Date: 2022-08-02T03:14:36+00:00

Actual source code: util.c

      1: /*
      2:  GAMG geometric-algebric multigrid PC - Mark Adams 2011
      3:  */
      4: #include <petsc/private/matimpl.h>
      5: #include <../src/ksp/pc/impls/gamg/gamg.h>
      6: #include <petsc/private/kspimpl.h>

      8: /*
      9:    Produces a set of block column indices of the matrix row, one for each block represented in the original row

     11:    n - the number of block indices in cc[]
     12:    cc - the block indices (must be large enough to contain the indices)
     13: */
     14: static inline PetscErrorCode MatCollapseRow(Mat Amat,PetscInt row,PetscInt bs,PetscInt *n,PetscInt *cc)
     15: {
     16:   PetscInt       cnt = -1,nidx,j;
     17:   const PetscInt *idx;

     19:   MatGetRow(Amat,row,&nidx,&idx,NULL);
     20:   if (nidx) {
     21:     cnt = 0;
     22:     cc[cnt] = idx[0]/bs;
     23:     for (j=1; j<nidx; j++) {
     24:       if (cc[cnt] < idx[j]/bs) cc[++cnt] = idx[j]/bs;
     25:     }
     26:   }
     27:   MatRestoreRow(Amat,row,&nidx,&idx,NULL);
     28:   *n = cnt+1;
     29:   return 0;
     30: }

     32: /*
     33:     Produces a set of block column indices of the matrix block row, one for each block represented in the original set of rows

     35:     ncollapsed - the number of block indices
     36:     collapsed - the block indices (must be large enough to contain the indices)
     37: */
     38: static inline PetscErrorCode MatCollapseRows(Mat Amat,PetscInt start,PetscInt bs,PetscInt *w0,PetscInt *w1,PetscInt *w2,PetscInt *ncollapsed,PetscInt **collapsed)
     39: {
     40:   PetscInt       i,nprev,*cprev = w0,ncur = 0,*ccur = w1,*merged = w2,*cprevtmp;

     42:   MatCollapseRow(Amat,start,bs,&nprev,cprev);
     43:   for (i=start+1; i<start+bs; i++) {
     44:     MatCollapseRow(Amat,i,bs,&ncur,ccur);
     45:     PetscMergeIntArray(nprev,cprev,ncur,ccur,&nprev,&merged);
     46:     cprevtmp = cprev; cprev = merged; merged = cprevtmp;
     47:   }
     48:   *ncollapsed = nprev;
     49:   if (collapsed) *collapsed  = cprev;
     50:   return 0;
     51: }

     53: /* -------------------------------------------------------------------------- */
     54: /*
     55:    PCGAMGCreateGraph - create simple scaled scalar graph from matrix

     57:  Input Parameter:
     58:  . Amat - matrix
     59:  Output Parameter:
     60:  . a_Gmaat - eoutput scalar graph (symmetric?)
     61:  */
     62: PetscErrorCode PCGAMGCreateGraph(Mat Amat, Mat *a_Gmat)
     63: {
     64:   PetscInt       Istart,Iend,Ii,jj,kk,ncols,nloc,NN,MM,bs;
     65:   MPI_Comm       comm;
     66:   Mat            Gmat;
     67:   PetscBool      ismpiaij,isseqaij;

     69:   PetscObjectGetComm((PetscObject)Amat,&comm);
     70:   MatGetOwnershipRange(Amat, &Istart, &Iend);
     71:   MatGetSize(Amat, &MM, &NN);
     72:   MatGetBlockSize(Amat, &bs);
     73:   nloc = (Iend-Istart)/bs;

     75:   PetscObjectBaseTypeCompare((PetscObject)Amat,MATSEQAIJ,&isseqaij);
     76:   PetscObjectBaseTypeCompare((PetscObject)Amat,MATMPIAIJ,&ismpiaij);
     78:   PetscLogEventBegin(petsc_gamg_setup_events[GRAPH],0,0,0,0);

