Actual source code: baijsolvtran2.c
petsc-3.10.5 2019-03-28
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      1:  #include <../src/mat/impls/baij/seq/baij.h>
      2:  #include <petsc/private/kernels/blockinvert.h>

      4: PetscErrorCode MatSolveTranspose_SeqBAIJ_2_inplace(Mat A,Vec bb,Vec xx)
      5: {
      6:   Mat_SeqBAIJ       *a   =(Mat_SeqBAIJ*)A->data;
      7:   IS                iscol=a->col,isrow=a->row;
      8:   PetscErrorCode    ierr;
      9:   const PetscInt    *r,*c,*rout,*cout;
     10:   const PetscInt    *diag=a->diag,n=a->mbs,*vi,*ai=a->i,*aj=a->j;
     11:   PetscInt          i,nz,idx,idt,ii,ic,ir,oidx;
     12:   const MatScalar   *aa=a->a,*v;
     13:   PetscScalar       s1,s2,x1,x2,*x,*t;
     14:   const PetscScalar *b;

     17:   VecGetArrayRead(bb,&b);
     18:   VecGetArray(xx,&x);
     19:   t    = a->solve_work;

     21:   ISGetIndices(isrow,&rout); r = rout;
     22:   ISGetIndices(iscol,&cout); c = cout;

     24:   /* copy the b into temp work space according to permutation */
     25:   ii = 0;
     26:   for (i=0; i<n; i++) {
     27:     ic      = 2*c[i];
     28:     t[ii]   = b[ic];
     29:     t[ii+1] = b[ic+1];
     30:     ii     += 2;
     31:   }

     33:   /* forward solve the U^T */
     34:   idx = 0;
     35:   for (i=0; i<n; i++) {

     37:     v = aa + 4*diag[i];
     38:     /* multiply by the inverse of the block diagonal */
     39:     x1 = t[idx];   x2 = t[1+idx];
     40:     s1 = v[0]*x1  +  v[1]*x2;
     41:     s2 = v[2]*x1  +  v[3]*x2;
     42:     v += 4;

     44:     vi = aj + diag[i] + 1;
     45:     nz = ai[i+1] - diag[i] - 1;
     46:     while (nz--) {
     47:       oidx       = 2*(*vi++);
     48:       t[oidx]   -= v[0]*s1  +  v[1]*s2;
     49:       t[oidx+1] -= v[2]*s1  +  v[3]*s2;
     50:       v         += 4;
     51:     }
     52:     t[idx] = s1;t[1+idx] = s2;
     53:     idx   += 2;
     54:   }
     55:   /* backward solve the L^T */
     56:   for (i=n-1; i>=0; i--) {
     57:     v   = aa + 4*diag[i] - 4;
     58:     vi  = aj + diag[i] - 1;
     59:     nz  = diag[i] - ai[i];
     60:     idt = 2*i;
     61:     s1  = t[idt];  s2 = t[1+idt];
     62:     while (nz--) {
     63:       idx       = 2*(*vi--);
     64:       t[idx]   -=  v[0]*s1 +  v[1]*s2;
     65:       t[idx+1] -=  v[2]*s1 +  v[3]*s2;
     66:       v        -= 4;
     67:     }
     68:   }

     70:   /* copy t into x according to permutation */
     71:   ii = 0;
     72:   for (i=0; i<n; i++) {
     73:     ir      = 2*r[i];
     74:     x[ir]   = t[ii];
     75:     x[ir+1] = t[ii+1];
     76:     ii     += 2;
     77:   }

     79:   ISRestoreIndices(isrow,&rout);
     80:   ISRestoreIndices(iscol,&cout);
     81:   VecRestoreArrayRead(bb,&b);
     82:   VecRestoreArray(xx,&x);
     83:   PetscLogFlops(2.0*4*(a->nz) - 2.0*A->cmap->n);
     84:   return(0);
     85: }

     87: PetscErrorCode MatSolveTranspose_SeqBAIJ_2(Mat A,Vec bb,Vec xx)
     88: {
     89:   Mat_SeqBAIJ       *a=(Mat_SeqBAIJ*)A->data;
     90:   PetscErrorCode    ierr;
     91:   IS                iscol=a->col,isrow=a->row;
     92:   const PetscInt    n    =a->mbs,*vi,*ai=a->i,*aj=a->j,*diag=a->diag;
     93:   const PetscInt    *r,*c,*rout,*cout;
     94:   PetscInt          nz,idx,idt,j,i,oidx,ii,ic,ir;
     95:   const PetscInt    bs =A->rmap->bs,bs2=a->bs2;
     96:   const MatScalar   *aa=a->a,*v;
     97:   PetscScalar       s1,s2,x1,x2,*x,*t;
     98:   const PetscScalar *b;

    101:   VecGetArrayRead(bb,&b);
    102:   VecGetArray(xx,&x);
    103:   t    = a->solve_work;

    105:   ISGetIndices(isrow,&rout); r = rout;
    106:   ISGetIndices(iscol,&cout); c = cout;

    108:   /* copy b into temp work space according to permutation */
    109:   for (i=0; i<n; i++) {
    110:     ii    = bs*i; ic = bs*c[i];
    111:     t[ii] = b[ic]; t[ii+1] = b[ic+1];
    112:   }

    114:   /* forward solve the U^T */
    115:   idx = 0;
    116:   for (i=0; i<n; i++) {
    117:     v = aa + bs2*diag[i];
    118:     /* multiply by the inverse of the block diagonal */
    119:     x1 = t[idx];   x2 = t[1+idx];
    120:     s1 = v[0]*x1  +  v[1]*x2;
    121:     s2 = v[2]*x1  +  v[3]*x2;
    122:     v -= bs2;

    124:     vi = aj + diag[i] - 1;
    125:     nz = diag[i] - diag[i+1] - 1;
    126:     for (j=0; j>-nz; j--) {
    127:       oidx       = bs*vi[j];
    128:       t[oidx]   -= v[0]*s1  +  v[1]*s2;
    129:       t[oidx+1] -= v[2]*s1  +  v[3]*s2;
    130:       v         -= bs2;
    131:     }
    132:     t[idx] = s1;t[1+idx] = s2;
    133:     idx   += bs;
    134:   }
    135:   /* backward solve the L^T */
    136:   for (i=n-1; i>=0; i--) {
    137:     v   = aa + bs2*ai[i];
    138:     vi  = aj + ai[i];
    139:     nz  = ai[i+1] - ai[i];
    140:     idt = bs*i;
    141:     s1  = t[idt];  s2 = t[1+idt];
    142:     for (j=0; j<nz; j++) {
    143:       idx       = bs*vi[j];
    144:       t[idx]   -=  v[0]*s1 +  v[1]*s2;
    145:       t[idx+1] -=  v[2]*s1 +  v[3]*s2;
    146:       v        += bs2;
    147:     }
    148:   }

    150:   /* copy t into x according to permutation */
    151:   for (i=0; i<n; i++) {
    152:     ii    = bs*i;  ir = bs*r[i];
    153:     x[ir] = t[ii];  x[ir+1] = t[ii+1];
    154:   }

    156:   ISRestoreIndices(isrow,&rout);
    157:   ISRestoreIndices(iscol,&cout);
    158:   VecRestoreArrayRead(bb,&b);
    159:   VecRestoreArray(xx,&x);
    160:   PetscLogFlops(2.0*bs2*(a->nz) - bs*A->cmap->n);
    161:   return(0);
    162: }