Date: 2026-05-01T06:11:56+00:00

Actual source code: baijsolvnat1.c

      1: #include <../src/mat/impls/baij/seq/baij.h>
      2: #include <petsc/private/kernels/blockinvert.h>

      4: /*
      5:       Special case where the matrix was ILU(0) factored in the natural
      6:    ordering. This eliminates the need for the column and row permutation.
      7: */
      8: PetscErrorCode MatSolve_SeqBAIJ_1_NaturalOrdering_inplace(Mat A, Vec bb, Vec xx)
      9: {
     10:   Mat_SeqBAIJ       *a = (Mat_SeqBAIJ *)A->data;
     11:   const PetscInt     n = a->mbs, *vi, *ai = a->i, *aj = a->j, *diag = a->diag;
     12:   const MatScalar   *aa = a->a, *v;
     13:   PetscScalar       *x;
     14:   const PetscScalar *b;
     15:   PetscScalar        s1, x1;
     16:   PetscInt           jdx, idt, idx, nz, i;

     18:   PetscFunctionBegin;
     19:   PetscCall(VecGetArrayRead(bb, &b));
     20:   PetscCall(VecGetArray(xx, &x));

     22:   /* forward solve the lower triangular */
     23:   idx  = 0;
     24:   x[0] = b[0];
     25:   for (i = 1; i < n; i++) {
     26:     v  = aa + ai[i];
     27:     vi = aj + ai[i];
     28:     nz = diag[i] - ai[i];
     29:     idx += 1;
     30:     s1 = b[idx];
     31:     while (nz--) {
     32:       jdx = *vi++;
     33:       x1  = x[jdx];
     34:       s1 -= v[0] * x1;
     35:       v += 1;
     36:     }
     37:     x[idx] = s1;
     38:   }
     39:   /* backward solve the upper triangular */
     40:   for (i = n - 1; i >= 0; i--) {
     41:     v   = aa + diag[i] + 1;
     42:     vi  = aj + diag[i] + 1;
     43:     nz  = ai[i + 1] - diag[i] - 1;
     44:     idt = i;
     45:     s1  = x[idt];
     46:     while (nz--) {
     47:       idx = *vi++;
     48:       x1  = x[idx];
     49:       s1 -= v[0] * x1;
     50:       v += 1;
     51:     }
     52:     v      = aa + diag[i];
     53:     x[idt] = v[0] * s1;
     54:   }
     55:   PetscCall(VecRestoreArrayRead(bb, &b));
     56:   PetscCall(VecRestoreArray(xx, &x));
     57:   PetscCall(PetscLogFlops(2.0 * (a->nz) - A->cmap->n));
     58:   PetscFunctionReturn(PETSC_SUCCESS);
     59: }

     61: PetscErrorCode MatForwardSolve_SeqBAIJ_1_NaturalOrdering(Mat A, Vec bb, Vec xx)
     62: {
     63:   Mat_SeqBAIJ       *a = (Mat_SeqBAIJ *)A->data;
     64:   const PetscInt     n = a->mbs, *ai = a->i, *aj = a->j, *vi;
     65:   PetscScalar       *x, sum;
     66:   const PetscScalar *b;
     67:   const MatScalar   *aa = a->a, *v;
     68:   PetscInt           i, nz;

     70:   PetscFunctionBegin;
     71:   if (!n) PetscFunctionReturn(PETSC_SUCCESS);

     73:   PetscCall(VecGetArrayRead(bb, &b));
     74:   PetscCall(VecGetArray(xx, &x));

     76:   /* forward solve the lower triangular */
     77:   x[0] = b[0];
     78:   v    = aa;
     79:   vi   = aj;
     80:   for (i = 1; i < n; i++) {
     81:     nz  = ai[i + 1] - ai[i];
     82:     sum = b[i];
     83:     PetscSparseDenseMinusDot(sum, x, v, vi, nz);
     84:     v += nz;
     85:     vi += nz;
     86:     x[i] = sum;
     87:   }
     88:   PetscCall(PetscLogFlops(a->nz - A->cmap->n));
     89:   PetscCall(VecRestoreArrayRead(bb, &b));
     90:   PetscCall(VecRestoreArray(xx, &x));
     91:   PetscFunctionReturn(PETSC_SUCCESS);
     92: }

