Date: 2026-03-01T05:24:57+00:00

Actual source code: spbas.c

      1: #include <../src/mat/impls/aij/seq/aij.h>
      2: #include <../src/mat/impls/aij/seq/bas/spbas.h>

      4: /*MC
      5:   MATSOLVERBAS -  Provides ICC(k) with drop tolerance

      7:   Works with `MATAIJ`  matrices

      9:   Options Database Keys:
     10: + -pc_factor_levels <l> - number of levels of fill
     11: - -pc_factor_drop_tolerance - is not currently hooked up to do anything

     13:   Level: intermediate

     15:    Contributed by: Bas van 't Hof

     17:    Note:
     18:     Since this currently hooked up to use drop tolerance it should produce the same factors and hence convergence as the PETSc ICC, for higher
     19:      levels of fill it does not. This needs to be investigated. Unless you are interested in drop tolerance ICC and willing to work through the code
     20:      we recommend not using this functionality.

     22: .seealso: [](ch_matrices), `Mat`, `PCFactorSetMatSolverType()`, `MatSolverType`, `PCFactorSetLevels()`, `PCFactorSetDropTolerance()`
     23: M*/

     25: /*
     26:   spbas_memory_requirement:
     27:     Calculate the number of bytes needed to store the matrix
     28: */
     29: size_t spbas_memory_requirement(spbas_matrix matrix)
     30: {
     31:   size_t memreq = 6 * sizeof(PetscInt) +             /* nrows, ncols, nnz, n_alloc_icol, n_alloc_val, col_idx_type */
     32:                   sizeof(PetscBool) +                /* block_data */
     33:                   sizeof(PetscScalar **) +           /* values */
     34:                   sizeof(PetscScalar *) +            /* alloc_val */
     35:                   2 * sizeof(PetscInt **) +          /* icols, icols0 */
     36:                   2 * sizeof(PetscInt *) +           /* row_nnz, alloc_icol */
     37:                   matrix.nrows * sizeof(PetscInt) +  /* row_nnz[*] */
     38:                   matrix.nrows * sizeof(PetscInt *); /* icols[*] */

     40:   /* icol0[*] */
     41:   if (matrix.col_idx_type == SPBAS_OFFSET_ARRAY) memreq += matrix.nrows * sizeof(PetscInt);

     43:   /* icols[*][*] */
     44:   if (matrix.block_data) memreq += matrix.n_alloc_icol * sizeof(PetscInt);
     45:   else memreq += matrix.nnz * sizeof(PetscInt);

     47:   if (matrix.values) {
     48:     memreq += matrix.nrows * sizeof(PetscScalar *); /* values[*] */
     49:     /* values[*][*] */
     50:     if (matrix.block_data) memreq += matrix.n_alloc_val * sizeof(PetscScalar);
     51:     else memreq += matrix.nnz * sizeof(PetscScalar);
     52:   }
     53:   return memreq;
     54: }

     56: /*
     57:   spbas_allocate_pattern:
     58:     allocate the pattern arrays row_nnz, icols and optionally values
     59: */
     60: static PetscErrorCode spbas_allocate_pattern(spbas_matrix *result, PetscBool do_values)
     61: {
     62:   PetscInt nrows        = result->nrows;
     63:   PetscInt col_idx_type = result->col_idx_type;

     65:   PetscFunctionBegin;
     66:   /* Allocate sparseness pattern */
     67:   PetscCall(PetscMalloc1(nrows, &result->row_nnz));
     68:   PetscCall(PetscMalloc1(nrows, &result->icols));

     70:   /* If offsets are given wrt an array, create array */
     71:   if (col_idx_type == SPBAS_OFFSET_ARRAY) {
     72:     PetscCall(PetscMalloc1(nrows, &result->icol0));
     73:   } else {
     74:     result->icol0 = NULL;
     75:   }

     77:   /* If values are given, allocate values array */
     78:   if (do_values) {
     79:     PetscCall(PetscMalloc1(nrows, &result->values));
     80:   } else {
     81:     result->values = NULL;
     82:   }
     83:   PetscFunctionReturn(PETSC_SUCCESS);
     84: }

     86: /*
     87: spbas_allocate_data:
     88:    in case of block_data:
     89:        Allocate the data arrays alloc_icol and optionally alloc_val,
     90:        set appropriate pointers from icols and values;
     91:    in case of !block_data:
     92:        Allocate the arrays icols[i] and optionally values[i]
     93: */
     94: static PetscErrorCode spbas_allocate_data(spbas_matrix *result)
     95: {
     96:   PetscInt  i;
     97:   PetscInt  nnz   = result->nnz;
     98:   PetscInt  nrows = result->nrows;
     99:   PetscInt  r_nnz;
    100:   PetscBool do_values  = (result->values) ? PETSC_TRUE : PETSC_FALSE;
    101:   PetscBool block_data = result->block_data;

    103:   PetscFunctionBegin;
    104:   if (block_data) {
    105:     /* Allocate the column number array and point to it */
    106:     result->n_alloc_icol = nnz;

    108:     PetscCall(PetscMalloc1(nnz, &result->alloc_icol));

