xref: /petsc/src/mat/impls/scalapack/matscalapack.c (revision b8b5be36363868cf48bd7e7da4f4146957780db1)

#include <petsc/private/petscscalapack.h> /*I "petscmat.h" I*/

const char       ScaLAPACKCitation[] = "@BOOK{scalapack-user-guide,\n"
                                       "       AUTHOR = {L. S. Blackford and J. Choi and A. Cleary and E. D'Azevedo and\n"
                                       "                 J. Demmel and I. Dhillon and J. Dongarra and S. Hammarling and\n"
                                       "                 G. Henry and A. Petitet and K. Stanley and D. Walker and R. C. Whaley},\n"
                                       "       TITLE = {Sca{LAPACK} Users' Guide},\n"
                                       "       PUBLISHER = {SIAM},\n"
                                       "       ADDRESS = {Philadelphia, PA},\n"
                                       "       YEAR = 1997\n"
                                       "}\n";
static PetscBool ScaLAPACKCite       = PETSC_FALSE;

#define DEFAULT_BLOCKSIZE 64

/*
    The variable Petsc_ScaLAPACK_keyval is used to indicate an MPI attribute that
  is attached to a communicator, in this case the attribute is a Mat_ScaLAPACK_Grid
*/
static PetscMPIInt Petsc_ScaLAPACK_keyval = MPI_KEYVAL_INVALID;

static PetscErrorCode Petsc_ScaLAPACK_keyval_free(void)
{
  PetscFunctionBegin;
  PetscCall(PetscInfo(NULL, "Freeing Petsc_ScaLAPACK_keyval\n"));
  PetscCallMPI(MPI_Comm_free_keyval(&Petsc_ScaLAPACK_keyval));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatView_ScaLAPACK(Mat A, PetscViewer viewer)
{
  Mat_ScaLAPACK    *a = (Mat_ScaLAPACK *)A->data;
  PetscBool         isascii;
  PetscViewerFormat format;
  Mat               Adense;

  PetscFunctionBegin;
  PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii));
  if (isascii) {
    PetscCall(PetscViewerGetFormat(viewer, &format));
    if (format == PETSC_VIEWER_ASCII_INFO || format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
      PetscCall(PetscViewerASCIIPrintf(viewer, "block sizes: %d,%d\n", (int)a->mb, (int)a->nb));
      PetscCall(PetscViewerASCIIPrintf(viewer, "grid height=%d, grid width=%d\n", (int)a->grid->nprow, (int)a->grid->npcol));
      PetscCall(PetscViewerASCIIPrintf(viewer, "coordinates of process owning first row and column: (%d,%d)\n", (int)a->rsrc, (int)a->csrc));
      PetscCall(PetscViewerASCIIPrintf(viewer, "dimension of largest local matrix: %d x %d\n", (int)a->locr, (int)a->locc));
      PetscFunctionReturn(PETSC_SUCCESS);
    } else if (format == PETSC_VIEWER_ASCII_FACTOR_INFO) {
      PetscFunctionReturn(PETSC_SUCCESS);
    }
  }
  /* convert to dense format and call MatView() */
  PetscCall(MatConvert(A, MATDENSE, MAT_INITIAL_MATRIX, &Adense));
  PetscCall(MatView(Adense, viewer));
  PetscCall(MatDestroy(&Adense));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatGetInfo_ScaLAPACK(Mat A, MatInfoType flag, MatInfo *info)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  PetscLogDouble isend[2], irecv[2];

  PetscFunctionBegin;
  info->block_size = 1.0;

  isend[0] = a->lld * a->locc;  /* locally allocated */
  isend[1] = a->locr * a->locc; /* used submatrix */
  if (flag == MAT_LOCAL || flag == MAT_GLOBAL_MAX) {
    info->nz_allocated = isend[0];
    info->nz_used      = isend[1];
  } else if (flag == MAT_GLOBAL_MAX) {
    PetscCallMPI(MPIU_Allreduce(isend, irecv, 2, MPIU_PETSCLOGDOUBLE, MPI_MAX, PetscObjectComm((PetscObject)A)));
    info->nz_allocated = irecv[0];
    info->nz_used      = irecv[1];
  } else if (flag == MAT_GLOBAL_SUM) {
    PetscCallMPI(MPIU_Allreduce(isend, irecv, 2, MPIU_PETSCLOGDOUBLE, MPI_SUM, PetscObjectComm((PetscObject)A)));
    info->nz_allocated = irecv[0];
    info->nz_used      = irecv[1];
  }

  info->nz_unneeded       = 0;
  info->assemblies        = A->num_ass;
  info->mallocs           = 0;
  info->memory            = 0; /* REVIEW ME */
  info->fill_ratio_given  = 0;
  info->fill_ratio_needed = 0;
  info->factor_mallocs    = 0;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSetOption_ScaLAPACK(Mat A, MatOption op, PetscBool flg)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;

