Date: 2016-07-24T16:52:44+00:00

Actual source code: ij.c
petsc-3.7.3 2016-07-24
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      2: #include <../src/mat/impls/aij/seq/aij.h>

      6: /*
      7:   MatToSymmetricIJ_SeqAIJ - Convert a (generally nonsymmetric) sparse AIJ matrix
      8:            to IJ format (ignore the "A" part) Allocates the space needed. Uses only
      9:            the lower triangular part of the matrix.

     11:     Description:
     12:     Take the data in the row-oriented sparse storage and build the
     13:     IJ data for the Matrix.  Return 0 on success,row + 1 on failure
     14:     at that row. Produces the ij for a symmetric matrix by using
     15:     the lower triangular part of the matrix if lower_triangular is PETSC_TRUE;
     16:     it uses the upper triangular otherwise.

     18:     Input Parameters:
     19: .   Matrix - matrix to convert
     20: .   lower_triangular - symmetrize the lower triangular part
     21: .   shiftin - the shift for the original matrix (0 or 1)
     22: .   shiftout - the shift required for the ordering routine (0 or 1)

     24:     Output Parameters:
     25: .   ia     - ia part of IJ representation (row information)
     26: .   ja     - ja part (column indices)

     28:     Notes:
     29:     Both ia and ja may be freed with PetscFree();
     30:     This routine is provided for ordering routines that require a
     31:     symmetric structure.  It is required since those routines call
     32:     SparsePak routines that expect a symmetric  matrix.
     33: */
     34: PetscErrorCode MatToSymmetricIJ_SeqAIJ(PetscInt m,PetscInt *ai,PetscInt *aj,PetscBool lower_triangular,PetscInt shiftin,PetscInt shiftout,PetscInt **iia,PetscInt **jja)
     35: {
     37:   PetscInt       *work,*ia,*ja,*j,i,nz,row,col;

     40:   /* allocate space for row pointers */
     41:   PetscMalloc1(m+1,&ia);
     42:   *iia = ia;
     43:   PetscMemzero(ia,(m+1)*sizeof(PetscInt));
     44:   PetscMalloc1(m+1,&work);

     46:   /* determine the number of columns in each row */
     47:   ia[0] = shiftout;
     48:   for (row = 0; row < m; row++) {
     49:     nz = ai[row+1] - ai[row];
     50:     j  = aj + ai[row] + shiftin;
     51:     while (nz--) {
     52:       col = *j++ + shiftin;
     53:       if (lower_triangular) {
     54:         if (col > row) break;
     55:       } else {
     56:         if (col < row) break;
     57:       }
     58:       if (col != row) ia[row+1]++;
     59:       ia[col+1]++;
     60:     }
     61:   }

     63:   /* shiftin ia[i] to point to next row */
     64:   for (i=1; i<m+1; i++) {
     65:     row       = ia[i-1];
     66:     ia[i]    += row;
     67:     work[i-1] = row - shiftout;
     68:   }

     70:   /* allocate space for column pointers */
     71:   nz   = ia[m] + (!shiftin);
     72:   PetscMalloc1(nz,&ja);
     73:   *jja = ja;

     75:   /* loop over lower triangular part putting into ja */
     76:   for (row = 0; row < m; row++) {
     77:     nz = ai[row+1] - ai[row];
     78:     j  = aj + ai[row] + shiftin;
     79:     while (nz--) {
     80:       col = *j++ + shiftin;
     81:       if (lower_triangular) {
     82:         if (col > row) break;
     83:       } else {
     84:         if (col < row) break;
     85:       }
     86:       if (col != row) ja[work[col]++] = row + shiftout;
     87:       ja[work[row]++] = col + shiftout;
     88:     }
     89:   }
     90:   PetscFree(work);
     91:   return(0);
     92: }