1 #include <petsc/private/matimpl.h> /*I "petscmat.h" I*/ 2 3 /*@C 4 MatCheckCompressedRow - Determines whether the compressed row matrix format should be used. 5 If the format is to be used, this routine creates Mat_CompressedRow struct. 6 Compressed row format provides high performance routines by taking advantage of zero rows. 7 Supported types are MATAIJ, MATBAIJ and MATSBAIJ. 8 9 Collective 10 11 Input Parameters: 12 + A - the matrix 13 . nrows - number of rows with nonzero entries 14 . compressedrow - pointer to the struct Mat_CompressedRow 15 . ai - row pointer used by seqaij and seqbaij 16 . mbs - number of (block) rows represented by ai 17 - ratio - ratio of (num of zero rows)/m, used to determine if the compressed row format should be used 18 19 Developer Note: The reason this takes the compressedrow, ai and mbs arguments is because it is called by both the SeqAIJ and SEQBAIJ matrices and 20 the values are not therefore obtained by directly taking the values from the matrix object. 21 This is not a general public routine and hence is not listed in petscmat.h (it exposes a private data structure) but it is used 22 by some preconditioners and hence is labeled as PETSC_EXTERN 23 24 Level: developer 25 @*/ 26 PETSC_EXTERN PetscErrorCode MatCheckCompressedRow(Mat A, PetscInt nrows, Mat_CompressedRow *compressedrow, PetscInt *ai, PetscInt mbs, PetscReal ratio) 27 { 28 PetscInt *cpi = NULL, *ridx = NULL, nz, i, row; 29 30 PetscFunctionBegin; 31 /* in case this is being reused, delete old space */ 32 PetscCall(PetscFree2(compressedrow->i, compressedrow->rindex)); 33 34 /* compute number of zero rows */ 35 nrows = mbs - nrows; 36 37 /* if a large number of zero rows is found, use compressedrow data structure */ 38 if (nrows < ratio * mbs) { 39 compressedrow->use = PETSC_FALSE; 40 41 PetscCall(PetscInfo(A, "Found the ratio (num_zerorows %" PetscInt_FMT ")/(num_localrows %" PetscInt_FMT ") < %g. Do not use CompressedRow routines.\n", nrows, mbs, (double)ratio)); 42 } else { 43 compressedrow->use = PETSC_TRUE; 44 45 PetscCall(PetscInfo(A, "Found the ratio (num_zerorows %" PetscInt_FMT ")/(num_localrows %" PetscInt_FMT ") > %g. Use CompressedRow routines.\n", nrows, mbs, (double)ratio)); 46 47 /* set compressed row format */ 48 nrows = mbs - nrows; /* num of non-zero rows */ 49 PetscCall(PetscMalloc2(nrows + 1, &cpi, nrows, &ridx)); 50 row = 0; 51 cpi[0] = 0; 52 for (i = 0; i < mbs; i++) { 53 nz = ai[i + 1] - ai[i]; 54 if (nz == 0) continue; 55 cpi[row + 1] = ai[i + 1]; /* compressed row pointer */ 56 ridx[row++] = i; /* compressed row local index */ 57 } 58 compressedrow->nrows = nrows; 59 compressedrow->i = cpi; 60 compressedrow->rindex = ridx; 61 } 62 PetscFunctionReturn(PETSC_SUCCESS); 63 } 64