xref: /petsc/src/mat/impls/baij/seq/baijfact4.c (revision 421480d92be24cdb9933c60510b8e175c0a8d034)

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

PetscErrorCode MatILUFactorNumeric_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;
  const PetscInt *diag_offset;
  PetscInt        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;
  /* Since A is C and C is labeled as a factored matrix we need to lie to MatGetDiagonalMarkers_SeqBAIJ() to get it to compute the diagonals */
  A->factortype = MAT_FACTOR_NONE;
  PetscCall(MatGetDiagonalMarkers_SeqBAIJ(A, &diag_offset, NULL));
  A->factortype = MAT_FACTOR_ILU;
  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(PETSC_SUCCESS);
}