Actual source code: hem.c
petsc-3.10.5 2019-03-28
Report Typos and Errors

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

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

     16:   /* alocate pool, partially */
     17:   PetscNew(&ail);
     18:   *a_out               = ail;
     19:   ail->pool_list.next  = NULL;
     20:   ail->pool_list.array = NULL;
     21:   ail->chk_sz          = 0;
     22:   /* allocate array */
     23:   ail->size = a_size;
     24:   PetscCalloc1(a_size, &ail->array);
     25:   ail->extra_nodes = NULL;
     26:   ail->mat         = NULL;
     27:   return(0);
     28: }

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

     38:   n = n->next;
     39:   while (n) {
     40:     PetscCDArrNd *lstn = n;
     41:     n    = n->next;
     42:     PetscFree(lstn);
     43:   }
     44:   if (ail->pool_list.array) {
     45:     PetscFree(ail->pool_list.array);
     46:   }
     47:   PetscFree(ail->array);
     48:   /* delete this (+agg+pool array) */
     49:   PetscFree(ail);
     50:   return(0);
     51: }

     53: /* PetscCDSetChuckSize
     54:  */
     55: PetscErrorCode PetscCDSetChuckSize(PetscCoarsenData *ail, PetscInt a_sz)
     56: {
     58:   ail->chk_sz = a_sz;
     59:   return(0);
     60: }

     62: /*  PetscCDGetNewNode
     63:  */
     64: PetscErrorCode PetscCDGetNewNode(PetscCoarsenData *ail, PetscCDIntNd **a_out, PetscInt a_id)
     65: {

     69:   *a_out = NULL;                /* squelch -Wmaybe-uninitialized */
     70:   if (ail->extra_nodes) {
     71:     PetscCDIntNd *node = ail->extra_nodes;
     72:     ail->extra_nodes = node->next;
     73:     node->gid        = a_id;
     74:     node->next       = NULL;
     75:     *a_out           = node;
     76:   } else {
     77:     if (!ail->pool_list.array) {
     78:       if (!ail->chk_sz) ail->chk_sz = 10; /* use a chuck size of ail->size? */
     79:       PetscMalloc1(ail->chk_sz, &ail->pool_list.array);
     80:       ail->new_node       = ail->pool_list.array;
     81:       ail->new_left       = ail->chk_sz;
     82:       ail->new_node->next = NULL;
     83:     } else if (!ail->new_left) {
     84:       PetscCDArrNd *node;
     85:       PetscMalloc(ail->chk_sz*sizeof(PetscCDIntNd) + sizeof(PetscCDArrNd), &node);
     86:       node->array         = (PetscCDIntNd*)(node + 1);
     87:       node->next          = ail->pool_list.next;
     88:       ail->pool_list.next = node;
     89:       ail->new_left       = ail->chk_sz;
     90:       ail->new_node       = node->array;
     91:     }
     92:     ail->new_node->gid  = a_id;
     93:     ail->new_node->next = NULL;
     94:     *a_out              = ail->new_node++; ail->new_left--;
     95:   }
     96:   return(0);
     97: }

     99: /* PetscCDIntNdSetID
    100:  */
    101: PetscErrorCode PetscCDIntNdSetID(PetscCDIntNd *a_this, PetscInt a_id)
    102: {
    104:   a_this->gid = a_id;
    105:   return(0);
    106: }

    108: /* PetscCDIntNdGetID
    109:  */
    110: PetscErrorCode PetscCDIntNdGetID(const PetscCDIntNd *a_this, PetscInt *a_gid)
    111: {
    113:   *a_gid = a_this->gid;
    114:   return(0);
    115: }

    117: /* PetscCDGetHeadPos
    118:  */
    119: PetscErrorCode PetscCDGetHeadPos(const PetscCoarsenData *ail, PetscInt a_idx, PetscCDIntNd **pos)
    120: {
    122:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"a_idx >= ail->size: a_idx=%D.",a_idx);
    123:   *pos = ail->array[a_idx];
    124:   return(0);
    125: }

    127: /* PetscCDGetNextPos
    128:  */
    129: PetscErrorCode PetscCDGetNextPos(const PetscCoarsenData *ail, PetscInt l_idx, PetscCDIntNd **pos)
    130: {
    132:   if (!(*pos)) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"NULL input position.");
    133:   *pos = (*pos)->next;
    134:   return(0);
    135: }

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

    145:   PetscCDGetNewNode(ail, &n, a_id);
    146:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    147:   if (!(n2=ail->array[a_idx])) ail->array[a_idx] = n;
    148:   else {
    149:     do {
    150:       if (!n2->next) {
    151:         n2->next = n;
    152:         if (n->next) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"n should not have a next");
    153:         break;
    154:       }
    155:       n2 = n2->next;
    156:     } while (n2);
    157:     if (!n2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"n2 should be non-null");
    158:   }
    159:   return(0);
    160: }

    162: /* PetscCDAppendNode
    163:  */
    164: PetscErrorCode PetscCDAppendNode(PetscCoarsenData *ail, PetscInt a_idx,  PetscCDIntNd *a_n)
    165: {
    166:   PetscCDIntNd *n2;

    169:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    170:   if (!(n2=ail->array[a_idx])) ail->array[a_idx] = a_n;
    171:   else {
    172:     do {
    173:       if (!n2->next) {
    174:         n2->next  = a_n;
    175:         a_n->next = NULL;
    176:         break;
    177:       }
    178:       n2 = n2->next;
    179:     } while (n2);
    180:     if (!n2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"n2 should be non-null");
    181:   }
    182:   return(0);
    183: }

    185: /* PetscCDRemoveNextNode: a_last->next, this exposes single linked list structure to API
    186:  */
    187: PetscErrorCode PetscCDRemoveNextNode(PetscCoarsenData *ail, PetscInt a_idx,  PetscCDIntNd *a_last)
    188: {
    189:   PetscCDIntNd *del;

    192:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    193:   if (!a_last->next) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"a_last should have a next");
    194:   del          = a_last->next;
    195:   a_last->next = del->next;
    196:   /* del->next = NULL; -- this still used in a iterator so keep it intact -- need to fix this with a double linked list */
    197:   /* could reuse n2 but PetscCDAppendNode sometimes uses it */
    198:   return(0);
    199: }

    201: /* PetscCDPrint
    202:  */
    203: PetscErrorCode PetscCDPrint(const PetscCoarsenData *ail, MPI_Comm comm)
    204: {
    206:   PetscCDIntNd   *n;
    207:   PetscInt       ii,kk;
    208:   PetscMPIInt    rank;

