Actual source code: baijsolvtrannat2.c

petsc-3.14.3 2021-01-09
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```  1: #include <../src/mat/impls/baij/seq/baij.h>

3: PetscErrorCode MatSolveTranspose_SeqBAIJ_2_NaturalOrdering_inplace(Mat A,Vec bb,Vec xx)
4: {
5:   Mat_SeqBAIJ     *a=(Mat_SeqBAIJ*)A->data;
6:   PetscErrorCode  ierr;
7:   PetscInt        i,nz,idx,idt,oidx;
8:   const PetscInt  *diag = a->diag,*vi,n=a->mbs,*ai=a->i,*aj=a->j;
9:   const MatScalar *aa   =a->a,*v;
10:   PetscScalar     s1,s2,x1,x2,*x;

13:   VecCopy(bb,xx);
14:   VecGetArray(xx,&x);

16:   /* forward solve the U^T */
17:   idx = 0;
18:   for (i=0; i<n; i++) {

20:     v = aa + 4*diag[i];
21:     /* multiply by the inverse of the block diagonal */
22:     x1 = x[idx];   x2 = x[1+idx];
23:     s1 = v[0]*x1  +  v[1]*x2;
24:     s2 = v[2]*x1  +  v[3]*x2;
25:     v += 4;

27:     vi = aj + diag[i] + 1;
28:     nz = ai[i+1] - diag[i] - 1;
29:     while (nz--) {
30:       oidx       = 2*(*vi++);
31:       x[oidx]   -= v[0]*s1  +  v[1]*s2;
32:       x[oidx+1] -= v[2]*s1  +  v[3]*s2;
33:       v         += 4;
34:     }
35:     x[idx] = s1;x[1+idx] = s2;
36:     idx   += 2;
37:   }
38:   /* backward solve the L^T */
39:   for (i=n-1; i>=0; i--) {
40:     v   = aa + 4*diag[i] - 4;
41:     vi  = aj + diag[i] - 1;
42:     nz  = diag[i] - ai[i];
43:     idt = 2*i;
44:     s1  = x[idt];  s2 = x[1+idt];
45:     while (nz--) {
46:       idx       = 2*(*vi--);
47:       x[idx]   -=  v[0]*s1 +  v[1]*s2;
48:       x[idx+1] -=  v[2]*s1 +  v[3]*s2;
49:       v        -= 4;
50:     }
51:   }
52:   VecRestoreArray(xx,&x);
53:   PetscLogFlops(2.0*4.0*(a->nz) - 2.0*A->cmap->n);
54:   return(0);
55: }

57: PetscErrorCode MatSolveTranspose_SeqBAIJ_2_NaturalOrdering(Mat A,Vec bb,Vec xx)
58: {
59:   Mat_SeqBAIJ     *a=(Mat_SeqBAIJ*)A->data;
60:   PetscErrorCode  ierr;
61:   const PetscInt  n=a->mbs,*vi,*ai=a->i,*aj=a->j,*diag=a->diag;
62:   PetscInt        nz,idx,idt,j,i,oidx;
63:   const PetscInt  bs =A->rmap->bs,bs2=a->bs2;
64:   const MatScalar *aa=a->a,*v;
65:   PetscScalar     s1,s2,x1,x2,*x;

68:   VecCopy(bb,xx);
69:   VecGetArray(xx,&x);

71:   /* forward solve the U^T */
72:   idx = 0;
73:   for (i=0; i<n; i++) {
74:     v = aa + bs2*diag[i];
75:     /* multiply by the inverse of the block diagonal */
76:     x1 = x[idx];   x2 = x[1+idx];
77:     s1 = v[0]*x1  +  v[1]*x2;
78:     s2 = v[2]*x1  +  v[3]*x2;
79:     v -= bs2;

81:     vi = aj + diag[i] - 1;
82:     nz = diag[i] - diag[i+1] - 1;
83:     for (j=0; j>-nz; j--) {
84:       oidx       = bs*vi[j];
85:       x[oidx]   -= v[0]*s1  +  v[1]*s2;
86:       x[oidx+1] -= v[2]*s1  +  v[3]*s2;
87:       v         -= bs2;
88:     }
89:     x[idx] = s1;x[1+idx] = s2;
90:     idx   += bs;
91:   }
92:   /* backward solve the L^T */
93:   for (i=n-1; i>=0; i--) {
94:     v   = aa + bs2*ai[i];
95:     vi  = aj + ai[i];
96:     nz  = ai[i+1] - ai[i];
97:     idt = bs*i;
98:     s1  = x[idt];  s2 = x[1+idt];
99:     for (j=0; j<nz; j++) {
100:       idx       = bs*vi[j];
101:       x[idx]   -=  v[0]*s1 +  v[1]*s2;
102:       x[idx+1] -=  v[2]*s1 +  v[3]*s2;
103:       v        += bs2;
104:     }
105:   }
106:   VecRestoreArray(xx,&x);
107:   PetscLogFlops(2.0*bs2*(a->nz) - bs*A->cmap->n);
108:   return(0);
109: }
```