    110:     result->icols[0] = result->alloc_icol;
    111:     for (i = 1; i < nrows; i++) result->icols[i] = result->icols[i - 1] + result->row_nnz[i - 1];

    113:     /* Allocate the value array and point to it */
    114:     if (do_values) {
    115:       result->n_alloc_val = nnz;

    117:       PetscCall(PetscMalloc1(nnz, &result->alloc_val));

    119:       result->values[0] = result->alloc_val;
    120:       for (i = 1; i < nrows; i++) result->values[i] = result->values[i - 1] + result->row_nnz[i - 1];
    121:     }
    122:   } else {
    123:     for (i = 0; i < nrows; i++) {
    124:       r_nnz = result->row_nnz[i];
    125:       PetscCall(PetscMalloc1(r_nnz, &result->icols[i]));
    126:     }
    127:     if (do_values) {
    128:       for (i = 0; i < nrows; i++) {
    129:         r_nnz = result->row_nnz[i];
    130:         PetscCall(PetscMalloc1(r_nnz, &result->values[i]));
    131:       }
    132:     }
    133:   }
    134:   PetscFunctionReturn(PETSC_SUCCESS);
    135: }

    137: /*
    138:   spbas_row_order_icol
    139:      determine if row i1 should come
    140:        + before row i2 in the sorted rows (return -1),
    141:        + after (return 1)
    142:        + is identical (return 0).
    143: */
    144: static int spbas_row_order_icol(PetscInt i1, PetscInt i2, PetscInt *irow_in, PetscInt *icol_in, PetscInt col_idx_type)
    145: {
    146:   PetscInt  j;
    147:   PetscInt  nnz1  = irow_in[i1 + 1] - irow_in[i1];
    148:   PetscInt  nnz2  = irow_in[i2 + 1] - irow_in[i2];
    149:   PetscInt *icol1 = &icol_in[irow_in[i1]];
    150:   PetscInt *icol2 = &icol_in[irow_in[i2]];

    152:   if (nnz1 < nnz2) return -1;
    153:   if (nnz1 > nnz2) return 1;

    155:   if (col_idx_type == SPBAS_COLUMN_NUMBERS) {
    156:     for (j = 0; j < nnz1; j++) {
    157:       if (icol1[j] < icol2[j]) return -1;
    158:       if (icol1[j] > icol2[j]) return 1;
    159:     }
    160:   } else if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) {
    161:     for (j = 0; j < nnz1; j++) {
    162:       if (icol1[j] - i1 < icol2[j] - i2) return -1;
    163:       if (icol1[j] - i1 > icol2[j] - i2) return 1;
    164:     }
    165:   } else if (col_idx_type == SPBAS_OFFSET_ARRAY) {
    166:     for (j = 1; j < nnz1; j++) {
    167:       if (icol1[j] - icol1[0] < icol2[j] - icol2[0]) return -1;
    168:       if (icol1[j] - icol1[0] > icol2[j] - icol2[0]) return 1;
    169:     }
    170:   }
    171:   return 0;
    172: }

    174: /*
    175:   spbas_mergesort_icols:
    176:     return a sorting of the rows in which identical sparseness patterns are
    177:     next to each other
    178: */
    179: static PetscErrorCode spbas_mergesort_icols(PetscInt nrows, PetscInt *irow_in, PetscInt *icol_in, PetscInt col_idx_type, PetscInt *isort)
    180: {
    181:   PetscInt  istep;                /* Chunk-sizes of already sorted parts of arrays */
    182:   PetscInt  i, i1, i2;            /* Loop counters for (partly) sorted arrays */
    183:   PetscInt  istart, i1end, i2end; /* start of newly sorted array part, end of both  parts */
    184:   PetscInt *ialloc;               /* Allocated arrays */
    185:   PetscInt *iswap;                /* auxiliary pointers for swapping */
    186:   PetscInt *ihlp1;                /* Pointers to new version of arrays, */
    187:   PetscInt *ihlp2;                /* Pointers to previous version of arrays, */

    189:   PetscFunctionBegin;
    190:   PetscCall(PetscMalloc1(nrows, &ialloc));

    192:   ihlp1 = ialloc;
    193:   ihlp2 = isort;

    195:   /* Sorted array chunks are first 1 long, and increase until they are the complete array */
    196:   for (istep = 1; istep < nrows; istep *= 2) {
    197:     /*
    198:       Combine sorted parts
    199:           istart:istart+istep-1 and istart+istep-1:istart+2*istep-1
    200:       of ihlp2 and vhlp2

    202:       into one sorted part
    203:           istart:istart+2*istep-1
    204:       of ihlp1 and vhlp1
    205:     */
    206:     for (istart = 0; istart < nrows; istart += 2 * istep) {
    207:       /* Set counters and bound array part endings */
    208:       i1    = istart;
    209:       i1end = i1 + istep;
    210:       if (i1end > nrows) i1end = nrows;
    211:       i2    = istart + istep;
    212:       i2end = i2 + istep;
    213:       if (i2end > nrows) i2end = nrows;