    211:   MPI_Comm_rank(comm, &rank);
    212:   for (ii=0; ii<ail->size; ii++) {
    213:     kk = 0;
    214:     n  = ail->array[ii];
    215:     if (n) {PetscPrintf(comm,"[%d]%s list %d:\n",rank,PETSC_FUNCTION_NAME,ii);}
    216:     while (n) {
    217:       PetscPrintf(comm,"\t[%d] %D) id %D\n",rank,++kk,n->gid);
    218:       n = n->next;
    219:     }
    220:   }
    221:   return(0);
    222: }

    224: /* PetscCDAppendRemove
    225:  */
    226: PetscErrorCode PetscCDAppendRemove(PetscCoarsenData *ail, PetscInt a_destidx, PetscInt a_srcidx)
    227: {
    228:   PetscCDIntNd *n;

    231:   if (a_srcidx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_srcidx);
    232:   if (a_destidx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_destidx);
    233:   if (a_destidx==a_srcidx) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"a_destidx==a_srcidx %D.",a_destidx);
    234:   n = ail->array[a_destidx];
    235:   if (!n) ail->array[a_destidx] = ail->array[a_srcidx];
    236:   else {
    237:     do {
    238:       if (!n->next) {
    239:         n->next = ail->array[a_srcidx];
    240:         break;
    241:       }
    242:       n = n->next;
    243:     } while (1);
    244:   }
    245:   ail->array[a_srcidx] = NULL;
    246:   return(0);
    247: }

    249: /* PetscCDRemoveAll
    250:  */
    251: PetscErrorCode PetscCDRemoveAll(PetscCoarsenData *ail, PetscInt a_idx)
    252: {
    253:   PetscCDIntNd *rem,*n1;

    256:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    257:   rem               = ail->array[a_idx];
    258:   ail->array[a_idx] = NULL;
    259:   if (!(n1=ail->extra_nodes)) ail->extra_nodes = rem;
    260:   else {
    261:     while (n1->next) n1 = n1->next;
    262:     n1->next = rem;
    263:   }
    264:   return(0);
    265: }

    267: /* PetscCDSizeAt
    268:  */
    269: PetscErrorCode PetscCDSizeAt(const PetscCoarsenData *ail, PetscInt a_idx, PetscInt *a_sz)
    270: {
    271:   PetscCDIntNd *n1;
    272:   PetscInt     sz = 0;

    275:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    276:   n1 = ail->array[a_idx];
    277:   while (n1) {
    278:     n1 = n1->next;
    279:     sz++;
    280:   }
    281:   *a_sz = sz;
    282:   return(0);
    283: }

    285: /* PetscCDEmptyAt
    286:  */
    287: PetscErrorCode PetscCDEmptyAt(const PetscCoarsenData *ail, PetscInt a_idx, PetscBool *a_e)
    288: {
    290:   if (a_idx>=ail->size) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Index %D out of range.",a_idx);
    291:   *a_e = (PetscBool)(ail->array[a_idx]==NULL);
    292:   return(0);
    293: }

    295: /* PetscCDGetMIS
    296:  */
    297: PetscErrorCode PetscCDGetMIS(PetscCoarsenData *ail, IS *a_mis)
    298: {
    300:   PetscCDIntNd   *n;
    301:   PetscInt       ii,kk;
    302:   PetscInt       *permute;

    305:   for (ii=kk=0; ii<ail->size; ii++) {
    306:     n = ail->array[ii];
    307:     if (n) kk++;
    308:   }
    309:   PetscMalloc1(kk, &permute);
    310:   for (ii=kk=0; ii<ail->size; ii++) {
    311:     n = ail->array[ii];
    312:     if (n) permute[kk++] = ii;
    313:   }
    314:   ISCreateGeneral(PETSC_COMM_SELF, kk, permute, PETSC_OWN_POINTER, a_mis);
    315:   return(0);
    316: }

    318: /* PetscCDGetMat
    319:  */
    320: PetscErrorCode PetscCDGetMat(const PetscCoarsenData *ail, Mat *a_mat)
    321: {
    323:   *a_mat = ail->mat;
    324:   return(0);
    325: }

    327: /* PetscCDSetMat
    328:  */
    329: PetscErrorCode PetscCDSetMat(PetscCoarsenData *ail, Mat a_mat)
    330: {
    332:   ail->mat = a_mat;
    333:   return(0);
    334: }

    336: /* PetscCDGetASMBlocks
    337:  */
    338: PetscErrorCode PetscCDGetASMBlocks(const PetscCoarsenData *ail, const PetscInt a_bs, Mat mat, PetscInt *a_sz, IS **a_local_is)
    339: {
    341:   PetscCDIntNd   *n;
    342:   PetscInt       lsz,ii,kk,*idxs,jj,s,e,gid;
    343:   IS             *is_loc,is_bcs;

    346:   for (ii=kk=0; ii<ail->size; ii++) {
    347:     if (ail->array[ii]) kk++;
    348:   }
    349:   /* count BCs */
    350:   MatGetOwnershipRange(mat, &s, &e);
    351:   for (gid=s,lsz=0; gid<e; gid++) {
    352:     MatGetRow(mat,gid,&jj,0,0);
    353:     if (jj<2) lsz++;
    354:     MatRestoreRow(mat,gid,&jj,0,0);
    355:   }
    356:   if (lsz) {
    357:     PetscMalloc1(a_bs*lsz, &idxs);
    358:     for (gid=s,lsz=0; gid<e; gid++) {
    359:       MatGetRow(mat,gid,&jj,0,0);
    360:       if (jj<2) {
    361:         for (jj=0; jj<a_bs; lsz++,jj++) idxs[lsz] = a_bs*gid + jj;
    362:       }
    363:       MatRestoreRow(mat,gid,&jj,0,0);
    364:     }
    365:     ISCreateGeneral(PETSC_COMM_SELF, lsz, idxs, PETSC_OWN_POINTER, &is_bcs);
    366:     *a_sz = kk + 1; /* out */
    367:   } else {
    368:     is_bcs=0;
    369:     *a_sz = kk; /* out */
    370:   }
    371:   PetscMalloc1(*a_sz, &is_loc);