     80:   /* TODO GPU: these calls are potentially expensive if matrices are large and we want to use the GPU */
     81:   /* A solution consists in providing a new API, MatAIJGetCollapsedAIJ, and each class can provide a fast
     82:      implementation */
     83:   MatViewFromOptions(Amat, NULL, "-g_mat_view");
     84:   if (bs > 1 && (isseqaij || ((Mat_MPIAIJ*)Amat->data)->garray)) {
     85:     PetscInt  *d_nnz, *o_nnz;
     86:     Mat       a, b, c;
     87:     MatScalar *aa,val,AA[4096];
     88:     PetscInt  *aj,*ai,AJ[4096],nc;
     89:     PetscInfo(Amat,"New bs>1 PCGAMGCreateGraph. nloc=%D\n",nloc);
     90:     if (isseqaij) {
     91:       a = Amat; b = NULL;
     92:     }
     93:     else {
     94:       Mat_MPIAIJ *d = (Mat_MPIAIJ*)Amat->data;
     95:       a = d->A; b = d->B;
     96:     }
     97:     PetscMalloc2(nloc, &d_nnz,isseqaij ? 0 : nloc, &o_nnz);
     98:     for (c=a, kk=0 ; c && kk<2 ; c=b, kk++){
     99:       PetscInt       *nnz = (c==a) ? d_nnz : o_nnz, nmax=0;
    100:       const PetscInt *cols;
    101:       for (PetscInt brow=0,jj,ok=1,j0; brow < nloc*bs; brow += bs) { // block rows
    102:         MatGetRow(c,brow,&jj,&cols,NULL);
    103:         nnz[brow/bs] = jj/bs;
    104:         if (jj%bs) ok = 0;
    105:         if (cols) j0 = cols[0];
    106:         else j0 = -1;
    107:         MatRestoreRow(c,brow,&jj,&cols,NULL);
    108:         if (nnz[brow/bs]>nmax) nmax = nnz[brow/bs];
    109:         for (PetscInt ii=1; ii < bs && nnz[brow/bs] ; ii++) { // check for non-dense blocks
    110:           MatGetRow(c,brow+ii,&jj,&cols,NULL);
    111:           if (jj%bs) ok = 0;
    112:           if ((cols && j0 != cols[0]) || (!cols && j0 != -1)) ok = 0;
    113:           if (nnz[brow/bs] != jj/bs) ok = 0;
    114:           MatRestoreRow(c,brow+ii,&jj,&cols,NULL);
    115:         }
    116:         if (!ok) {
    117:           PetscFree2(d_nnz,o_nnz);
    118:           goto old_bs;
    119:         }
    120:       }
    122:     }
    123:     MatCreate(comm, &Gmat);
    124:     MatSetSizes(Gmat,nloc,nloc,PETSC_DETERMINE,PETSC_DETERMINE);
    125:     MatSetBlockSizes(Gmat, 1, 1);
    126:     MatSetType(Gmat, MATAIJ);
    127:     MatSeqAIJSetPreallocation(Gmat,0,d_nnz);
    128:     MatMPIAIJSetPreallocation(Gmat,0,d_nnz,0,o_nnz);
    129:     PetscFree2(d_nnz,o_nnz);
    130:     // diag
    131:     for (PetscInt brow=0,n,grow; brow < nloc*bs; brow += bs) { // block rows
    132:       Mat_SeqAIJ *aseq  = (Mat_SeqAIJ*)a->data;
    133:       ai = aseq->i;
    134:       n  = ai[brow+1] - ai[brow];
    135:       aj = aseq->j + ai[brow];
    136:       for (int k=0; k<n; k += bs) { // block columns
    137:         AJ[k/bs] = aj[k]/bs + Istart/bs; // diag starts at (Istart,Istart)
    138:         val = 0;
    139:         for (int ii=0; ii<bs; ii++) { // rows in block
    140:           aa = aseq->a + ai[brow+ii] + k;
    141:           for (int jj=0; jj<bs; jj++) { // columns in block
    142:             val += PetscAbs(PetscRealPart(aa[jj])); // a sort of norm
    143:           }
    144:         }
    145:         AA[k/bs] = val;
    146:       }
    147:       grow = Istart/bs + brow/bs;
    148:       MatSetValues(Gmat,1,&grow,n/bs,AJ,AA,INSERT_VALUES);
    149:     }
    150:     // off-diag
    151:     if (ismpiaij) {
    152:       Mat_MPIAIJ        *aij = (Mat_MPIAIJ*)Amat->data;
    153:       const PetscScalar *vals;
    154:       const PetscInt    *cols, *garray = aij->garray;
    156:       for (PetscInt brow=0,grow; brow < nloc*bs; brow += bs) { // block rows
    157:         MatGetRow(b,brow,&ncols,&cols,NULL);
    158:         for (int k=0,cidx=0; k<ncols; k += bs,cidx++) {
    159:           AA[k/bs] = 0;
    160:           AJ[cidx] = garray[cols[k]]/bs;
    161:         }
    162:         nc = ncols/bs;
    163:         MatRestoreRow(b,brow,&ncols,&cols,NULL);
    164:         for (int ii=0; ii<bs; ii++) { // rows in block
    165:           MatGetRow(b,brow+ii,&ncols,&cols,&vals);
    166:           for (int k=0; k<ncols; k += bs) {
    167:             for (int jj=0; jj<bs; jj++) { // cols in block
    168:               AA[k/bs] += PetscAbs(PetscRealPart(vals[k+jj]));
    169:             }
    170:           }
    171:           MatRestoreRow(b,brow+ii,&ncols,&cols,&vals);
    172:         }
    173:         grow = Istart/bs + brow/bs;
    174:         MatSetValues(Gmat,1,&grow,nc,AJ,AA,INSERT_VALUES);
    175:       }
    176:     }
    177:     MatAssemblyBegin(Gmat,MAT_FINAL_ASSEMBLY);
    178:     MatAssemblyEnd(Gmat,MAT_FINAL_ASSEMBLY);
    179:     MatViewFromOptions(Gmat, NULL, "-g_mat_view");
    180:   } else if (bs > 1) {
    181:     const PetscScalar *vals;
    182:     const PetscInt    *idx;
    183:     PetscInt          *d_nnz, *o_nnz,*w0,*w1,*w2;