    215:       /* Merge the two array parts */
    216:       for (i = istart; i < i2end; i++) {
    217:         if (i1 < i1end && i2 < i2end && spbas_row_order_icol(ihlp2[i1], ihlp2[i2], irow_in, icol_in, col_idx_type) < 0) {
    218:           ihlp1[i] = ihlp2[i1];
    219:           i1++;
    220:         } else if (i2 < i2end) {
    221:           ihlp1[i] = ihlp2[i2];
    222:           i2++;
    223:         } else {
    224:           ihlp1[i] = ihlp2[i1];
    225:           i1++;
    226:         }
    227:       }
    228:     }

    230:     /* Swap the two array sets */
    231:     iswap = ihlp2;
    232:     ihlp2 = ihlp1;
    233:     ihlp1 = iswap;
    234:   }

    236:   /* Copy one more time in case the sorted arrays are the temporary ones */
    237:   if (ihlp2 != isort) {
    238:     for (i = 0; i < nrows; i++) isort[i] = ihlp2[i];
    239:   }
    240:   PetscCall(PetscFree(ialloc));
    241:   PetscFunctionReturn(PETSC_SUCCESS);
    242: }

    244: /*
    245:   spbas_compress_pattern:
    246:      calculate a compressed sparseness pattern for a sparseness pattern
    247:      given in compressed row storage. The compressed sparseness pattern may
    248:      require (much) less memory.
    249: */
    250: PetscErrorCode spbas_compress_pattern(PetscInt *irow_in, PetscInt *icol_in, PetscInt nrows, PetscInt ncols, PetscInt col_idx_type, spbas_matrix *B, PetscReal *mem_reduction)
    251: {
    252:   PetscInt        nnz      = irow_in[nrows];
    253:   size_t          mem_orig = (nrows + nnz) * sizeof(PetscInt);
    254:   size_t          mem_compressed;
    255:   PetscInt       *isort;
    256:   PetscInt       *icols;
    257:   PetscInt        row_nnz;
    258:   PetscInt       *ipoint;
    259:   PetscBool      *used;
    260:   PetscInt        ptr;
    261:   PetscInt        i, j;
    262:   const PetscBool no_values = PETSC_FALSE;

    264:   PetscFunctionBegin;
    265:   /* Allocate the structure of the new matrix */
    266:   B->nrows        = nrows;
    267:   B->ncols        = ncols;
    268:   B->nnz          = nnz;
    269:   B->col_idx_type = col_idx_type;
    270:   B->block_data   = PETSC_TRUE;

    272:   PetscCall(spbas_allocate_pattern(B, no_values));

    274:   /* When using an offset array, set it */
    275:   if (col_idx_type == SPBAS_OFFSET_ARRAY) {
    276:     for (i = 0; i < nrows; i++) B->icol0[i] = icol_in[irow_in[i]];
    277:   }

    279:   /* Allocate the ordering for the rows */
    280:   PetscCall(PetscMalloc1(nrows, &isort));
    281:   PetscCall(PetscMalloc1(nrows, &ipoint));
    282:   PetscCall(PetscCalloc1(nrows, &used));

    284:   for (i = 0; i < nrows; i++) {
    285:     B->row_nnz[i] = irow_in[i + 1] - irow_in[i];
    286:     isort[i]      = i;
    287:     ipoint[i]     = i;
    288:   }

    290:   /* Sort the rows so that identical columns will be next to each other */
    291:   PetscCall(spbas_mergesort_icols(nrows, irow_in, icol_in, col_idx_type, isort));
    292:   PetscCall(PetscInfo(NULL, "Rows have been sorted for patterns\n"));

    294:   /* Replace identical rows with the first one in the list */
    295:   for (i = 1; i < nrows; i++) {
    296:     if (spbas_row_order_icol(isort[i - 1], isort[i], irow_in, icol_in, col_idx_type) == 0) ipoint[isort[i]] = ipoint[isort[i - 1]];
    297:   }

    299:   /* Collect the rows which are used*/
    300:   for (i = 0; i < nrows; i++) used[ipoint[i]] = PETSC_TRUE;

    302:   /* Calculate needed memory */
    303:   B->n_alloc_icol = 0;
    304:   for (i = 0; i < nrows; i++) {
    305:     if (used[i]) B->n_alloc_icol += B->row_nnz[i];
    306:   }
    307:   PetscCall(PetscMalloc1(B->n_alloc_icol, &B->alloc_icol));

    309:   /* Fill in the diagonal offsets for the rows which store their own data */
    310:   ptr = 0;
    311:   for (i = 0; i < B->nrows; i++) {
    312:     if (used[i]) {
    313:       B->icols[i] = &B->alloc_icol[ptr];
    314:       icols       = &icol_in[irow_in[i]];
    315:       row_nnz     = B->row_nnz[i];
    316:       if (col_idx_type == SPBAS_COLUMN_NUMBERS) {
    317:         for (j = 0; j < row_nnz; j++) B->icols[i][j] = icols[j];
    318:       } else if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) {
    319:         for (j = 0; j < row_nnz; j++) B->icols[i][j] = icols[j] - i;
    320:       } else if (col_idx_type == SPBAS_OFFSET_ARRAY) {
    321:         for (j = 0; j < row_nnz; j++) B->icols[i][j] = icols[j] - icols[0];
    322:       }
    323:       ptr += B->row_nnz[i];
    324:     }
    325:   }

