1: #include <../src/mat/impls/aij/seq/aij.h>

  3: /*
  4:   MatToSymmetricIJ_SeqAIJ - Convert a (generally nonsymmetric) sparse AIJ matrix
  5:            to IJ format (ignore the "A" part) Allocates the space needed. Uses only
  6:            the lower triangular part of the matrix.

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

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

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

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

 35:   PetscFunctionBegin;
 36:   /* allocate space for row pointers */
 37:   PetscCall(PetscCalloc1(m + 1, &ia));
 38:   *iia = ia;
 39:   PetscCall(PetscMalloc1(m + 1, &work));

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

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

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

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