    373:   for (ii=kk=0; ii<ail->size; ii++) {
    374:     for (lsz=0, n=ail->array[ii]; n; lsz++, n=n->next) /* void */;
    375:     if (lsz) {
    376:       PetscMalloc1(a_bs*lsz, &idxs);
    377:       for (lsz = 0, n=ail->array[ii]; n; n = n->next) {
    378:         PetscCDIntNdGetID(n, &gid);
    379:         for (jj=0; jj<a_bs; lsz++,jj++) idxs[lsz] = a_bs*gid + jj;
    380:       }
    381:       ISCreateGeneral(PETSC_COMM_SELF, lsz, idxs, PETSC_OWN_POINTER, &is_loc[kk++]);
    382:     }
    383:   }
    384:   if (is_bcs) {
    385:     is_loc[kk++] = is_bcs;
    386:   }
    387:   if (*a_sz != kk) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"*a_sz %D != kk %D",*a_sz,kk);
    388:   *a_local_is = is_loc; /* out */

    390:   return(0);
    391: }

    393: /* ********************************************************************** */
    394: /* edge for priority queue */
    395: typedef struct edge_tag {
    396:   PetscReal weight;
    397:   PetscInt  lid0,gid1,cpid1;
    398: } Edge;

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

    406: /* -------------------------------------------------------------------------- */
    407: /*
    408:    heavyEdgeMatchAgg - parallel heavy edge matching (HEM). MatAIJ specific!!!

    410:    Input Parameter:
    411:    . perm - permutation
    412:    . a_Gmat - glabal matrix of graph (data not defined)

    414:    Output Parameter:
    415:    . a_locals_llist - array of list of local nodes rooted at local node
    416: */
    417: static PetscErrorCode heavyEdgeMatchAgg(IS perm,Mat a_Gmat,PetscCoarsenData **a_locals_llist)
    418: {
    419:   PetscErrorCode   ierr;
    420:   PetscBool        isMPI;
    421:   MPI_Comm         comm;
    422:   PetscInt         sub_it,kk,n,ix,*idx,*ii,iter,Iend,my0;
    423:   PetscMPIInt      rank,size;
    424:   const PetscInt   nloc = a_Gmat->rmap->n,n_iter=6; /* need to figure out how to stop this */
    425:   PetscInt         *lid_cprowID,*lid_gid;
    426:   PetscBool        *lid_matched;
    427:   Mat_SeqAIJ       *matA, *matB=0;
    428:   Mat_MPIAIJ       *mpimat     =0;
    429:   PetscScalar      one         =1.;
    430:   PetscCoarsenData *agg_llists = NULL,*deleted_list = NULL;
    431:   Mat              cMat,tMat,P;
    432:   MatScalar        *ap;
    433:   PetscMPIInt      tag1,tag2;

    436:   PetscObjectGetComm((PetscObject)a_Gmat,&comm);
    437:   MPI_Comm_rank(comm, &rank);
    438:   MPI_Comm_size(comm, &size);
    439:   MatGetOwnershipRange(a_Gmat, &my0, &Iend);
    440:   PetscCommGetNewTag(comm, &tag1);
    441:   PetscCommGetNewTag(comm, &tag2);

    443:   PetscMalloc1(nloc, &lid_gid); /* explicit array needed */
    444:   PetscMalloc1(nloc, &lid_cprowID);
    445:   PetscMalloc1(nloc, &lid_matched);

    447:   PetscCDCreate(nloc, &agg_llists);
    448:   /* PetscCDSetChuckSize(agg_llists, nloc+1); */
    449:   *a_locals_llist = agg_llists;
    450:   PetscCDCreate(size, &deleted_list);
    451:   PetscCDSetChuckSize(deleted_list, 100);
    452:   /* setup 'lid_gid' for scatters and add self to all lists */
    453:   for (kk=0; kk<nloc; kk++) {
    454:     lid_gid[kk] = kk + my0;
    455:     PetscCDAppendID(agg_llists, kk, my0+kk);
    456:   }

    458:   /* make a copy of the graph, this gets destroyed in iterates */
    459:   MatDuplicate(a_Gmat,MAT_COPY_VALUES,&cMat);
    460:   PetscObjectTypeCompare((PetscObject)a_Gmat, MATMPIAIJ, &isMPI);
    461:   iter = 0;
    462:   while (iter++ < n_iter) {
    463:     PetscScalar    *cpcol_gid,*cpcol_max_ew,*cpcol_max_pe,*lid_max_ew;
    464:     PetscBool      *cpcol_matched;
    465:     PetscMPIInt    *cpcol_pe,proc;
    466:     Vec            locMaxEdge,locMaxPE,ghostMaxEdge,ghostMaxPE;
    467:     PetscInt       nEdges,n_nz_row,jj;
    468:     Edge           *Edges;
    469:     PetscInt       gid;
    470:     const PetscInt *perm_ix, n_sub_its = 120;

    472:     /* get submatrices of cMat */
    473:     if (isMPI) {
    474:       mpimat = (Mat_MPIAIJ*)cMat->data;
    475:       matA   = (Mat_SeqAIJ*)mpimat->A->data;
    476:       matB   = (Mat_SeqAIJ*)mpimat->B->data;
    477:       if (!matB->compressedrow.use) {
    478:         /* force construction of compressed row data structure since code below requires it */
    479:         MatCheckCompressedRow(mpimat->B,matB->nonzerorowcnt,&matB->compressedrow,matB->i,mpimat->B->rmap->n,-1.0);
    480:       }
    481:     } else {
    482:       matA = (Mat_SeqAIJ*)cMat->data;
    483:     }

    485:     /* set max edge on nodes */
    486:     MatCreateVecs(cMat, &locMaxEdge, 0);
    487:     MatCreateVecs(cMat, &locMaxPE, 0);

    489:     /* get 'cpcol_pe' & 'cpcol_gid' & init. 'cpcol_matched' using 'mpimat->lvec' */
    490:     if (mpimat) {
    491:       Vec         vec;
    492:       PetscScalar vval;

    494:       MatCreateVecs(cMat, &vec, 0);
    495:       /* cpcol_pe */
    496:       vval = (PetscScalar)(rank);
    497:       for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    498:         VecSetValues(vec, 1, &gid, &vval, INSERT_VALUES); /* set with GID */
    499:       }
    500:       VecAssemblyBegin(vec);
    501:       VecAssemblyEnd(vec);
    502:       VecScatterBegin(mpimat->Mvctx,vec,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    503:       VecScatterEnd(mpimat->Mvctx,vec,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    504:       VecGetArray(mpimat->lvec, &cpcol_gid); /* get proc ID in 'cpcol_gid' */
    505:       VecGetLocalSize(mpimat->lvec, &n);
    506:       PetscMalloc1(n, &cpcol_pe);
    507:       for (kk=0; kk<n; kk++) cpcol_pe[kk] = (PetscMPIInt)PetscRealPart(cpcol_gid[kk]);
    508:       VecRestoreArray(mpimat->lvec, &cpcol_gid);

