Date: 2021-03-03T22:26:11+00:00

Actual source code: ij.c
petsc-3.14.5 2021-03-03
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      2: #include <../src/mat/impls/aij/seq/aij.h>

      4: /*
      5:   MatToSymmetricIJ_SeqAIJ - Convert a (generally nonsymmetric) sparse AIJ matrix
      6:            to IJ format (ignore the "A" part) Allocates the space needed. Uses only
      7:            the lower triangular part of the matrix.

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

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

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

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

     38:   /* allocate space for row pointers */
     39:   PetscCalloc1(m+1,&ia);
     40:   *iia = ia;
     41:   PetscMalloc1(m+1,&work);

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

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

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

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