xref: /petsc/src/mat/impls/baij/seq/baijfact4.c (revision 9566063d113dddea24716c546802770db7481bc0)

/*
    Factorization code for BAIJ format.
*/
#include <../src/mat/impls/baij/seq/baij.h>
#include <petsc/private/kernels/blockinvert.h>

/* ----------------------------------------------------------- */
PetscErrorCode MatLUFactorNumeric_SeqBAIJ_N_inplace(Mat C,Mat A,const MatFactorInfo *info)
{
  Mat_SeqBAIJ    *a    = (Mat_SeqBAIJ*)A->data,*b = (Mat_SeqBAIJ*)C->data;
  IS             isrow = b->row,isicol = b->icol;
  const PetscInt *r,*ic;
  PetscInt       i,j,n = a->mbs,*bi = b->i,*bj = b->j;
  PetscInt       *ajtmpold,*ajtmp,nz,row,*ai=a->i,*aj=a->j,k,flg;
  PetscInt       *diag_offset=b->diag,diag,bs=A->rmap->bs,bs2 = a->bs2,*pj,*v_pivots;
  MatScalar      *ba = b->a,*aa = a->a,*pv,*v,*rtmp,*multiplier,*v_work,*pc,*w;
  PetscBool      allowzeropivot,zeropivotdetected;

  PetscFunctionBegin;
  PetscCall(ISGetIndices(isrow,&r));
  PetscCall(ISGetIndices(isicol,&ic));
  allowzeropivot = PetscNot(A->erroriffailure);

  PetscCall(PetscCalloc1(bs2*(n+1),&rtmp));
  /* generate work space needed by dense LU factorization */
  PetscCall(PetscMalloc3(bs,&v_work,bs2,&multiplier,bs,&v_pivots));

  for (i=0; i<n; i++) {
    nz    = bi[i+1] - bi[i];
    ajtmp = bj + bi[i];
    for  (j=0; j<nz; j++) {
      PetscCall(PetscArrayzero(rtmp+bs2*ajtmp[j],bs2));
    }
    /* load in initial (unfactored row) */
    nz       = ai[r[i]+1] - ai[r[i]];
    ajtmpold = aj + ai[r[i]];
    v        = aa + bs2*ai[r[i]];
    for (j=0; j<nz; j++) {
      PetscCall(PetscArraycpy(rtmp+bs2*ic[ajtmpold[j]],v+bs2*j,bs2));
    }
    row = *ajtmp++;
    while (row < i) {
      pc = rtmp + bs2*row;
/*      if (*pc) { */
      for (flg=0,k=0; k<bs2; k++) {
        if (pc[k]!=0.0) {
          flg = 1;
          break;
        }
      }
      if (flg) {
        pv = ba + bs2*diag_offset[row];
        pj = bj + diag_offset[row] + 1;
        PetscKernel_A_gets_A_times_B(bs,pc,pv,multiplier);
        nz  = bi[row+1] - diag_offset[row] - 1;
        pv += bs2;
        for (j=0; j<nz; j++) {
          PetscKernel_A_gets_A_minus_B_times_C(bs,rtmp+bs2*pj[j],pc,pv+bs2*j);
        }
        PetscCall(PetscLogFlops(2.0*bs*bs2*(nz+1.0)-bs));
      }
      row = *ajtmp++;
    }
    /* finished row so stick it into b->a */
    pv = ba + bs2*bi[i];
    pj = bj + bi[i];
    nz = bi[i+1] - bi[i];
    for (j=0; j<nz; j++) {
      PetscCall(PetscArraycpy(pv+bs2*j,rtmp+bs2*pj[j],bs2));
    }
    diag = diag_offset[i] - bi[i];
    /* invert diagonal block */
    w    = pv + bs2*diag;

    PetscCall(PetscKernel_A_gets_inverse_A(bs,w,v_pivots,v_work,allowzeropivot,&zeropivotdetected));
    if (zeropivotdetected) C->factorerrortype = MAT_FACTOR_NUMERIC_ZEROPIVOT;
  }

  PetscCall(PetscFree(rtmp));
  PetscCall(PetscFree3(v_work,multiplier,v_pivots));
  PetscCall(ISRestoreIndices(isicol,&ic));
  PetscCall(ISRestoreIndices(isrow,&r));

  C->ops->solve          = MatSolve_SeqBAIJ_N_inplace;
  C->ops->solvetranspose = MatSolveTranspose_SeqBAIJ_N_inplace;
  C->assembled           = PETSC_TRUE;

  PetscCall(PetscLogFlops(1.333333333333*bs*bs2*b->mbs)); /* from inverting diagonal blocks */
  PetscFunctionReturn(0);
}