    510:       /* cpcol_gid */
    511:       for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    512:         vval = (PetscScalar)(gid);
    513:         VecSetValues(vec, 1, &gid, &vval, INSERT_VALUES); /* set with GID */
    514:       }
    515:       VecAssemblyBegin(vec);
    516:       VecAssemblyEnd(vec);
    517:       VecScatterBegin(mpimat->Mvctx,vec,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    518:       VecScatterEnd(mpimat->Mvctx,vec,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    519:       VecDestroy(&vec);
    520:       VecGetArray(mpimat->lvec, &cpcol_gid); /* get proc ID in 'cpcol_gid' */

    522:       /* cpcol_matched */
    523:       VecGetLocalSize(mpimat->lvec, &n);
    524:       PetscMalloc1(n, &cpcol_matched);
    525:       for (kk=0; kk<n; kk++) cpcol_matched[kk] = PETSC_FALSE;
    526:     }

    528:     /* need an inverse map - locals */
    529:     for (kk=0; kk<nloc; kk++) lid_cprowID[kk] = -1;
    530:     /* set index into compressed row 'lid_cprowID' */
    531:     if (matB) {
    532:       for (ix=0; ix<matB->compressedrow.nrows; ix++) {
    533:         lid_cprowID[matB->compressedrow.rindex[ix]] = ix;
    534:       }
    535:     }

    537:     /* compute 'locMaxEdge' & 'locMaxPE', and create list of edges, count edges' */
    538:     for (nEdges=0,kk=0,gid=my0; kk<nloc; kk++,gid++) {
    539:       PetscReal   max_e = 0., tt;
    540:       PetscScalar vval;
    541:       PetscInt    lid   = kk;
    542:       PetscMPIInt max_pe=rank,pe;

    544:       ii = matA->i; n = ii[lid+1] - ii[lid]; idx = matA->j + ii[lid];
    545:       ap = matA->a + ii[lid];
    546:       for (jj=0; jj<n; jj++) {
    547:         PetscInt lidj = idx[jj];
    548:         if (lidj != lid && PetscRealPart(ap[jj]) > max_e) max_e = PetscRealPart(ap[jj]);
    549:         if (lidj > lid) nEdges++;
    550:       }
    551:       if ((ix=lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
    552:         ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    553:         ap  = matB->a + ii[ix];
    554:         idx = matB->j + ii[ix];
    555:         for (jj=0; jj<n; jj++) {
    556:           if ((tt=PetscRealPart(ap[jj])) > max_e) max_e = tt;
    557:           nEdges++;
    558:           if ((pe=cpcol_pe[idx[jj]]) > max_pe) max_pe = pe;
    559:         }
    560:       }
    561:       vval = max_e;
    562:       VecSetValues(locMaxEdge, 1, &gid, &vval, INSERT_VALUES);

    564:       vval = (PetscScalar)max_pe;
    565:       VecSetValues(locMaxPE, 1, &gid, &vval, INSERT_VALUES);
    566:     }
    567:     VecAssemblyBegin(locMaxEdge);
    568:     VecAssemblyEnd(locMaxEdge);
    569:     VecAssemblyBegin(locMaxPE);
    570:     VecAssemblyEnd(locMaxPE);

    572:     /* get 'cpcol_max_ew' & 'cpcol_max_pe' */
    573:     if (mpimat) {
    574:       VecDuplicate(mpimat->lvec, &ghostMaxEdge);
    575:       VecScatterBegin(mpimat->Mvctx,locMaxEdge,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    576:       VecScatterEnd(mpimat->Mvctx,locMaxEdge,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    577:       VecGetArray(ghostMaxEdge, &cpcol_max_ew);

    579:       VecDuplicate(mpimat->lvec, &ghostMaxPE);
    580:       VecScatterBegin(mpimat->Mvctx,locMaxPE,ghostMaxPE,INSERT_VALUES,SCATTER_FORWARD);
    581:       VecScatterEnd(mpimat->Mvctx,locMaxPE,ghostMaxPE,INSERT_VALUES,SCATTER_FORWARD);
    582:       VecGetArray(ghostMaxPE, &cpcol_max_pe);
    583:     }

    585:     /* setup sorted list of edges */
    586:     PetscMalloc1(nEdges, &Edges);
    587:     ISGetIndices(perm, &perm_ix);
    588:     for (nEdges=n_nz_row=kk=0; kk<nloc; kk++) {
    589:       PetscInt nn, lid = perm_ix[kk];
    590:       ii = matA->i; nn = n = ii[lid+1] - ii[lid]; idx = matA->j + ii[lid];
    591:       ap = matA->a + ii[lid];
    592:       for (jj=0; jj<n; jj++) {
    593:         PetscInt lidj = idx[jj];
    594:         if (lidj > lid) {
    595:           Edges[nEdges].lid0   = lid;
    596:           Edges[nEdges].gid1   = lidj + my0;
    597:           Edges[nEdges].cpid1  = -1;
    598:           Edges[nEdges].weight = PetscRealPart(ap[jj]);
    599:           nEdges++;
    600:         }
    601:       }
    602:       if ((ix=lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
    603:         ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    604:         ap  = matB->a + ii[ix];
    605:         idx = matB->j + ii[ix];
    606:         nn += n;
    607:         for (jj=0; jj<n; jj++) {
    608:           Edges[nEdges].lid0   = lid;
    609:           Edges[nEdges].gid1   = (PetscInt)PetscRealPart(cpcol_gid[idx[jj]]);
    610:           Edges[nEdges].cpid1  = idx[jj];
    611:           Edges[nEdges].weight = PetscRealPart(ap[jj]);
    612:           nEdges++;
    613:         }
    614:       }
    615:       if (nn > 1) n_nz_row++;
    616:       else if (iter == 1) {
    617:         /* should select this because it is technically in the MIS but lets not */
    618:         PetscCDRemoveAll(agg_llists, lid);
    619:       }
    620:     }
    621:     ISRestoreIndices(perm,&perm_ix);

    623:     qsort(Edges, nEdges, sizeof(Edge), gamg_hem_compare);

    625:     /* projection matrix */
    626:     MatCreateAIJ(comm, nloc, nloc, PETSC_DETERMINE, PETSC_DETERMINE, 1, 0, 1, 0, &P);

