Actual source code: baijsolvtrannat2.c

petsc-3.12.0 2019-09-29
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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: }