    327:   /* Point to the right places for all data */
    328:   for (i = 0; i < nrows; i++) B->icols[i] = B->icols[ipoint[i]];
    329:   PetscCall(PetscInfo(NULL, "Row patterns have been compressed\n"));
    330:   PetscCall(PetscInfo(NULL, "         (%g nonzeros per row)\n", (double)((PetscReal)nnz / (PetscReal)nrows)));

    332:   PetscCall(PetscFree(isort));
    333:   PetscCall(PetscFree(used));
    334:   PetscCall(PetscFree(ipoint));

    336:   mem_compressed = spbas_memory_requirement(*B);
    337:   *mem_reduction = 100.0 * (PetscReal)(mem_orig - mem_compressed) / (PetscReal)mem_orig;
    338:   PetscFunctionReturn(PETSC_SUCCESS);
    339: }

    341: /*
    342:    spbas_incomplete_cholesky
    343:        Incomplete Cholesky decomposition
    344: */
    345: #include <../src/mat/impls/aij/seq/bas/spbas_cholesky.h>

    347: /*
    348:   spbas_delete : de-allocate the arrays owned by this matrix
    349: */
    350: PetscErrorCode spbas_delete(spbas_matrix matrix)
    351: {
    352:   PetscInt i;

    354:   PetscFunctionBegin;
    355:   if (matrix.block_data) {
    356:     PetscCall(PetscFree(matrix.alloc_icol));
    357:     if (matrix.values) PetscCall(PetscFree(matrix.alloc_val));
    358:   } else {
    359:     for (i = 0; i < matrix.nrows; i++) PetscCall(PetscFree(matrix.icols[i]));
    360:     PetscCall(PetscFree(matrix.icols));
    361:     if (matrix.values) {
    362:       for (i = 0; i < matrix.nrows; i++) PetscCall(PetscFree(matrix.values[i]));
    363:     }
    364:   }

    366:   PetscCall(PetscFree(matrix.row_nnz));
    367:   PetscCall(PetscFree(matrix.icols));
    368:   if (matrix.col_idx_type == SPBAS_OFFSET_ARRAY) PetscCall(PetscFree(matrix.icol0));
    369:   PetscCall(PetscFree(matrix.values));
    370:   PetscFunctionReturn(PETSC_SUCCESS);
    371: }

    373: /*
    374: spbas_matrix_to_crs:
    375:    Convert an spbas_matrix to compessed row storage
    376: */
    377: PetscErrorCode spbas_matrix_to_crs(spbas_matrix matrix_A, MatScalar **val_out, PetscInt **irow_out, PetscInt **icol_out)
    378: {
    379:   PetscInt     nrows = matrix_A.nrows;
    380:   PetscInt     nnz   = matrix_A.nnz;
    381:   PetscInt     i, j, r_nnz, i0;
    382:   PetscInt    *irow;
    383:   PetscInt    *icol;
    384:   PetscInt    *icol_A;
    385:   MatScalar   *val;
    386:   PetscScalar *val_A;
    387:   PetscInt     col_idx_type = matrix_A.col_idx_type;
    388:   PetscBool    do_values    = matrix_A.values ? PETSC_TRUE : PETSC_FALSE;

    390:   PetscFunctionBegin;
    391:   PetscCall(PetscMalloc1(nrows + 1, &irow));
    392:   PetscCall(PetscMalloc1(nnz, &icol));
    393:   *icol_out = icol;
    394:   *irow_out = irow;
    395:   if (do_values) {
    396:     PetscCall(PetscMalloc1(nnz, &val));
    397:     *val_out  = val;
    398:     *icol_out = icol;
    399:     *irow_out = irow;
    400:   }

    402:   irow[0] = 0;
    403:   for (i = 0; i < nrows; i++) {
    404:     r_nnz       = matrix_A.row_nnz[i];
    405:     i0          = irow[i];
    406:     irow[i + 1] = i0 + r_nnz;
    407:     icol_A      = matrix_A.icols[i];

    409:     if (do_values) {
    410:       val_A = matrix_A.values[i];
    411:       for (j = 0; j < r_nnz; j++) {
    412:         icol[i0 + j] = icol_A[j];
    413:         val[i0 + j]  = val_A[j];
    414:       }
    415:     } else {
    416:       for (j = 0; j < r_nnz; j++) icol[i0 + j] = icol_A[j];
    417:     }

    419:     if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) {
    420:       for (j = 0; j < r_nnz; j++) icol[i0 + j] += i;
    421:     } else if (col_idx_type == SPBAS_OFFSET_ARRAY) {
    422:       i0 = matrix_A.icol0[i];
    423:       for (j = 0; j < r_nnz; j++) icol[i0 + j] += i0;
    424:     }
    425:   }
    426:   PetscFunctionReturn(PETSC_SUCCESS);
    427: }