    628:     /* clear matched flags */
    629:     for (kk=0; kk<nloc; kk++) lid_matched[kk] = PETSC_FALSE;
    630:     /* process - communicate - process */
    631:     for (sub_it=0; sub_it<n_sub_its; sub_it++) {
    632:       PetscInt nactive_edges;

    634:       VecGetArray(locMaxEdge, &lid_max_ew);
    635:       for (kk=nactive_edges=0; kk<nEdges; kk++) {
    636:         /* HEM */
    637:         const Edge     *e   = &Edges[kk];
    638:         const PetscInt lid0 =e->lid0,gid1=e->gid1,cpid1=e->cpid1,gid0=lid0+my0,lid1=gid1-my0;
    639:         PetscBool      isOK = PETSC_TRUE;

    641:         /* skip if either (local) vertex is done already */
    642:         if (lid_matched[lid0] || (gid1>=my0 && gid1<Iend && lid_matched[gid1-my0])) continue;

    644:         /* skip if ghost vertex is done */
    645:         if (cpid1 != -1 && cpcol_matched[cpid1]) continue;

    647:         nactive_edges++;
    648:         /* skip if I have a bigger edge someplace (lid_max_ew gets updated) */
    649:         if (PetscRealPart(lid_max_ew[lid0]) > e->weight + PETSC_SMALL) continue;

    651:         if (cpid1 == -1) {
    652:           if (PetscRealPart(lid_max_ew[lid1]) > e->weight + PETSC_SMALL) continue;
    653:         } else {
    654:           /* see if edge might get matched on other proc */
    655:           PetscReal g_max_e = PetscRealPart(cpcol_max_ew[cpid1]);
    656:           if (g_max_e > e->weight + PETSC_SMALL) continue;
    657:           else if (e->weight > g_max_e - PETSC_SMALL && (PetscMPIInt)PetscRealPart(cpcol_max_pe[cpid1]) > rank) {
    658:             /* check for max_e == to this edge and larger processor that will deal with this */
    659:             continue;
    660:           }
    661:         }

    663:         /* check ghost for v0 */
    664:         if (isOK) {
    665:           PetscReal max_e,ew;
    666:           if ((ix=lid_cprowID[lid0]) != -1) { /* if I have any ghost neighbors */
    667:             ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    668:             ap  = matB->a + ii[ix];
    669:             idx = matB->j + ii[ix];
    670:             for (jj=0; jj<n && isOK; jj++) {
    671:               PetscInt lidj = idx[jj];
    672:               if (cpcol_matched[lidj]) continue;
    673:               ew = PetscRealPart(ap[jj]); max_e = PetscRealPart(cpcol_max_ew[lidj]);
    674:               /* check for max_e == to this edge and larger processor that will deal with this */
    675:               if (ew > max_e - PETSC_SMALL && ew > PetscRealPart(lid_max_ew[lid0]) - PETSC_SMALL && (PetscMPIInt)PetscRealPart(cpcol_max_pe[lidj]) > rank) {
    676:                 isOK = PETSC_FALSE;
    677:               }
    678:             }
    679:           }

    681:           /* for v1 */
    682:           if (cpid1 == -1 && isOK) {
    683:             if ((ix=lid_cprowID[lid1]) != -1) { /* if I have any ghost neighbors */
    684:               ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    685:               ap  = matB->a + ii[ix];
    686:               idx = matB->j + ii[ix];
    687:               for (jj=0; jj<n && isOK; jj++) {
    688:                 PetscInt lidj = idx[jj];
    689:                 if (cpcol_matched[lidj]) continue;
    690:                 ew = PetscRealPart(ap[jj]); max_e = PetscRealPart(cpcol_max_ew[lidj]);
    691:                 /* check for max_e == to this edge and larger processor that will deal with this */
    692:                 if (ew > max_e - PETSC_SMALL && ew > PetscRealPart(lid_max_ew[lid1]) - PETSC_SMALL && (PetscMPIInt)PetscRealPart(cpcol_max_pe[lidj]) > rank) {
    693:                   isOK = PETSC_FALSE;
    694:                 }
    695:               }
    696:             }
    697:           }
    698:         }

    700:         /* do it */
    701:         if (isOK) {
    702:           if (cpid1 == -1) {
    703:             lid_matched[lid1] = PETSC_TRUE;  /* keep track of what we've done this round */
    704:             PetscCDAppendRemove(agg_llists, lid0, lid1);
    705:           } else if (sub_it != n_sub_its-1) {
    706:             /* add gid1 to list of ghost deleted by me -- I need their children */
    707:             proc = cpcol_pe[cpid1];

    709:             cpcol_matched[cpid1] = PETSC_TRUE; /* messing with VecGetArray array -- needed??? */

    711:             PetscCDAppendID(deleted_list, proc, cpid1); /* cache to send messages */
    712:             PetscCDAppendID(deleted_list, proc, lid0);
    713:           } else continue;

    715:           lid_matched[lid0] = PETSC_TRUE; /* keep track of what we've done this round */
    716:           /* set projection */
    717:           MatSetValues(P,1,&gid0,1,&gid0,&one,INSERT_VALUES);
    718:           MatSetValues(P,1,&gid1,1,&gid0,&one,INSERT_VALUES);
    719:         } /* matched */
    720:       } /* edge loop */

    722:       /* deal with deleted ghost on first pass */
    723:       if (size>1 && sub_it != n_sub_its-1) {
    724: #define REQ_BF_SIZE 100
    725:         PetscCDIntNd *pos;
    726:         PetscBool    ise = PETSC_FALSE;
    727:         PetscInt     nSend1, **sbuffs1,nSend2;
    728:         MPI_Request  *sreqs2[REQ_BF_SIZE],*rreqs2[REQ_BF_SIZE];
    729:         MPI_Status   status;

    731:         /* send request */
    732:         for (proc=0,nSend1=0; proc<size; proc++) {
    733:           PetscCDEmptyAt(deleted_list,proc,&ise);
    734:           if (!ise) nSend1++;
    735:         }
    736:         PetscMalloc1(nSend1, &sbuffs1);
    737:         for (proc=0,nSend1=0; proc<size; proc++) {
    738:           /* count ghosts */
    739:           PetscCDSizeAt(deleted_list,proc,&n);
    740:           if (n>0) {
    741: #define CHUNCK_SIZE 100
    742:             PetscInt    *sbuff,*pt;
    743:             MPI_Request *request;
    744:             n   /= 2;
    745:             PetscMalloc1(2 + 2*n + n*CHUNCK_SIZE + 2, &sbuff);
    746:             /* save requests */
    747:             sbuffs1[nSend1] = sbuff;
    748:             request         = (MPI_Request*)sbuff;
    749:             sbuff           = pt = (PetscInt*)(request+1);
    750:             *pt++           = n; *pt++ = rank;