  PetscFunctionBegin;
  switch (op) {
  case MAT_NEW_NONZERO_LOCATIONS:
  case MAT_NEW_NONZERO_LOCATION_ERR:
  case MAT_NEW_NONZERO_ALLOCATION_ERR:
  case MAT_SYMMETRIC:
  case MAT_SORTED_FULL:
  case MAT_HERMITIAN:
    break;
  case MAT_ROW_ORIENTED:
    a->roworiented = flg;
    break;
  default:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported option %s", MatOptions[op]);
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSetValues_ScaLAPACK(Mat A, PetscInt nr, const PetscInt *rows, PetscInt nc, const PetscInt *cols, const PetscScalar *vals, InsertMode imode)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  PetscInt       i, j;
  PetscBLASInt   gridx, gcidx, lridx, lcidx, rsrc, csrc;
  PetscBool      roworiented = a->roworiented;

  PetscFunctionBegin;
  PetscCheck(imode == INSERT_VALUES || imode == ADD_VALUES, PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "No support for InsertMode %d", (int)imode);
  for (i = 0; i < nr; i++) {
    if (rows[i] < 0) continue;
    PetscCall(PetscBLASIntCast(rows[i] + 1, &gridx));
    for (j = 0; j < nc; j++) {
      if (cols[j] < 0) continue;
      PetscCall(PetscBLASIntCast(cols[j] + 1, &gcidx));
      PetscCallBLAS("SCALAPACKinfog2l", SCALAPACKinfog2l_(&gridx, &gcidx, a->desc, &a->grid->nprow, &a->grid->npcol, &a->grid->myrow, &a->grid->mycol, &lridx, &lcidx, &rsrc, &csrc));
      if (rsrc == a->grid->myrow && csrc == a->grid->mycol) {
        if (roworiented) {
          switch (imode) {
          case INSERT_VALUES:
            a->loc[lridx - 1 + (lcidx - 1) * a->lld] = vals[i * nc + j];
            break;
          default:
            a->loc[lridx - 1 + (lcidx - 1) * a->lld] += vals[i * nc + j];
            break;
          }
        } else {
          switch (imode) {
          case INSERT_VALUES:
            a->loc[lridx - 1 + (lcidx - 1) * a->lld] = vals[i + j * nr];
            break;
          default:
            a->loc[lridx - 1 + (lcidx - 1) * a->lld] += vals[i + j * nr];
            break;
          }
        }
      } else {
        PetscCheck(!A->nooffprocentries, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Setting off process entry even though MatSetOption(,MAT_NO_OFF_PROC_ENTRIES,PETSC_TRUE) was set");
        A->assembled = PETSC_FALSE;
        PetscCall(MatStashValuesRow_Private(&A->stash, rows[i], 1, cols + j, roworiented ? vals + i * nc + j : vals + i + j * nr, (PetscBool)(imode == ADD_VALUES)));
      }
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultXXXYYY_ScaLAPACK(Mat A, PetscBool transpose, PetscBool hermitian, PetscScalar beta, const PetscScalar *x, PetscScalar *y)
{
  Mat_ScaLAPACK  *a = (Mat_ScaLAPACK *)A->data;
  PetscScalar    *x2d, *y2d, alpha = 1.0;
  const PetscInt *ranges;
  PetscBLASInt    xdesc[9], ydesc[9], x2desc[9], y2desc[9], mb, nb, lszx, lszy, zero = 0, one = 1, xlld, ylld, info;

  PetscFunctionBegin;
  if (transpose) {
    /* create ScaLAPACK descriptors for vectors (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &mb)); /* x block size */
    PetscCall(PetscBLASIntCast(PetscMax(1, A->rmap->n), &xlld));
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(xdesc, &a->M, &one, &mb, &one, &zero, &zero, &a->grid->ictxcol, &xlld, &info));
    PetscCheckScaLapackInfo("descinit", info);
    PetscCall(PetscLayoutGetRanges(A->cmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &nb)); /* y block size */
    ylld = 1;
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ydesc, &one, &a->N, &one, &nb, &zero, &zero, &a->grid->ictxrow, &ylld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vectors */
    lszx = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
    lszy = SCALAPACKnumroc_(&a->N, &a->nb, &a->grid->mycol, &a->csrc, &a->grid->npcol);
    PetscCall(PetscMalloc2(lszx, &x2d, lszy, &y2d));
    PetscCall(PetscBLASIntCast(PetscMax(1, lszx), &xlld));

    /* create ScaLAPACK descriptors for vectors (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(x2desc, &a->M, &one, &a->mb, &one, &zero, &zero, &a->grid->ictxt, &xlld, &info));
    PetscCheckScaLapackInfo("descinit", info);
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(y2desc, &one, &a->N, &one, &a->nb, &zero, &zero, &a->grid->ictxt, &ylld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute x as a column of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, x, &one, &one, xdesc, x2d, &one, &one, x2desc, &a->grid->ictxcol));

    /* redistribute y as a row of a 2d matrix */
    if (beta != 0.0) PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&one, &a->N, y, &one, &one, ydesc, y2d, &one, &one, y2desc, &a->grid->ictxrow));