    429: /*
    430:     spbas_transpose
    431:        return the transpose of a matrix
    432: */
    433: PetscErrorCode spbas_transpose(spbas_matrix in_matrix, spbas_matrix *result)
    434: {
    435:   PetscInt     col_idx_type = in_matrix.col_idx_type;
    436:   PetscInt     nnz          = in_matrix.nnz;
    437:   PetscInt     ncols        = in_matrix.nrows;
    438:   PetscInt     nrows        = in_matrix.ncols;
    439:   PetscInt     i, j, k;
    440:   PetscInt     r_nnz;
    441:   PetscInt    *irow;
    442:   PetscInt     icol0 = 0;
    443:   PetscScalar *val;

    445:   PetscFunctionBegin;
    446:   /* Copy input values */
    447:   result->nrows        = nrows;
    448:   result->ncols        = ncols;
    449:   result->nnz          = nnz;
    450:   result->col_idx_type = SPBAS_COLUMN_NUMBERS;
    451:   result->block_data   = PETSC_TRUE;

    453:   /* Allocate sparseness pattern */
    454:   PetscCall(spbas_allocate_pattern(result, in_matrix.values ? PETSC_TRUE : PETSC_FALSE));

    456:   /*  Count the number of nonzeros in each row */
    457:   for (i = 0; i < nrows; i++) result->row_nnz[i] = 0;

    459:   for (i = 0; i < ncols; i++) {
    460:     r_nnz = in_matrix.row_nnz[i];
    461:     irow  = in_matrix.icols[i];
    462:     if (col_idx_type == SPBAS_COLUMN_NUMBERS) {
    463:       for (j = 0; j < r_nnz; j++) result->row_nnz[irow[j]]++;
    464:     } else if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) {
    465:       for (j = 0; j < r_nnz; j++) result->row_nnz[i + irow[j]]++;
    466:     } else if (col_idx_type == SPBAS_OFFSET_ARRAY) {
    467:       icol0 = in_matrix.icol0[i];
    468:       for (j = 0; j < r_nnz; j++) result->row_nnz[icol0 + irow[j]]++;
    469:     }
    470:   }

    472:   /* Set the pointers to the data */
    473:   PetscCall(spbas_allocate_data(result));

    475:   /* Reset the number of nonzeros in each row */
    476:   for (i = 0; i < nrows; i++) result->row_nnz[i] = 0;

    478:   /* Fill the data arrays */
    479:   if (in_matrix.values) {
    480:     for (i = 0; i < ncols; i++) {
    481:       r_nnz = in_matrix.row_nnz[i];
    482:       irow  = in_matrix.icols[i];
    483:       val   = in_matrix.values[i];

    485:       if (col_idx_type == SPBAS_COLUMN_NUMBERS) icol0 = 0;
    486:       else if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) icol0 = i;
    487:       else if (col_idx_type == SPBAS_OFFSET_ARRAY) icol0 = in_matrix.icol0[i];
    488:       for (j = 0; j < r_nnz; j++) {
    489:         k                                     = icol0 + irow[j];
    490:         result->icols[k][result->row_nnz[k]]  = i;
    491:         result->values[k][result->row_nnz[k]] = val[j];
    492:         result->row_nnz[k]++;
    493:       }
    494:     }
    495:   } else {
    496:     for (i = 0; i < ncols; i++) {
    497:       r_nnz = in_matrix.row_nnz[i];
    498:       irow  = in_matrix.icols[i];

    500:       if (col_idx_type == SPBAS_COLUMN_NUMBERS) icol0 = 0;
    501:       else if (col_idx_type == SPBAS_DIAGONAL_OFFSETS) icol0 = i;
    502:       else if (col_idx_type == SPBAS_OFFSET_ARRAY) icol0 = in_matrix.icol0[i];

    504:       for (j = 0; j < r_nnz; j++) {
    505:         k                                    = icol0 + irow[j];
    506:         result->icols[k][result->row_nnz[k]] = i;
    507:         result->row_nnz[k]++;
    508:       }
    509:     }
    510:   }
    511:   PetscFunctionReturn(PETSC_SUCCESS);
    512: }

    514: /*
    515:    spbas_mergesort

    517:       mergesort for an array of integers and an array of associated
    518:       reals

    520:       on output, icol[0..nnz-1] is increasing;
    521:                   val[0..nnz-1] has undergone the same permutation as icol

    523:       NB: val may be NULL: in that case, only the integers are sorted

    525: */
    526: static PetscErrorCode spbas_mergesort(PetscInt nnz, PetscInt *icol, PetscScalar *val)
    527: {
    528:   PetscInt     istep;                /* Chunk-sizes of already sorted parts of arrays */
    529:   PetscInt     i, i1, i2;            /* Loop counters for (partly) sorted arrays */
    530:   PetscInt     istart, i1end, i2end; /* start of newly sorted array part, end of both parts */
    531:   PetscInt    *ialloc;               /* Allocated arrays */
    532:   PetscScalar *valloc = NULL;
    533:   PetscInt    *iswap; /* auxiliary pointers for swapping */
    534:   PetscScalar *vswap;
    535:   PetscInt    *ihlp1;        /* Pointers to new version of arrays, */
    536:   PetscScalar *vhlp1 = NULL; /* (arrays under construction) */
    537:   PetscInt    *ihlp2;        /* Pointers to previous version of arrays, */
    538:   PetscScalar *vhlp2 = NULL;