    752:             PetscCDGetHeadPos(deleted_list,proc,&pos);
    753:             while (pos) {
    754:               PetscInt lid0, cpid, gid;
    755:               PetscCDIntNdGetID(pos, &cpid);
    756:               gid   = (PetscInt)PetscRealPart(cpcol_gid[cpid]);
    757:               PetscCDGetNextPos(deleted_list,proc,&pos);
    758:               PetscCDIntNdGetID(pos, &lid0);
    759:               PetscCDGetNextPos(deleted_list,proc,&pos);
    760:               *pt++ = gid; *pt++ = lid0;
    761:             }
    762:             /* send request tag1 [n, proc, n*[gid1,lid0] ] */
    763:             MPI_Isend(sbuff, 2*n+2, MPIU_INT, proc, tag1, comm, request);
    764:             /* post recieve */
    765:             request        = (MPI_Request*)pt;
    766:             rreqs2[nSend1] = request; /* cache recv request */
    767:             pt             = (PetscInt*)(request+1);
    768:             MPI_Irecv(pt, n*CHUNCK_SIZE, MPIU_INT, proc, tag2, comm, request);
    769:             /* clear list */
    770:             PetscCDRemoveAll(deleted_list, proc);
    771:             nSend1++;
    772:           }
    773:         }
    774:         /* recieve requests, send response, clear lists */
    775:         kk     = nactive_edges;
    776:         MPIU_Allreduce(&kk,&nactive_edges,1,MPIU_INT,MPI_SUM,comm); /* not correct syncronization and global */
    777:         nSend2 = 0;
    778:         while (1) {
    779: #define BF_SZ 10000
    780:           PetscMPIInt flag,count;
    781:           PetscInt    rbuff[BF_SZ],*pt,*pt2,*pt3,count2,*sbuff,count3;
    782:           MPI_Request *request;

    784:           MPI_Iprobe(MPI_ANY_SOURCE, tag1, comm, &flag, &status);
    785:           if (!flag) break;
    786:           MPI_Get_count(&status, MPIU_INT, &count);
    787:           if (count > BF_SZ) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_SUP,"buffer too small for recieve: %d",count);
    788:           proc = status.MPI_SOURCE;
    789:           /* recieve request tag1 [n, proc, n*[gid1,lid0] ] */
    790:           MPI_Recv(rbuff, count, MPIU_INT, proc, tag1, comm, &status);
    791:           /* count sends */
    792:           pt = rbuff; count3 = count2 = 0;
    793:           n  = *pt++; kk = *pt++;
    794:           while (n--) {
    795:             PetscInt gid1=*pt++, lid1=gid1-my0; kk=*pt++;
    796:             if (lid_matched[lid1]) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Recieved deleted gid %D, deleted by (lid) %D from proc %D\n",sub_it,gid1,kk);
    797:             lid_matched[lid1] = PETSC_TRUE; /* keep track of what we've done this round */
    798:             PetscCDSizeAt(agg_llists, lid1, &kk);
    799:             count2           += kk + 2;
    800:             count3++; /* number of verts requested (n) */
    801:           }
    802:           if (count2 > count3*CHUNCK_SIZE) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_SUP,"Irecv will be too small: %D",count2);
    803:           /* send tag2 *[lid0, n, n*[gid] ] */
    804:           PetscMalloc(count2*sizeof(PetscInt) + sizeof(MPI_Request), &sbuff);
    805:           request          = (MPI_Request*)sbuff;
    806:           sreqs2[nSend2++] = request; /* cache request */
    807:           if (nSend2==REQ_BF_SIZE) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_SUP,"buffer too small for requests: %D",nSend2);
    808:           pt2 = sbuff = (PetscInt*)(request+1);
    809:           pt  = rbuff;
    810:           n   = *pt++; kk = *pt++;
    811:           while (n--) {
    812:             /* read [n, proc, n*[gid1,lid0] */
    813:             PetscInt gid1=*pt++, lid1=gid1-my0, lid0=*pt++;
    814:             /* write [lid0, n, n*[gid] ] */
    815:             *pt2++ = lid0;
    816:             pt3    = pt2++; /* save pointer for later */
    817:             PetscCDGetHeadPos(agg_llists,lid1,&pos);
    818:             while (pos) {
    819:               PetscInt gid;
    820:               PetscCDIntNdGetID(pos, &gid);
    821:               PetscCDGetNextPos(agg_llists,lid1,&pos);
    822:               *pt2++ = gid;
    823:             }
    824:             *pt3 = (pt2-pt3)-1;
    825:             /* clear list */
    826:             PetscCDRemoveAll(agg_llists, lid1);
    827:           }
    828:           /* send requested data tag2 *[lid0, n, n*[gid1] ] */
    829:           MPI_Isend(sbuff, count2, MPIU_INT, proc, tag2, comm, request);
    830:         }

    832:         /* recieve tag2 *[lid0, n, n*[gid] ] */
    833:         for (kk=0; kk<nSend1; kk++) {
    834:           PetscMPIInt count;
    835:           MPI_Request *request;
    836:           PetscInt    *pt, *pt2;

    838:           request = rreqs2[kk]; /* no need to free -- buffer is in 'sbuffs1' */
    839:           MPI_Wait(request, &status);
    840:           MPI_Get_count(&status, MPIU_INT, &count);
    841:           pt      = pt2 = (PetscInt*)(request+1);
    842:           while (pt-pt2 < count) {
    843:             PetscInt lid0 = *pt++, n = *pt++;
    844:             while (n--) {
    845:               PetscInt gid1 = *pt++;
    846:               PetscCDAppendID(agg_llists, lid0, gid1);
    847:             }
    848:           }
    849:         }

    851:         /* wait for tag1 isends */
    852:         while (nSend1--) {
    853:           MPI_Request *request;
    854:           request = (MPI_Request*)sbuffs1[nSend1];
    855:           MPI_Wait(request, &status);
    856:           PetscFree(request);
    857:         }
    858:         PetscFree(sbuffs1);

    860:         /* wait for tag2 isends */
    861:         while (nSend2--) {
    862:           MPI_Request *request = sreqs2[nSend2];
    863:           MPI_Wait(request, &status);
    864:           PetscFree(request);
    865:         }