    185: old_bs:
    186:     /*
    187:        Determine the preallocation needed for the scalar matrix derived from the vector matrix.
    188:     */

    190:     PetscInfo(Amat,"OLD bs>1 PCGAMGCreateGraph\n");
    191:     PetscObjectBaseTypeCompare((PetscObject)Amat,MATSEQAIJ,&isseqaij);
    192:     PetscObjectBaseTypeCompare((PetscObject)Amat,MATMPIAIJ,&ismpiaij);
    193:     PetscMalloc2(nloc, &d_nnz,isseqaij ? 0 : nloc, &o_nnz);

    195:     if (isseqaij) {
    196:       PetscInt max_d_nnz;

    198:       /*
    199:           Determine exact preallocation count for (sequential) scalar matrix
    200:       */
    201:       MatSeqAIJGetMaxRowNonzeros(Amat,&max_d_nnz);
    202:       max_d_nnz = PetscMin(nloc,bs*max_d_nnz);
    203:       PetscMalloc3(max_d_nnz, &w0,max_d_nnz, &w1,max_d_nnz, &w2);
    204:       for (Ii = 0, jj = 0; Ii < Iend; Ii += bs, jj++) {
    205:         MatCollapseRows(Amat,Ii,bs,w0,w1,w2,&d_nnz[jj],NULL);
    206:       }
    207:       PetscFree3(w0,w1,w2);

    209:     } else if (ismpiaij) {
    210:       Mat            Daij,Oaij;
    211:       const PetscInt *garray;
    212:       PetscInt       max_d_nnz;

    214:       MatMPIAIJGetSeqAIJ(Amat,&Daij,&Oaij,&garray);

