1: #define PETSCMAT_DLL

 3:  #include include/private/matimpl.h

  7: /*@C
  8:    Mat_CheckCompressedRow - Determines whether the compressed row matrix format should be used. 
  9:       If the format is to be used, this routine creates Mat_CompressedRow struct.
 10:       Compressed row format provides high performance routines by taking advantage of zero rows.
 11:       Supported types are MATAIJ, MATBAIJ and MATSBAIJ.

 13:    Collective

 15:    Input Parameters:
 16: +  A             - the matrix
 17: .  compressedrow - pointer to the struct Mat_CompressedRow
 18: .  ai            - row pointer used by seqaij and seqbaij
 19: .  mbs           - number of (block) rows represented by ai
 20: -  ratio         - ratio of (num of zero rows)/m, used to determine if the compressed row format should be used

 22:    Level: developer
 23: @*/
 24: PetscErrorCode Mat_CheckCompressedRow(Mat A,Mat_CompressedRow *compressedrow,PetscInt *ai,PetscInt mbs,PetscReal ratio)
 25: {
 27:   PetscInt       nrows,*cpi=PETSC_NULL,*ridx=PETSC_NULL,nz,i,row;

 30:   if (!compressedrow->use) return(0);
 31:   if (compressedrow->checked){
 32:     if (!A->same_nonzero){
 33:       PetscFree(compressedrow->i);
 34:       compressedrow->rindex = PETSC_NULL;
 35:       PetscInfo(A,"Mat structure might be changed. Free memory and recheck.\n");
 36:     } else if (!compressedrow->i) {
 37:       /* Don't know why this occures. For safe, recheck. */
 38:       PetscInfo(A,"compressedrow.checked, but compressedrow.i==null. Recheck.\n");
 39:     } else { /* use compressedrow, checked, A->same_nonzero = PETSC_TRUE. Skip check */
 40:       PetscInfo7(A,"Skip check. m: %d, n: %d,M: %d, N: %d,nrows: %d, ii: %p, type: %s\n",A->rmap.n,A->cmap.n,A->rmap.N,A->cmap.N,compressedrow->nrows,compressedrow->i,A->type_name);
 41:       return(0);
 42:     }
 43:   }
 44:   compressedrow->checked = PETSC_TRUE;

 46:   /* compute number of zero rows */
 47:   nrows = 0;
 48:   for (i=0; i<mbs; i++){        /* for each row */
 49:     nz = ai[i+1] - ai[i];       /* number of nonzeros */
 50:     if (nz == 0) nrows++;
 51:   }
 52:   /* if a large number of zero rows is found, use compressedrow data structure */
 53:   if (nrows < ratio*mbs) {
 54:     compressedrow->use = PETSC_FALSE;
 55:     PetscInfo3(A,"Found the ratio (num_zerorows %d)/(num_localrows %d) < %G. Do not use CompressedRow routines.\n",nrows,mbs,ratio);
 56:   } else {
 57:     compressedrow->use = PETSC_TRUE;
 58:     PetscInfo3(A,"Found the ratio (num_zerorows %d)/(num_localrows %d) > %G. Use CompressedRow routines.\n",nrows,mbs,ratio);

 60:     /* set compressed row format */
 61:     nrows = mbs - nrows; /* num of non-zero rows */
 62:     PetscMalloc((2*nrows+1)*sizeof(PetscInt),&cpi);
 63:     ridx = cpi + nrows + 1;
 64:     row    = 0;
 65:     cpi[0] = 0;
 66:     for (i=0; i<mbs; i++){
 67:       nz = ai[i+1] - ai[i];
 68:       if (nz == 0) continue;
 69:       cpi[row+1]  = ai[i+1];    /* compressed row pointer */
 70:       ridx[row++] = i;          /* compressed row local index */
 71:     }
 72:     compressedrow->nrows  = nrows;
 73:     compressedrow->i      = cpi;
 74:     compressedrow->rindex = ridx;
 75:   }
 76: 
 77:   return(0);
 78: }