    867:         VecRestoreArray(ghostMaxEdge, &cpcol_max_ew);
    868:         VecRestoreArray(ghostMaxPE, &cpcol_max_pe);

    870:         /* get 'cpcol_matched' - use locMaxPE, ghostMaxEdge, cpcol_max_ew */
    871:         for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    872:           PetscScalar vval = lid_matched[kk] ? 1.0 : 0.0;
    873:           VecSetValues(locMaxPE, 1, &gid, &vval, INSERT_VALUES); /* set with GID */
    874:         }
    875:         VecAssemblyBegin(locMaxPE);
    876:         VecAssemblyEnd(locMaxPE);
    877:         VecScatterBegin(mpimat->Mvctx,locMaxPE,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    878:         VecScatterEnd(mpimat->Mvctx,locMaxPE,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    879:         VecGetArray(ghostMaxEdge, &cpcol_max_ew);
    880:         VecGetLocalSize(mpimat->lvec, &n);
    881:         for (kk=0; kk<n; kk++) {
    882:           cpcol_matched[kk] = (PetscBool)(PetscRealPart(cpcol_max_ew[kk]) != 0.0);
    883:         }
    884:         VecRestoreArray(ghostMaxEdge, &cpcol_max_ew);
    885:       } /* size > 1 */

    887:       /* compute 'locMaxEdge' */
    888:       VecRestoreArray(locMaxEdge, &lid_max_ew);
    889:       for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    890:         PetscReal max_e = 0.,tt;
    891:         PetscScalar vval;
    892:         PetscInt lid = kk;

    894:         if (lid_matched[lid]) vval = 0.;
    895:         else {
    896:           ii = matA->i; n = ii[lid+1] - ii[lid]; idx = matA->j + ii[lid];
    897:           ap = matA->a + ii[lid];
    898:           for (jj=0; jj<n; jj++) {
    899:             PetscInt lidj = idx[jj];
    900:             if (lid_matched[lidj]) continue; /* this is new - can change local max */
    901:             if (lidj != lid && PetscRealPart(ap[jj]) > max_e) max_e = PetscRealPart(ap[jj]);
    902:           }
    903:           if (lid_cprowID && (ix=lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
    904:             ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    905:             ap  = matB->a + ii[ix];
    906:             idx = matB->j + ii[ix];
    907:             for (jj=0; jj<n; jj++) {
    908:               PetscInt lidj = idx[jj];
    909:               if (cpcol_matched[lidj]) continue;
    910:               if ((tt=PetscRealPart(ap[jj])) > max_e) max_e = tt;
    911:             }
    912:           }
    913:         }
    914:         vval = (PetscScalar)max_e;
    915:         VecSetValues(locMaxEdge, 1, &gid, &vval, INSERT_VALUES); /* set with GID */
    916:       }
    917:       VecAssemblyBegin(locMaxEdge);
    918:       VecAssemblyEnd(locMaxEdge);

    920:       if (size>1 && sub_it != n_sub_its-1) {
    921:         /* compute 'cpcol_max_ew' */
    922:         VecScatterBegin(mpimat->Mvctx,locMaxEdge,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    923:         VecScatterEnd(mpimat->Mvctx,locMaxEdge,ghostMaxEdge,INSERT_VALUES,SCATTER_FORWARD);
    924:         VecGetArray(ghostMaxEdge, &cpcol_max_ew);
    925:         VecGetArray(locMaxEdge, &lid_max_ew);

    927:         /* compute 'cpcol_max_pe' */
    928:         for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    929:           PetscInt lid = kk;
    930:           PetscReal ew,v1_max_e,v0_max_e=PetscRealPart(lid_max_ew[lid]);
    931:           PetscScalar vval;
    932:           PetscMPIInt max_pe=rank,pe;

    934:           if (lid_matched[lid]) vval = (PetscScalar)rank;
    935:           else if ((ix=lid_cprowID[lid]) != -1) { /* if I have any ghost neighbors */
    936:             ii  = matB->compressedrow.i; n = ii[ix+1] - ii[ix];
    937:             ap  = matB->a + ii[ix];
    938:             idx = matB->j + ii[ix];
    939:             for (jj=0; jj<n; jj++) {
    940:               PetscInt lidj = idx[jj];
    941:               if (cpcol_matched[lidj]) continue;
    942:               ew = PetscRealPart(ap[jj]); v1_max_e = PetscRealPart(cpcol_max_ew[lidj]);
    943:               /* get max pe that has a max_e == to this edge w */
    944:               if ((pe=cpcol_pe[idx[jj]]) > max_pe && ew > v1_max_e - PETSC_SMALL && ew > v0_max_e - PETSC_SMALL) max_pe = pe;
    945:             }
    946:             vval = (PetscScalar)max_pe;
    947:           }
    948:           VecSetValues(locMaxPE, 1, &gid, &vval, INSERT_VALUES);
    949:         }
    950:         VecAssemblyBegin(locMaxPE);
    951:         VecAssemblyEnd(locMaxPE);

    953:         VecScatterBegin(mpimat->Mvctx,locMaxPE,ghostMaxPE,INSERT_VALUES,SCATTER_FORWARD);
    954:         VecScatterEnd(mpimat->Mvctx,locMaxPE,ghostMaxPE,INSERT_VALUES,SCATTER_FORWARD);
    955:         VecGetArray(ghostMaxPE, &cpcol_max_pe);
    956:         VecRestoreArray(locMaxEdge, &lid_max_ew);
    957:       } /* deal with deleted ghost */
    958:       PetscInfo3(a_Gmat,"\t %D.%D: %D active edges.\n",iter,sub_it,nactive_edges);
    959:       if (!nactive_edges) break;
    960:     } /* sub_it loop */

    962:     /* clean up iteration */
    963:     PetscFree(Edges);
    964:     if (mpimat) {
    965:       VecRestoreArray(ghostMaxEdge, &cpcol_max_ew);
    966:       VecDestroy(&ghostMaxEdge);
    967:       VecRestoreArray(ghostMaxPE, &cpcol_max_pe);
    968:       VecDestroy(&ghostMaxPE);
    969:       PetscFree(cpcol_pe);
    970:       PetscFree(cpcol_matched);
    971:     }

    973:     VecDestroy(&locMaxEdge);
    974:     VecDestroy(&locMaxPE);

    976:     if (mpimat) {
    977:       VecRestoreArray(mpimat->lvec, &cpcol_gid);
    978:     }