    216:       /*
    217:           Determine exact preallocation count for diagonal block portion of scalar matrix
    218:       */
    219:       MatSeqAIJGetMaxRowNonzeros(Daij,&max_d_nnz);
    220:       max_d_nnz = PetscMin(nloc,bs*max_d_nnz);
    221:       PetscMalloc3(max_d_nnz, &w0,max_d_nnz, &w1,max_d_nnz, &w2);
    222:       for (Ii = 0, jj = 0; Ii < Iend - Istart; Ii += bs, jj++) {
    223:         MatCollapseRows(Daij,Ii,bs,w0,w1,w2,&d_nnz[jj],NULL);
    224:       }
    225:       PetscFree3(w0,w1,w2);

    227:       /*
    228:          Over estimate (usually grossly over), preallocation count for off-diagonal portion of scalar matrix
    229:       */
    230:       for (Ii = 0, jj = 0; Ii < Iend - Istart; Ii += bs, jj++) {
    231:         o_nnz[jj] = 0;
    232:         for (kk=0; kk<bs; kk++) { /* rows that get collapsed to a single row */
    233:           MatGetRow(Oaij,Ii+kk,&ncols,NULL,NULL);
    234:           o_nnz[jj] += ncols;
    235:           MatRestoreRow(Oaij,Ii+kk,&ncols,NULL,NULL);
    236:         }
    237:         if (o_nnz[jj] > (NN/bs-nloc)) o_nnz[jj] = NN/bs-nloc;
    238:       }

    240:     } else SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Require AIJ matrix type");

    242:     /* get scalar copy (norms) of matrix */
    243:     MatCreate(comm, &Gmat);
    244:     MatSetSizes(Gmat,nloc,nloc,PETSC_DETERMINE,PETSC_DETERMINE);
    245:     MatSetBlockSizes(Gmat, 1, 1);
    246:     MatSetType(Gmat, MATAIJ);
    247:     MatSeqAIJSetPreallocation(Gmat,0,d_nnz);
    248:     MatMPIAIJSetPreallocation(Gmat,0,d_nnz,0,o_nnz);
    249:     PetscFree2(d_nnz,o_nnz);

    251:     for (Ii = Istart; Ii < Iend; Ii++) {
    252:       PetscInt dest_row = Ii/bs;
    253:       MatGetRow(Amat,Ii,&ncols,&idx,&vals);
    254:       for (jj=0; jj<ncols; jj++) {
    255:         PetscInt    dest_col = idx[jj]/bs;
    256:         PetscScalar sv       = PetscAbs(PetscRealPart(vals[jj]));
    257:         MatSetValues(Gmat,1,&dest_row,1,&dest_col,&sv,ADD_VALUES);
    258:       }
    259:       MatRestoreRow(Amat,Ii,&ncols,&idx,&vals);
    260:     }
    261:     MatAssemblyBegin(Gmat,MAT_FINAL_ASSEMBLY);
    262:     MatAssemblyEnd(Gmat,MAT_FINAL_ASSEMBLY);
    263:     MatViewFromOptions(Gmat, NULL, "-g_mat_view");
    264:   } else {
    265:     /* just copy scalar matrix - abs() not taken here but scaled later */
    266:     MatDuplicate(Amat, MAT_COPY_VALUES, &Gmat);
    267:   }
    268:   MatPropagateSymmetryOptions(Amat, Gmat);

    270:   PetscLogEventEnd(petsc_gamg_setup_events[GRAPH],0,0,0,0);

    272:   *a_Gmat = Gmat;
    273:   return 0;
    274: }

    276: /* -------------------------------------------------------------------------- */
    277: /*@C
    278:    PCGAMGFilterGraph - filter (remove zero and possibly small values from the) graph and make it symmetric if requested

    280:    Collective on Mat

    282:    Input Parameters:
    283: +   a_Gmat - the graph
    284: .   vfilter - threshold parameter [0,1)
    285: -   symm - make the result symmetric

    287:    Level: developer

    289:    Notes:
    290:     This is called before graph coarsers are called.