    540:   PetscFunctionBegin;
    541:   PetscCall(PetscMalloc1(nnz, &ialloc));
    542:   ihlp1 = ialloc;
    543:   ihlp2 = icol;

    545:   if (val) {
    546:     PetscCall(PetscMalloc1(nnz, &valloc));
    547:     vhlp1 = valloc;
    548:     vhlp2 = val;
    549:   }

    551:   /* Sorted array chunks are first 1 long, and increase until they are the complete array */
    552:   for (istep = 1; istep < nnz; istep *= 2) {
    553:     /*
    554:       Combine sorted parts
    555:           istart:istart+istep-1 and istart+istep-1:istart+2*istep-1
    556:       of ihlp2 and vhlp2

    558:       into one sorted part
    559:           istart:istart+2*istep-1
    560:       of ihlp1 and vhlp1
    561:     */
    562:     for (istart = 0; istart < nnz; istart += 2 * istep) {
    563:       /* Set counters and bound array part endings */
    564:       i1    = istart;
    565:       i1end = i1 + istep;
    566:       if (i1end > nnz) i1end = nnz;
    567:       i2    = istart + istep;
    568:       i2end = i2 + istep;
    569:       if (i2end > nnz) i2end = nnz;

    571:       /* Merge the two array parts */
    572:       if (val) {
    573:         for (i = istart; i < i2end; i++) {
    574:           if (i1 < i1end && i2 < i2end && ihlp2[i1] < ihlp2[i2]) {
    575:             ihlp1[i] = ihlp2[i1];
    576:             vhlp1[i] = vhlp2[i1];
    577:             i1++;
    578:           } else if (i2 < i2end) {
    579:             ihlp1[i] = ihlp2[i2];
    580:             vhlp1[i] = vhlp2[i2];
    581:             i2++;
    582:           } else {
    583:             ihlp1[i] = ihlp2[i1];
    584:             vhlp1[i] = vhlp2[i1];
    585:             i1++;
    586:           }
    587:         }
    588:       } else {
    589:         for (i = istart; i < i2end; i++) {
    590:           if (i1 < i1end && i2 < i2end && ihlp2[i1] < ihlp2[i2]) {
    591:             ihlp1[i] = ihlp2[i1];
    592:             i1++;
    593:           } else if (i2 < i2end) {
    594:             ihlp1[i] = ihlp2[i2];
    595:             i2++;
    596:           } else {
    597:             ihlp1[i] = ihlp2[i1];
    598:             i1++;
    599:           }
    600:         }
    601:       }
    602:     }

    604:     /* Swap the two array sets */
    605:     iswap = ihlp2;
    606:     ihlp2 = ihlp1;
    607:     ihlp1 = iswap;
    608:     vswap = vhlp2;
    609:     vhlp2 = vhlp1;
    610:     vhlp1 = vswap;
    611:   }

    613:   /* Copy one more time in case the sorted arrays are the temporary ones */
    614:   if (ihlp2 != icol) {
    615:     for (i = 0; i < nnz; i++) icol[i] = ihlp2[i];
    616:     if (val) {
    617:       for (i = 0; i < nnz; i++) val[i] = vhlp2[i];
    618:     }
    619:   }

    621:   PetscCall(PetscFree(ialloc));
    622:   if (val) PetscCall(PetscFree(valloc));
    623:   PetscFunctionReturn(PETSC_SUCCESS);
    624: }

    626: /*
    627:   spbas_apply_reordering_rows:
    628:     apply the given reordering to the rows:  matrix_A = matrix_A(perm,:);
    629: */
    630: static PetscErrorCode spbas_apply_reordering_rows(spbas_matrix *matrix_A, const PetscInt *permutation)
    631: {
    632:   PetscInt      i, j, ip;
    633:   PetscInt      nrows = matrix_A->nrows;
    634:   PetscInt     *row_nnz;
    635:   PetscInt    **icols;
    636:   PetscBool     do_values = matrix_A->values ? PETSC_TRUE : PETSC_FALSE;
    637:   PetscScalar **vals      = NULL;

    639:   PetscFunctionBegin;
    640:   PetscCheck(matrix_A->col_idx_type == SPBAS_DIAGONAL_OFFSETS, PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "must have diagonal offsets in pattern");

    642:   if (do_values) PetscCall(PetscMalloc1(nrows, &vals));
    643:   PetscCall(PetscMalloc1(nrows, &row_nnz));
    644:   PetscCall(PetscMalloc1(nrows, &icols));

    646:   for (i = 0; i < nrows; i++) {
    647:     ip = permutation[i];
    648:     if (do_values) vals[i] = matrix_A->values[ip];
    649:     icols[i]   = matrix_A->icols[ip];
    650:     row_nnz[i] = matrix_A->row_nnz[ip];
    651:     for (j = 0; j < row_nnz[i]; j++) icols[i][j] += ip - i;
    652:   }

    654:   if (do_values) PetscCall(PetscFree(matrix_A->values));
    655:   PetscCall(PetscFree(matrix_A->icols));
    656:   PetscCall(PetscFree(matrix_A->row_nnz));