    980:     /* create next G if needed */
    981:     if (iter == n_iter) { /* hard wired test - need to look at full surrounded nodes or something */
    982:       MatDestroy(&P);
    983:       MatDestroy(&cMat);
    984:       break;
    985:     } else {
    986:       Vec diag;
    987:       /* add identity for unmatched vertices so they stay alive */
    988:       for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    989:         if (!lid_matched[kk]) {
    990:           gid  = kk+my0;
    991:           MatGetRow(cMat,gid,&n,0,0);
    992:           if (n>1) {
    993:             MatSetValues(P,1,&gid,1,&gid,&one,INSERT_VALUES);
    994:           }
    995:           MatRestoreRow(cMat,gid,&n,0,0);
    996:         }
    997:       }
    998:       MatAssemblyBegin(P,MAT_FINAL_ASSEMBLY);
    999:       MatAssemblyEnd(P,MAT_FINAL_ASSEMBLY);

    1001:       /* project to make new graph with colapsed edges */
    1002:       MatPtAP(cMat,P,MAT_INITIAL_MATRIX,1.0,&tMat);
    1003:       MatDestroy(&P);
    1004:       MatDestroy(&cMat);
    1005:       cMat = tMat;
    1006:       MatCreateVecs(cMat, &diag, 0);
    1007:       MatGetDiagonal(cMat, diag); /* effectively PCJACOBI */
    1008:       VecReciprocal(diag);
    1009:       VecSqrtAbs(diag);
    1010:       MatDiagonalScale(cMat, diag, diag);
    1011:       VecDestroy(&diag);
    1012:     }
    1013:   } /* coarsen iterator */

    1015:   /* make fake matrix */
    1016:   if (size>1) {
    1017:     Mat          mat;
    1018:     PetscCDIntNd *pos;
    1019:     PetscInt     gid, NN, MM, jj = 0, mxsz = 0;

    1021:     for (kk=0; kk<nloc; kk++) {
    1022:       PetscCDSizeAt(agg_llists, kk, &jj);
    1023:       if (jj > mxsz) mxsz = jj;
    1024:     }
    1025:     MatGetSize(a_Gmat, &MM, &NN);
    1026:     if (mxsz > MM-nloc) mxsz = MM-nloc;

    1028:     MatCreateAIJ(comm, nloc, nloc,PETSC_DETERMINE, PETSC_DETERMINE,0, 0, mxsz, 0, &mat);

    1030:     for (kk=0,gid=my0; kk<nloc; kk++,gid++) {
    1031:       /* for (pos=PetscCDGetHeadPos(agg_llists,kk) ; pos ; pos=PetscCDGetNextPos(agg_llists,kk,pos)) { */
    1032:       PetscCDGetHeadPos(agg_llists,kk,&pos);
    1033:       while (pos) {
    1034:         PetscInt gid1;
    1035:         PetscCDIntNdGetID(pos, &gid1);
    1036:         PetscCDGetNextPos(agg_llists,kk,&pos);

    1038:         if (gid1 < my0 || gid1 >= my0+nloc) {
    1039:           MatSetValues(mat,1,&gid,1,&gid1,&one,ADD_VALUES);
    1040:         }
    1041:       }
    1042:     }
    1043:     MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);
    1044:     MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);
    1045:     PetscCDSetMat(agg_llists, mat);
    1046:   }

    1048:   PetscFree(lid_cprowID);
    1049:   PetscFree(lid_gid);
    1050:   PetscFree(lid_matched);
    1051:   PetscCDDestroy(deleted_list);
    1052:   return(0);
    1053: }

    1055: typedef struct {
    1056:   int dummy;
    1057: } MatCoarsen_HEM;
    1058: /*
    1059:    HEM coarsen, simple greedy.
    1060: */
    1061: static PetscErrorCode MatCoarsenApply_HEM(MatCoarsen coarse)
    1062: {
    1063:   /* MatCoarsen_HEM *HEM = (MatCoarsen_HEM*)coarse->subctx; */
    1065:   Mat            mat = coarse->graph;

    1069:   if (!coarse->perm) {
    1070:     IS       perm;
    1071:     PetscInt n,m;

    1073:     MatGetLocalSize(mat, &m, &n);
    1074:     ISCreateStride(PetscObjectComm((PetscObject)mat), m, 0, 1, &perm);
    1075:     heavyEdgeMatchAgg(perm, mat, &coarse->agg_lists);
    1076:     ISDestroy(&perm);
    1077:   } else {
    1078:     heavyEdgeMatchAgg(coarse->perm, mat, &coarse->agg_lists);
    1079:   }
    1080:   return(0);
    1081: }

    1083: static PetscErrorCode MatCoarsenView_HEM(MatCoarsen coarse,PetscViewer viewer)
    1084: {
    1085:   /* MatCoarsen_HEM *HEM = (MatCoarsen_HEM*)coarse->subctx; */
    1087:   PetscMPIInt    rank;
    1088:   PetscBool      iascii;

    1092:   MPI_Comm_rank(PetscObjectComm((PetscObject)coarse),&rank);
    1093:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    1094:   if (iascii) {
    1095:     PetscViewerASCIIPushSynchronized(viewer);
    1096:     PetscViewerASCIISynchronizedPrintf(viewer,"  [%d] HEM aggregator\n",rank);
    1097:     PetscViewerFlush(viewer);
    1098:     PetscViewerASCIIPopSynchronized(viewer);
    1099:   }
    1100:   return(0);
    1101: }

    1103: static PetscErrorCode MatCoarsenDestroy_HEM(MatCoarsen coarse)
    1104: {
    1105:   MatCoarsen_HEM *HEM = (MatCoarsen_HEM*)coarse->subctx;

    1110:   PetscFree(HEM);
    1111:   return(0);
    1112: }

    1114: /*MC
    1115:    MATCOARSENHEM - A coarsener that uses HEM a simple greedy coarsener

    1117:    Level: beginner

    1119: .keywords: Coarsen, create, context

    1121: .seealso: MatCoarsenSetType(), MatCoarsenType, MatCoarsenCreate()

    1123: M*/

    1125: PETSC_EXTERN PetscErrorCode MatCoarsenCreate_HEM(MatCoarsen coarse)
    1126: {
    1128:   MatCoarsen_HEM *HEM;

    1131:   PetscNewLog(coarse,&HEM);
    1132:   coarse->subctx       = (void*)HEM;
    1133:   coarse->ops->apply   = MatCoarsenApply_HEM;
    1134:   coarse->ops->view    = MatCoarsenView_HEM;
    1135:   coarse->ops->destroy = MatCoarsenDestroy_HEM;
    1136:   return(0);
    1137: }