    292: .seealso: PCGAMGSetThreshold()
    293: @*/
    294: PetscErrorCode PCGAMGFilterGraph(Mat *a_Gmat,PetscReal vfilter,PetscBool symm)
    295: {
    296:   PetscInt          Istart,Iend,Ii,jj,ncols,nnz0,nnz1, NN, MM, nloc;
    297:   PetscMPIInt       rank;
    298:   Mat               Gmat  = *a_Gmat, tGmat;
    299:   MPI_Comm          comm;
    300:   const PetscScalar *vals;
    301:   const PetscInt    *idx;
    302:   PetscInt          *d_nnz, *o_nnz;
    303:   Vec               diag;

    305:   PetscLogEventBegin(petsc_gamg_setup_events[SET16],0,0,0,0);

    307:   /* TODO GPU: optimization proposal, each class provides fast implementation of this
    308:      procedure via MatAbs API */
    309:   if (vfilter < 0.0 && !symm) {
    310:     /* Just use the provided matrix as the graph but make all values positive */
    311:     MatInfo     info;
    312:     PetscScalar *avals;
    313:     PetscBool isaij,ismpiaij;
    314:     PetscObjectBaseTypeCompare((PetscObject)Gmat,MATSEQAIJ,&isaij);
    315:     PetscObjectBaseTypeCompare((PetscObject)Gmat,MATMPIAIJ,&ismpiaij);
    317:     if (isaij) {
    318:       MatGetInfo(Gmat,MAT_LOCAL,&info);
    319:       MatSeqAIJGetArray(Gmat,&avals);
    320:       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
    321:       MatSeqAIJRestoreArray(Gmat,&avals);
    322:     } else {
    323:       Mat_MPIAIJ  *aij = (Mat_MPIAIJ*)Gmat->data;
    324:       MatGetInfo(aij->A,MAT_LOCAL,&info);
    325:       MatSeqAIJGetArray(aij->A,&avals);
    326:       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
    327:       MatSeqAIJRestoreArray(aij->A,&avals);
    328:       MatGetInfo(aij->B,MAT_LOCAL,&info);
    329:       MatSeqAIJGetArray(aij->B,&avals);
    330:       for (jj = 0; jj<info.nz_used; jj++) avals[jj] = PetscAbsScalar(avals[jj]);
    331:       MatSeqAIJRestoreArray(aij->B,&avals);
    332:     }
    333:     PetscLogEventEnd(petsc_gamg_setup_events[SET16],0,0,0,0);
    334:     return 0;
    335:   }

    337:   /* TODO GPU: this can be called when filter = 0 -> Probably provide MatAIJThresholdCompress that compresses the entries below a threshold?
    338:                Also, if the matrix is symmetric, can we skip this
    339:                operation? It can be very expensive on large matrices. */
    340:   PetscObjectGetComm((PetscObject)Gmat,&comm);
    341:   MPI_Comm_rank(comm,&rank);
    342:   MatGetOwnershipRange(Gmat, &Istart, &Iend);
    343:   nloc = Iend - Istart;
    344:   MatGetSize(Gmat, &MM, &NN);

    346:   if (symm) {
    347:     Mat matTrans;
    348:     MatTranspose(Gmat, MAT_INITIAL_MATRIX, &matTrans);
    349:     MatAXPY(Gmat, 1.0, matTrans, Gmat->structurally_symmetric ? SAME_NONZERO_PATTERN : DIFFERENT_NONZERO_PATTERN);
    350:     MatDestroy(&matTrans);
    351:   }

    353:   /* scale Gmat for all values between -1 and 1 */
    354:   MatCreateVecs(Gmat, &diag, NULL);
    355:   MatGetDiagonal(Gmat, diag);
    356:   VecReciprocal(diag);
    357:   VecSqrtAbs(diag);
    358:   MatDiagonalScale(Gmat, diag, diag);
    359:   VecDestroy(&diag);