    658:   if (do_values) matrix_A->values = vals;
    659:   matrix_A->icols   = icols;
    660:   matrix_A->row_nnz = row_nnz;
    661:   PetscFunctionReturn(PETSC_SUCCESS);
    662: }

    664: /*
    665:   spbas_apply_reordering_cols:
    666:     apply the given reordering to the columns:  matrix_A(:,perm) = matrix_A;
    667: */
    668: static PetscErrorCode spbas_apply_reordering_cols(spbas_matrix *matrix_A, const PetscInt *permutation)
    669: {
    670:   PetscInt     i, j;
    671:   PetscInt     nrows = matrix_A->nrows;
    672:   PetscInt     row_nnz;
    673:   PetscInt    *icols;
    674:   PetscBool    do_values = matrix_A->values ? PETSC_TRUE : PETSC_FALSE;
    675:   PetscScalar *vals      = NULL;

    677:   PetscFunctionBegin;
    678:   PetscCheck(matrix_A->col_idx_type == SPBAS_DIAGONAL_OFFSETS, PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "must have diagonal offsets in pattern");

    680:   for (i = 0; i < nrows; i++) {
    681:     icols   = matrix_A->icols[i];
    682:     row_nnz = matrix_A->row_nnz[i];
    683:     if (do_values) vals = matrix_A->values[i];

    685:     for (j = 0; j < row_nnz; j++) icols[j] = permutation[i + icols[j]] - i;
    686:     PetscCall(spbas_mergesort(row_nnz, icols, vals));
    687:   }
    688:   PetscFunctionReturn(PETSC_SUCCESS);
    689: }

    691: /*
    692:   spbas_apply_reordering:
    693:     apply the given reordering:  matrix_A(perm,perm) = matrix_A;
    694: */
    695: PetscErrorCode spbas_apply_reordering(spbas_matrix *matrix_A, const PetscInt *permutation, const PetscInt *inv_perm)
    696: {
    697:   PetscFunctionBegin;
    698:   PetscCall(spbas_apply_reordering_rows(matrix_A, inv_perm));
    699:   PetscCall(spbas_apply_reordering_cols(matrix_A, permutation));
    700:   PetscFunctionReturn(PETSC_SUCCESS);
    701: }

    703: PetscErrorCode spbas_pattern_only(PetscInt nrows, PetscInt ncols, PetscInt *ai, PetscInt *aj, spbas_matrix *result)
    704: {
    705:   spbas_matrix retval;
    706:   PetscInt     i, j, i0, r_nnz;

    708:   PetscFunctionBegin;
    709:   /* Copy input values */
    710:   retval.nrows = nrows;
    711:   retval.ncols = ncols;
    712:   retval.nnz   = ai[nrows];

    714:   retval.block_data   = PETSC_TRUE;
    715:   retval.col_idx_type = SPBAS_DIAGONAL_OFFSETS;

    717:   /* Allocate output matrix */
    718:   PetscCall(spbas_allocate_pattern(&retval, PETSC_FALSE));
    719:   for (i = 0; i < nrows; i++) retval.row_nnz[i] = ai[i + 1] - ai[i];
    720:   PetscCall(spbas_allocate_data(&retval));
    721:   /* Copy the structure */
    722:   for (i = 0; i < retval.nrows; i++) {
    723:     i0    = ai[i];
    724:     r_nnz = ai[i + 1] - i0;

    726:     for (j = 0; j < r_nnz; j++) retval.icols[i][j] = aj[i0 + j] - i;
    727:   }
    728:   *result = retval;
    729:   PetscFunctionReturn(PETSC_SUCCESS);
    730: }

    732: /*
    733:    spbas_mark_row_power:
    734:       Mark the columns in row 'row' which are nonzero in
    735:           matrix^2log(marker).
    736: */
    737: static PetscErrorCode spbas_mark_row_power(PetscInt     *iwork,     /* marker-vector */
    738:                                            PetscInt      row,       /* row for which the columns are marked */
    739:                                            spbas_matrix *in_matrix, /* matrix for which the power is being  calculated */
    740:                                            PetscInt      marker,    /* marker-value: 2^power */
    741:                                            PetscInt      minmrk,    /* lower bound for marked points */
    742:                                            PetscInt      maxmrk)         /* upper bound for marked points */
    743: {
    744:   PetscInt i, j, nnz;

    746:   PetscFunctionBegin;
    747:   nnz = in_matrix->row_nnz[row];

    749:   /* For higher powers, call this function recursively */
    750:   if (marker > 1) {
    751:     for (i = 0; i < nnz; i++) {
    752:       j = row + in_matrix->icols[row][i];
    753:       if (minmrk <= j && j < maxmrk && iwork[j] < marker) {
    754:         PetscCall(spbas_mark_row_power(iwork, row + in_matrix->icols[row][i], in_matrix, marker / 2, minmrk, maxmrk));
    755:         iwork[j] |= marker;
    756:       }
    757:     }
    758:   } else {
    759:     /*  Mark the columns reached */
    760:     for (i = 0; i < nnz; i++) {
    761:       j = row + in_matrix->icols[row][i];
    762:       if (minmrk <= j && j < maxmrk) iwork[j] |= 1;
    763:     }
    764:   }
    765:   PetscFunctionReturn(PETSC_SUCCESS);
    766: }

