Actual source code: baijsolvtrannat1.c

petsc-3.11.3 2019-06-26
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```  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:   PetscErrorCode    ierr;
7:   const PetscInt    *adiag = a->diag,*ai = a->i,*aj = a->j,*vi;
8:   PetscInt          i,n = a->mbs,j;
9:   PetscInt          nz;
10:   PetscScalar       *x,*tmp,s1;
11:   const MatScalar   *aa = a->a,*v;
12:   const PetscScalar *b;

16:   VecGetArray(xx,&x);
17:   tmp  = a->solve_work;

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

23:   /* forward solve the U^T */
24:   for (i=0; i<n; i++) {
25:     v   = aa + adiag[i+1] + 1;
26:     vi  = aj + adiag[i+1] + 1;
28:     s1  = tmp[i];
29:     s1 *= v[nz];  /* multiply by inverse of diagonal entry */
30:     for (j=0; j<nz; j++) tmp[vi[j]] -= s1*v[j];
31:     tmp[i] = s1;
32:   }

34:   /* backward solve the L^T */
35:   for (i=n-1; i>=0; i--) {
36:     v  = aa + ai[i];
37:     vi = aj + ai[i];
38:     nz = ai[i+1] - ai[i];
39:     s1 = tmp[i];
40:     for (j=0; j<nz; j++) tmp[vi[j]] -= s1*v[j];
41:   }

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

47:   VecRestoreArray(xx,&x);

49:   PetscLogFlops(2.0*a->nz-A->cmap->n);
50:   return(0);
51: }

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

63:   VecCopy(bb,xx);
64:   VecGetArray(xx,&x);

66:   /* forward solve the U^T */
67:   for (i=0; i<n; i++) {

69:     v = aa + diag[i];
70:     /* multiply by the inverse of the block diagonal */
71:     s1 = (*v++)*x[i];
72:     vi = aj + diag[i] + 1;
73:     nz = ai[i+1] - diag[i] - 1;
74:     while (nz--) {
75:       x[*vi++] -= (*v++)*s1;
76:     }
77:     x[i] = s1;
78:   }
79:   /* backward solve the L^T */
80:   for (i=n-1; i>=0; i--) {
81:     v  = aa + diag[i] - 1;
82:     vi = aj + diag[i] - 1;
83:     nz = diag[i] - ai[i];
84:     s1 = x[i];
85:     while (nz--) {
86:       x[*vi--] -=  (*v--)*s1;
87:     }
88:   }
89:   VecRestoreArray(xx,&x);
90:   PetscLogFlops(2.0*(a->nz) - A->cmap->n);
91:   return(0);
92: }

```