PetscMalloc2(size+1,&vtxdist,PetscMax(nvtxs,1),&assignment);
    207:   /* Calculate vertex distribution */
    208:   vtxdist[0] = 0;
    209:   MPI_Allgather(&nvtxs, 1, MPIU_INT, &vtxdist[1], 1, MPIU_INT, comm);
    210:   for (p = 2; p <= size; ++p) {
    211:     hasempty = (PetscBool)(hasempty || !vtxdist[p-1] || !vtxdist[p]);
    212:     vtxdist[p] += vtxdist[p-1];
    213:   }
    214:   /* null graph */
    215:   if (vtxdist[size] == 0) {
    216:     PetscFree2(vtxdist, assignment);
    217:     ISCreateGeneral(comm, 0, NULL, PETSC_OWN_POINTER, partition);
    218:     return 0;
    219:   }

    221:   /* Calculate vertex weights */
    222:   if (vertSection) {
    223:     PetscMalloc1(nvtxs,&vwgt);
    224:     for (v = 0; v < nvtxs; ++v) PetscSectionGetDof(vertSection, v, &vwgt[v]);
    225:   }

    227:   /* Calculate partition weights */
    228:   if (targetSection) {
    229:     PetscInt sumw;

    231:     PetscCalloc1(nparts,&tpwgts);
    232:     for (p = 0, sumw = 0; p < nparts; ++p) {
    233:       PetscSectionGetDof(targetSection,p,&tpwgts[p]);
    234:       sumw += tpwgts[p];
    235:     }
    236:     if (!sumw) PetscFree(tpwgts);
    237:   }

    239:   {
    240:     PetscPartitioner_PTScotch *pts = (PetscPartitioner_PTScotch *) part->data;
    241:     int                       strat = PTScotch_Strategy(pts->strategy);
    242:     double                    imbal = (double)pts->imbalance;

    244:     for (p = 0; !vtxdist[p+1] && p < size; ++p);
    245:     if (vtxdist[p+1] == vtxdist[size]) {
    246:       if (rank == p) PTScotch_PartGraph_Seq(strat, imbal, nvtxs, xadj, adjncy, vwgt, adjwgt, nparts, tpwgts, assignment);
    247:     } else {
    248:       MPI_Comm pcomm = pts->pcomm;

    250:       if (hasempty) {
    251:         PetscInt cnt;

    253:         MPI_Comm_split(pts->pcomm,!!nvtxs,rank,&pcomm);
    254:         for (p=0,cnt=0;p<size;p++) {
    255:           if (vtxdist[p+1] != vtxdist[p]) {
    256:             vtxdist[cnt+1] = vtxdist[p+1];
    257:             cnt++;
    258:           }
    259:         }
    260:       };
    261:       if (nvtxs) PTScotch_PartGraph_MPI(strat, imbal, vtxdist, xadj, adjncy, vwgt, adjwgt, nparts, tpwgts, assignment, pcomm);
    262:       if (hasempty) MPI_Comm_free(&pcomm);
    263:     }
    264:   }
    265:   PetscFree(vwgt);
    266:   PetscFree(tpwgts);

    268:   /* Convert to PetscSection+IS */
    269:   for (v = 0; v < nvtxs; ++v) PetscSectionAddDof(partSection, assignment[v], 1);
    270:   PetscMalloc1(nvtxs, &points);
    271:   for (p = 0, i = 0; p < nparts; ++p) {
    272:     for (v = 0; v < nvtxs; ++v) {
    273:       if (assignment[v] == p) points[i++] = v;
    274:     }
    275:   }
    277:   ISCreateGeneral(comm, nvtxs, points, PETSC_OWN_POINTER, partition);

    279:   PetscFree2(vtxdist,assignment);
    280:   return 0;
    281: #else
    282:   SETERRQ(PetscObjectComm((PetscObject) part), PETSC_ERR_SUP, "Mesh partitioning needs external package support.\nPlease reconfigure with --download-ptscotch.");
    283: #endif
    284: }

    286: static PetscErrorCode PetscPartitionerInitialize_PTScotch(PetscPartitioner part)
    287: {
    288:   part->noGraph             = PETSC_FALSE;
    289:   part->ops->view           = PetscPartitionerView_PTScotch;
    290:   part->ops->destroy        = PetscPartitionerDestroy_PTScotch;
    291:   part->ops->partition      = PetscPartitionerPartition_PTScotch;
    292:   part->ops->setfromoptions = PetscPartitionerSetFromOptions_PTScotch;
    293:   return 0;
    294: }

    296: /*MC
    297:   PETSCPARTITIONERPTSCOTCH = "ptscotch" - A PetscPartitioner object using the PT-Scotch library

    299:   Level: intermediate

    301:   Options Database Keys:
    302: +  -petscpartitioner_ptscotch_strategy <string> - PT-Scotch strategy. Choose one of default quality speed balance safety scalability recursive remap
    303: -  -petscpartitioner_ptscotch_imbalance <val> - Load imbalance ratio

    305:   Notes: when the graph is on a single process, this partitioner actually uses Scotch and not PT-Scotch

    307: .seealso: PetscPartitionerType, PetscPartitionerCreate(), PetscPartitionerSetType()
    308: M*/

    310: PETSC_EXTERN PetscErrorCode PetscPartitionerCreate_PTScotch(PetscPartitioner part)
    311: {
    312:   PetscPartitioner_PTScotch *p;

    315:   PetscNewLog(part, &p);
    316:   part->data = p;

    318:   MPI_Comm_dup(PetscObjectComm((PetscObject)part),&p->pcomm);
    319:   p->strategy  = 0;
    320:   p->imbalance = 0.01;

    322:   PetscPartitionerInitialize_PTScotch(part);
    323:   PetscCitationsRegister(PTScotchPartitionerCitation, &PTScotchPartitionerCite);
    324:   return 0;
    325: }