    768: /*
    769:    spbas_power
    770:       Calculate sparseness patterns for incomplete Cholesky decompositions
    771:       of a given order: (almost) all nonzeros of the matrix^(order+1) which
    772:       are inside the band width are found and stored in the output sparseness
    773:       pattern.
    774: */
    775: PetscErrorCode spbas_power(spbas_matrix in_matrix, PetscInt power, spbas_matrix *result)
    776: {
    777:   spbas_matrix retval;
    778:   PetscInt     nrows = in_matrix.nrows;
    779:   PetscInt     ncols = in_matrix.ncols;
    780:   PetscInt     i, j, kend;
    781:   PetscInt     nnz, inz;
    782:   PetscInt    *iwork;
    783:   PetscInt     marker;
    784:   PetscInt     maxmrk = 0;

    786:   PetscFunctionBegin;
    787:   PetscCheck(in_matrix.col_idx_type == SPBAS_DIAGONAL_OFFSETS, PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "must have diagonal offsets in pattern");
    788:   PetscCheck(ncols == nrows, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "Dimension error");
    789:   PetscCheck(!in_matrix.values, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "Input array must be sparseness pattern (no values)");
    790:   PetscCheck(power > 0, PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "Power must be 1 or up");

    792:   /* Copy input values*/
    793:   retval.nrows        = ncols;
    794:   retval.ncols        = nrows;
    795:   retval.nnz          = 0;
    796:   retval.col_idx_type = SPBAS_DIAGONAL_OFFSETS;
    797:   retval.block_data   = PETSC_FALSE;

    799:   /* Allocate sparseness pattern */
    800:   PetscCall(spbas_allocate_pattern(&retval, in_matrix.values ? PETSC_TRUE : PETSC_FALSE));

    802:   /* Allocate marker array: note sure the max needed so use the max of the two */
    803:   PetscCall(PetscCalloc1(PetscMax(ncols, nrows), &iwork));

    805:   /* Calculate marker values */
    806:   marker = 1;
    807:   for (i = 1; i < power; i++) marker *= 2;

    809:   for (i = 0; i < nrows; i++) {
    810:     /* Calculate the pattern for each row */

    812:     nnz  = in_matrix.row_nnz[i];
    813:     kend = i + in_matrix.icols[i][nnz - 1];
    814:     if (maxmrk <= kend) maxmrk = kend + 1;
    815:     PetscCall(spbas_mark_row_power(iwork, i, &in_matrix, marker, i, maxmrk));

    817:     /* Count the columns*/
    818:     nnz = 0;
    819:     for (j = i; j < maxmrk; j++) nnz += (iwork[j] != 0);

    821:     /* Allocate the column indices */
    822:     retval.row_nnz[i] = nnz;
    823:     PetscCall(PetscMalloc1(nnz, &retval.icols[i]));

    825:     /* Administrate the column indices */
    826:     inz = 0;
    827:     for (j = i; j < maxmrk; j++) {
    828:       if (iwork[j]) {
    829:         retval.icols[i][inz] = j - i;
    830:         inz++;
    831:         iwork[j] = 0;
    832:       }
    833:     }
    834:     retval.nnz += nnz;
    835:   }
    836:   PetscCall(PetscFree(iwork));
    837:   *result = retval;
    838:   PetscFunctionReturn(PETSC_SUCCESS);
    839: }

    841: /*
    842:    spbas_keep_upper:
    843:       remove the lower part of the matrix: keep the upper part
    844: */
    845: PetscErrorCode spbas_keep_upper(spbas_matrix *inout_matrix)
    846: {
    847:   PetscInt i, j;
    848:   PetscInt jstart;

    850:   PetscFunctionBegin;
    851:   PetscCheck(!inout_matrix->block_data, PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "Not yet for block data matrices");
    852:   for (i = 0; i < inout_matrix->nrows; i++) {
    853:     for (jstart = 0; (jstart < inout_matrix->row_nnz[i]) && (inout_matrix->icols[i][jstart] < 0); jstart++) { }
    854:     if (jstart > 0) {
    855:       for (j = 0; j < inout_matrix->row_nnz[i] - jstart; j++) inout_matrix->icols[i][j] = inout_matrix->icols[i][j + jstart];

    857:       if (inout_matrix->values) {
    858:         for (j = 0; j < inout_matrix->row_nnz[i] - jstart; j++) inout_matrix->values[i][j] = inout_matrix->values[i][j + jstart];
    859:       }

    861:       inout_matrix->row_nnz[i] -= jstart;

    863:       inout_matrix->icols[i] = (PetscInt *)realloc((void *)inout_matrix->icols[i], inout_matrix->row_nnz[i] * sizeof(PetscInt));

    865:       if (inout_matrix->values) inout_matrix->values[i] = (PetscScalar *)realloc((void *)inout_matrix->values[i], inout_matrix->row_nnz[i] * sizeof(PetscScalar));
    866:       inout_matrix->nnz -= jstart;
    867:     }
    868:   }
    869:   PetscFunctionReturn(PETSC_SUCCESS);
    870: }