    361:   /* Determine upper bound on nonzeros needed in new filtered matrix */
    362:   PetscMalloc2(nloc, &d_nnz,nloc, &o_nnz);
    363:   for (Ii = Istart, jj = 0; Ii < Iend; Ii++, jj++) {
    364:     MatGetRow(Gmat,Ii,&ncols,NULL,NULL);
    365:     d_nnz[jj] = ncols;
    366:     o_nnz[jj] = ncols;
    367:     MatRestoreRow(Gmat,Ii,&ncols,NULL,NULL);
    368:     if (d_nnz[jj] > nloc) d_nnz[jj] = nloc;
    369:     if (o_nnz[jj] > (MM-nloc)) o_nnz[jj] = MM - nloc;
    370:   }
    371:   MatCreate(comm, &tGmat);
    372:   MatSetSizes(tGmat,nloc,nloc,MM,MM);
    373:   MatSetBlockSizes(tGmat, 1, 1);
    374:   MatSetType(tGmat, MATAIJ);
    375:   MatSeqAIJSetPreallocation(tGmat,0,d_nnz);
    376:   MatMPIAIJSetPreallocation(tGmat,0,d_nnz,0,o_nnz);
    377:   MatSetOption(tGmat,MAT_NO_OFF_PROC_ENTRIES,PETSC_TRUE);
    378:   PetscFree2(d_nnz,o_nnz);

    380:   for (Ii = Istart, nnz0 = nnz1 = 0; Ii < Iend; Ii++) {
    381:     MatGetRow(Gmat,Ii,&ncols,&idx,&vals);
    382:     for (jj=0; jj<ncols; jj++,nnz0++) {
    383:       PetscScalar sv = PetscAbs(PetscRealPart(vals[jj]));
    384:       if (PetscRealPart(sv) > vfilter) {
    385:         nnz1++;
    386:         MatSetValues(tGmat,1,&Ii,1,&idx[jj],&sv,INSERT_VALUES);
    387:       }
    388:     }
    389:     MatRestoreRow(Gmat,Ii,&ncols,&idx,&vals);
    390:   }
    391:   MatAssemblyBegin(tGmat,MAT_FINAL_ASSEMBLY);
    392:   MatAssemblyEnd(tGmat,MAT_FINAL_ASSEMBLY);
    393:   if (symm) {
    394:     MatSetOption(tGmat,MAT_SYMMETRIC,PETSC_TRUE);
    395:   } else {
    396:     MatPropagateSymmetryOptions(Gmat,tGmat);
    397:   }
    398:   PetscLogEventEnd(petsc_gamg_setup_events[SET16],0,0,0,0);

    400: #if defined(PETSC_USE_INFO)
    401:   {
    402:     double t1 = (!nnz0) ? 1. : 100.*(double)nnz1/(double)nnz0, t2 = (!nloc) ? 1. : (double)nnz0/(double)nloc;
    403:     PetscInfo(*a_Gmat,"\t %g%% nnz after filtering, with threshold %g, %g nnz ave. (N=%D)\n",t1,vfilter,t2,MM);
    404:   }
    405: #endif
    406:   MatDestroy(&Gmat);
    407:   *a_Gmat = tGmat;
    408:   return 0;
    409: }

    411: /* -------------------------------------------------------------------------- */
    412: /*
    413:    PCGAMGGetDataWithGhosts - hacks into Mat MPIAIJ so this must have size > 1

    415:    Input Parameter:
    416:    . Gmat - MPIAIJ matrix for scattters
    417:    . data_sz - number of data terms per node (# cols in output)
    418:    . data_in[nloc*data_sz] - column oriented data
    419:    Output Parameter:
    420:    . a_stride - numbrt of rows of output
    421:    . a_data_out[stride*data_sz] - output data with ghosts
    422: */
    423: PetscErrorCode PCGAMGGetDataWithGhosts(Mat Gmat,PetscInt data_sz,PetscReal data_in[],PetscInt *a_stride,PetscReal **a_data_out)
    424: {
    425:   Vec            tmp_crds;
    426:   Mat_MPIAIJ     *mpimat = (Mat_MPIAIJ*)Gmat->data;
    427:   PetscInt       nnodes,num_ghosts,dir,kk,jj,my0,Iend,nloc;
    428:   PetscScalar    *data_arr;
    429:   PetscReal      *datas;
    430:   PetscBool      isMPIAIJ;

