1af0996ceSBarry Smith #include <petsc/private/matimpl.h> /*I "petscmat.h" I*/ 226e093fcSHong Zhang 373e7a558SHong Zhang /*@C 4cd6b891eSBarry Smith MatCheckCompressedRow - Determines whether the compressed row matrix format should be used. 5f38b99b6SHong Zhang Compressed row format provides high performance routines by taking advantage of zero rows. 673e7a558SHong Zhang 773e7a558SHong Zhang Collective 873e7a558SHong Zhang 973e7a558SHong Zhang Input Parameters: 1073e7a558SHong Zhang + A - the matrix 1111e456e1SBarry Smith . nrows - number of rows with nonzero entries 1273e7a558SHong Zhang . compressedrow - pointer to the struct Mat_CompressedRow 132ef1f0ffSBarry Smith . ai - row pointer used by `MATSEQAIJ` and `MATSEQBAIJ` 142ef1f0ffSBarry Smith . mbs - number of (block) rows represented by `ai` 1573e7a558SHong Zhang - ratio - ratio of (num of zero rows)/m, used to determine if the compressed row format should be used 1673e7a558SHong Zhang 17*20f4b53cSBarry Smith Note: 18*20f4b53cSBarry Smith Supported types are `MATAIJ`, `MATBAIJ` and `MATSBAIJ`. 19*20f4b53cSBarry Smith 20*20f4b53cSBarry Smith Developer Note: 21*20f4b53cSBarry Smith The reason this takes the `compressedrow`, `ai` and `mbs` arguments is because it is called by both the `MATSEQAIJ` and `MATSEQBAIJ` matrices and 22340b11eeSBarry Smith the values are not therefore obtained by directly taking the values from the matrix object. 238aea9937SBarry Smith 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 248aea9937SBarry Smith by some preconditioners and hence is labeled as PETSC_EXTERN 258aea9937SBarry Smith 2673e7a558SHong Zhang Level: developer 27*20f4b53cSBarry Smith 28*20f4b53cSBarry Smith .seealso: `Mat`, `MATAIJ`, `MATBAIJ`, `MATSBAIJ`. 2973e7a558SHong Zhang @*/ 30d71ae5a4SJacob Faibussowitsch PETSC_EXTERN PetscErrorCode MatCheckCompressedRow(Mat A, PetscInt nrows, Mat_CompressedRow *compressedrow, PetscInt *ai, PetscInt mbs, PetscReal ratio) 31d71ae5a4SJacob Faibussowitsch { 3211e456e1SBarry Smith PetscInt *cpi = NULL, *ridx = NULL, nz, i, row; 3373e7a558SHong Zhang 3473e7a558SHong Zhang PetscFunctionBegin; 35cd6b891eSBarry Smith /* in case this is being reused, delete old space */ 369566063dSJacob Faibussowitsch PetscCall(PetscFree2(compressedrow->i, compressedrow->rindex)); 378865f1eaSKarl Rupp 3873e7a558SHong Zhang /* compute number of zero rows */ 3911e456e1SBarry Smith nrows = mbs - nrows; 40baa4e9faSMark F. Adams 41317fbc4cSHong Zhang /* if a large number of zero rows is found, use compressedrow data structure */ 42317fbc4cSHong Zhang if (nrows < ratio * mbs) { 4373e7a558SHong Zhang compressedrow->use = PETSC_FALSE; 448865f1eaSKarl Rupp 4563a3b9bcSJacob Faibussowitsch 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)); 4673e7a558SHong Zhang } else { 4773e7a558SHong Zhang compressedrow->use = PETSC_TRUE; 488865f1eaSKarl Rupp 4963a3b9bcSJacob Faibussowitsch PetscCall(PetscInfo(A, "Found the ratio (num_zerorows %" PetscInt_FMT ")/(num_localrows %" PetscInt_FMT ") > %g. Use CompressedRow routines.\n", nrows, mbs, (double)ratio)); 5073e7a558SHong Zhang 5173e7a558SHong Zhang /* set compressed row format */ 52317fbc4cSHong Zhang nrows = mbs - nrows; /* num of non-zero rows */ 539566063dSJacob Faibussowitsch PetscCall(PetscMalloc2(nrows + 1, &cpi, nrows, &ridx)); 5473e7a558SHong Zhang row = 0; 5573e7a558SHong Zhang cpi[0] = 0; 56317fbc4cSHong Zhang for (i = 0; i < mbs; i++) { 5773e7a558SHong Zhang nz = ai[i + 1] - ai[i]; 5873e7a558SHong Zhang if (nz == 0) continue; 5973e7a558SHong Zhang cpi[row + 1] = ai[i + 1]; /* compressed row pointer */ 607b2bb3b9SHong Zhang ridx[row++] = i; /* compressed row local index */ 6173e7a558SHong Zhang } 6273e7a558SHong Zhang compressedrow->nrows = nrows; 6373e7a558SHong Zhang compressedrow->i = cpi; 647b2bb3b9SHong Zhang compressedrow->rindex = ridx; 6573e7a558SHong Zhang } 663ba16761SJacob Faibussowitsch PetscFunctionReturn(PETSC_SUCCESS); 6773e7a558SHong Zhang } 68