     94: PetscErrorCode MatBackwardSolve_SeqBAIJ_1_NaturalOrdering(Mat A, Vec bb, Vec xx)
     95: {
     96:   Mat_SeqBAIJ       *a = (Mat_SeqBAIJ *)A->data;
     97:   const PetscInt     n = a->mbs, *aj = a->j, *adiag = a->diag, *vi;
     98:   PetscScalar       *x, sum;
     99:   const PetscScalar *b;
    100:   const MatScalar   *aa = a->a, *v;
    101:   PetscInt           i, nz;

    103:   PetscFunctionBegin;
    104:   if (!n) PetscFunctionReturn(PETSC_SUCCESS);

    106:   PetscCall(VecGetArrayRead(bb, &b));
    107:   PetscCall(VecGetArray(xx, &x));

    109:   /* backward solve the upper triangular */
    110:   for (i = n - 1; i >= 0; i--) {
    111:     v   = aa + adiag[i + 1] + 1;
    112:     vi  = aj + adiag[i + 1] + 1;
    113:     nz  = adiag[i] - adiag[i + 1] - 1;
    114:     sum = b[i];
    115:     PetscSparseDenseMinusDot(sum, x, v, vi, nz);
    116:     x[i] = sum * v[nz]; /* x[i]=aa[adiag[i]]*sum; v++; */
    117:   }

    119:   PetscCall(PetscLogFlops(2.0 * a->nz - A->cmap->n));
    120:   PetscCall(VecRestoreArrayRead(bb, &b));
    121:   PetscCall(VecRestoreArray(xx, &x));
    122:   PetscFunctionReturn(PETSC_SUCCESS);
    123: }

    125: PetscErrorCode MatSolve_SeqBAIJ_1_NaturalOrdering(Mat A, Vec bb, Vec xx)
    126: {
    127:   Mat_SeqBAIJ       *a = (Mat_SeqBAIJ *)A->data;
    128:   const PetscInt     n = a->mbs, *ai = a->i, *aj = a->j, *adiag = a->diag, *vi;
    129:   PetscScalar       *x, sum;
    130:   const PetscScalar *b;
    131:   const MatScalar   *aa = a->a, *v;
    132:   PetscInt           i, nz;

    134:   PetscFunctionBegin;
    135:   if (!n) PetscFunctionReturn(PETSC_SUCCESS);

    137:   PetscCall(VecGetArrayRead(bb, &b));
    138:   PetscCall(VecGetArray(xx, &x));

    140:   /* forward solve the lower triangular */
    141:   x[0] = b[0];
    142:   v    = aa;
    143:   vi   = aj;
    144:   for (i = 1; i < n; i++) {
    145:     nz  = ai[i + 1] - ai[i];
    146:     sum = b[i];
    147:     PetscSparseDenseMinusDot(sum, x, v, vi, nz);
    148:     v += nz;
    149:     vi += nz;
    150:     x[i] = sum;
    151:   }

    153:   /* backward solve the upper triangular */
    154:   for (i = n - 1; i >= 0; i--) {
    155:     v   = aa + adiag[i + 1] + 1;
    156:     vi  = aj + adiag[i + 1] + 1;
    157:     nz  = adiag[i] - adiag[i + 1] - 1;
    158:     sum = x[i];
    159:     PetscSparseDenseMinusDot(sum, x, v, vi, nz);
    160:     x[i] = sum * v[nz]; /* x[i]=aa[adiag[i]]*sum; v++; */
    161:   }

    163:   PetscCall(PetscLogFlops(2.0 * a->nz - A->cmap->n));
    164:   PetscCall(VecRestoreArrayRead(bb, &b));
    165:   PetscCall(VecRestoreArray(xx, &x));
    166:   PetscFunctionReturn(PETSC_SUCCESS);
    167: }