    432:   PetscObjectBaseTypeCompare((PetscObject)Gmat, MATMPIAIJ, &isMPIAIJ);
    433:   MatGetOwnershipRange(Gmat, &my0, &Iend);
    434:   nloc      = Iend - my0;
    435:   VecGetLocalSize(mpimat->lvec, &num_ghosts);
    436:   nnodes    = num_ghosts + nloc;
    437:   *a_stride = nnodes;
    438:   MatCreateVecs(Gmat, &tmp_crds, NULL);

    440:   PetscMalloc1(data_sz*nnodes, &datas);
    441:   for (dir=0; dir<data_sz; dir++) {
    442:     /* set local, and global */
    443:     for (kk=0; kk<nloc; kk++) {
    444:       PetscInt    gid = my0 + kk;
    445:       PetscScalar crd = (PetscScalar)data_in[dir*nloc + kk]; /* col oriented */
    446:       datas[dir*nnodes + kk] = PetscRealPart(crd);

    448:       VecSetValues(tmp_crds, 1, &gid, &crd, INSERT_VALUES);
    449:     }
    450:     VecAssemblyBegin(tmp_crds);
    451:     VecAssemblyEnd(tmp_crds);
    452:     /* get ghost datas */
    453:     VecScatterBegin(mpimat->Mvctx,tmp_crds,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    454:     VecScatterEnd(mpimat->Mvctx,tmp_crds,mpimat->lvec,INSERT_VALUES,SCATTER_FORWARD);
    455:     VecGetArray(mpimat->lvec, &data_arr);
    456:     for (kk=nloc,jj=0;jj<num_ghosts;kk++,jj++) datas[dir*nnodes + kk] = PetscRealPart(data_arr[jj]);
    457:     VecRestoreArray(mpimat->lvec, &data_arr);
    458:   }
    459:   VecDestroy(&tmp_crds);
    460:   *a_data_out = datas;
    461:   return 0;
    462: }

    464: PetscErrorCode PCGAMGHashTableCreate(PetscInt a_size, PCGAMGHashTable *a_tab)
    465: {
    466:   PetscInt       kk;

    468:   a_tab->size = a_size;
    469:   PetscMalloc2(a_size, &a_tab->table,a_size, &a_tab->data);
    470:   for (kk=0; kk<a_size; kk++) a_tab->table[kk] = -1;
    471:   return 0;
    472: }

    474: PetscErrorCode PCGAMGHashTableDestroy(PCGAMGHashTable *a_tab)
    475: {
    476:   PetscFree2(a_tab->table,a_tab->data);
    477:   return 0;
    478: }

    480: PetscErrorCode PCGAMGHashTableAdd(PCGAMGHashTable *a_tab, PetscInt a_key, PetscInt a_data)
    481: {
    482:   PetscInt kk,idx;

    485:   for (kk = 0, idx = GAMG_HASH(a_key); kk < a_tab->size; kk++, idx = (idx==(a_tab->size-1)) ? 0 : idx + 1) {
    486:     if (a_tab->table[idx] == a_key) {
    487:       /* exists */
    488:       a_tab->data[idx] = a_data;
    489:       break;
    490:     } else if (a_tab->table[idx] == -1) {
    491:       /* add */
    492:       a_tab->table[idx] = a_key;
    493:       a_tab->data[idx]  = a_data;
    494:       break;
    495:     }
    496:   }
    497:   if (kk==a_tab->size) {
    498:     /* this is not to efficient, waiting until completely full */
    499:     PetscInt       oldsize = a_tab->size, new_size = 2*a_tab->size + 5, *oldtable = a_tab->table, *olddata = a_tab->data;

    501:     a_tab->size = new_size;
    502:     PetscMalloc2(a_tab->size, &a_tab->table,a_tab->size, &a_tab->data);
    503:     for (kk=0;kk<a_tab->size;kk++) a_tab->table[kk] = -1;
    504:     for (kk=0;kk<oldsize;kk++) {
    505:       if (oldtable[kk] != -1) {
    506:         PCGAMGHashTableAdd(a_tab, oldtable[kk], olddata[kk]);
    507:        }
    508:     }
    509:     PetscFree2(oldtable,olddata);
    510:     PCGAMGHashTableAdd(a_tab, a_key, a_data);
    511:   }
    512:   return 0;
    513: }