Actual source code: baijsolvtrannat1.c

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

  3: PetscErrorCode MatSolveTranspose_SeqBAIJ_1_NaturalOrdering(Mat A, Vec bb, Vec xx)
  4: {
  5:   Mat_SeqBAIJ       *a     = (Mat_SeqBAIJ *)A->data;
  6:   const PetscInt    *adiag = a->diag, *ai = a->i, *aj = a->j, *vi;
  7:   PetscInt           i, n = a->mbs, j;
  8:   PetscInt           nz;
  9:   PetscScalar       *x, *tmp, s1;
 10:   const MatScalar   *aa = a->a, *v;
 11:   const PetscScalar *b;

 13:   PetscFunctionBegin;
 14:   PetscCall(VecGetArrayRead(bb, &b));
 15:   PetscCall(VecGetArray(xx, &x));
 16:   tmp = a->solve_work;

 18:   /* copy the b into temp work space according to permutation */
 19:   for (i = 0; i < n; i++) tmp[i] = b[i];

 21:   /* forward solve the U^T */
 22:   for (i = 0; i < n; i++) {
 23:     v  = aa + adiag[i + 1] + 1;
 24:     vi = aj + adiag[i + 1] + 1;
 25:     nz = adiag[i] - adiag[i + 1] - 1;
 26:     s1 = tmp[i];
 27:     s1 *= v[nz]; /* multiply by inverse of diagonal entry */
 28:     for (j = 0; j < nz; j++) tmp[vi[j]] -= s1 * v[j];
 29:     tmp[i] = s1;
 30:   }

 32:   /* backward solve the L^T */
 33:   for (i = n - 1; i >= 0; i--) {
 34:     v  = aa + ai[i];
 35:     vi = aj + ai[i];
 36:     nz = ai[i + 1] - ai[i];
 37:     s1 = tmp[i];
 38:     for (j = 0; j < nz; j++) tmp[vi[j]] -= s1 * v[j];
 39:   }

 41:   /* copy tmp into x according to permutation */
 42:   for (i = 0; i < n; i++) x[i] = tmp[i];

 44:   PetscCall(VecRestoreArrayRead(bb, &b));
 45:   PetscCall(VecRestoreArray(xx, &x));

 47:   PetscCall(PetscLogFlops(2.0 * a->nz - A->cmap->n));
 48:   PetscFunctionReturn(PETSC_SUCCESS);
 49: }

 51: PetscErrorCode MatSolveTranspose_SeqBAIJ_1_NaturalOrdering_inplace(Mat A, Vec bb, Vec xx)
 52: {
 53:   Mat_SeqBAIJ     *a = (Mat_SeqBAIJ *)A->data;
 54:   PetscInt         i, nz;
 55:   const PetscInt  *diag = a->diag, n = a->mbs, *vi, *ai = a->i, *aj = a->j;
 56:   const MatScalar *aa = a->a, *v;
 57:   PetscScalar      s1, *x;

 59:   PetscFunctionBegin;
 60:   PetscCall(VecCopy(bb, xx));
 61:   PetscCall(VecGetArray(xx, &x));

 63:   /* forward solve the U^T */
 64:   for (i = 0; i < n; i++) {
 65:     v = aa + diag[i];
 66:     /* multiply by the inverse of the block diagonal */
 67:     s1 = (*v++) * x[i];
 68:     vi = aj + diag[i] + 1;
 69:     nz = ai[i + 1] - diag[i] - 1;
 70:     while (nz--) x[*vi++] -= (*v++) * s1;
 71:     x[i] = s1;
 72:   }
 73:   /* backward solve the L^T */
 74:   for (i = n - 1; i >= 0; i--) {
 75:     v  = aa + diag[i] - 1;
 76:     vi = aj + diag[i] - 1;
 77:     nz = diag[i] - ai[i];
 78:     s1 = x[i];
 79:     while (nz--) x[*vi--] -= (*v--) * s1;
 80:   }
 81:   PetscCall(VecRestoreArray(xx, &x));
 82:   PetscCall(PetscLogFlops(2.0 * (a->nz) - A->cmap->n));
 83:   PetscFunctionReturn(PETSC_SUCCESS);
 84: }