    /* call PBLAS subroutine */
    if (hermitian) PetscCallBLAS("PBLASgemv", PBLASgemv_("C", &a->M, &a->N, &alpha, a->loc, &one, &one, a->desc, x2d, &one, &one, x2desc, &one, &beta, y2d, &one, &one, y2desc, &one));
    else PetscCallBLAS("PBLASgemv", PBLASgemv_("T", &a->M, &a->N, &alpha, a->loc, &one, &one, a->desc, x2d, &one, &one, x2desc, &one, &beta, y2d, &one, &one, y2desc, &one));

    /* redistribute y from a row of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&one, &a->N, y2d, &one, &one, y2desc, y, &one, &one, ydesc, &a->grid->ictxrow));

  } else { /* non-transpose */

    /* create ScaLAPACK descriptors for vectors (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->cmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &nb)); /* x block size */
    xlld = 1;
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(xdesc, &one, &a->N, &one, &nb, &zero, &zero, &a->grid->ictxrow, &xlld, &info));
    PetscCheckScaLapackInfo("descinit", info);
    PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &mb)); /* y block size */
    PetscCall(PetscBLASIntCast(PetscMax(1, A->rmap->n), &ylld));
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ydesc, &a->M, &one, &mb, &one, &zero, &zero, &a->grid->ictxcol, &ylld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vectors */
    lszy = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
    lszx = SCALAPACKnumroc_(&a->N, &a->nb, &a->grid->mycol, &a->csrc, &a->grid->npcol);
    PetscCall(PetscMalloc2(lszx, &x2d, lszy, &y2d));
    PetscCall(PetscBLASIntCast(PetscMax(1, lszy), &ylld));

    /* create ScaLAPACK descriptors for vectors (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(x2desc, &one, &a->N, &one, &a->nb, &zero, &zero, &a->grid->ictxt, &xlld, &info));
    PetscCheckScaLapackInfo("descinit", info);
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(y2desc, &a->M, &one, &a->mb, &one, &zero, &zero, &a->grid->ictxt, &ylld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute x as a row of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&one, &a->N, x, &one, &one, xdesc, x2d, &one, &one, x2desc, &a->grid->ictxrow));

    /* redistribute y as a column of a 2d matrix */
    if (beta != 0.0) PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, y, &one, &one, ydesc, y2d, &one, &one, y2desc, &a->grid->ictxcol));

    /* call PBLAS subroutine */
    PetscCallBLAS("PBLASgemv", PBLASgemv_("N", &a->M, &a->N, &alpha, a->loc, &one, &one, a->desc, x2d, &one, &one, x2desc, &one, &beta, y2d, &one, &one, y2desc, &one));

    /* redistribute y from a column of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, y2d, &one, &one, y2desc, y, &one, &one, ydesc, &a->grid->ictxcol));
  }
  PetscCall(PetscFree2(x2d, y2d));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMult_ScaLAPACK(Mat A, Vec x, Vec y)
{
  const PetscScalar *xarray;
  PetscScalar       *yarray;

  PetscFunctionBegin;
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArray(y, &yarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_FALSE, PETSC_FALSE, 0.0, xarray, yarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArray(y, &yarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultTranspose_ScaLAPACK(Mat A, Vec x, Vec y)
{
  const PetscScalar *xarray;
  PetscScalar       *yarray;

  PetscFunctionBegin;
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArray(y, &yarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_TRUE, PETSC_FALSE, 0.0, xarray, yarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArray(y, &yarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultHermitianTranspose_ScaLAPACK(Mat A, Vec x, Vec y)
{
  const PetscScalar *xarray;
  PetscScalar       *yarray;

  PetscFunctionBegin;
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArrayWrite(y, &yarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_TRUE, PETSC_TRUE, 0.0, xarray, yarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArrayWrite(y, &yarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultAdd_ScaLAPACK(Mat A, Vec x, Vec y, Vec z)
{
  const PetscScalar *xarray;
  PetscScalar       *zarray;

  PetscFunctionBegin;
  if (y != z) PetscCall(VecCopy(y, z));
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArray(z, &zarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_FALSE, PETSC_FALSE, 1.0, xarray, zarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArray(z, &zarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultTransposeAdd_ScaLAPACK(Mat A, Vec x, Vec y, Vec z)
{
  const PetscScalar *xarray;
  PetscScalar       *zarray;

  PetscFunctionBegin;
  if (y != z) PetscCall(VecCopy(y, z));
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArray(z, &zarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_TRUE, PETSC_FALSE, 1.0, xarray, zarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArray(z, &zarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMultHermitianTransposeAdd_ScaLAPACK(Mat A, Vec x, Vec y, Vec z)
{
  const PetscScalar *xarray;
  PetscScalar       *zarray;

  PetscFunctionBegin;
  if (y != z) PetscCall(VecCopy(y, z));
  PetscCall(VecGetArrayRead(x, &xarray));
  PetscCall(VecGetArray(z, &zarray));
  PetscCall(MatMultXXXYYY_ScaLAPACK(A, PETSC_TRUE, PETSC_TRUE, 1.0, xarray, zarray));
  PetscCall(VecRestoreArrayRead(x, &xarray));
  PetscCall(VecRestoreArray(z, &zarray));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode MatMatMultNumeric_ScaLAPACK(Mat A, Mat B, Mat C)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data;
  Mat_ScaLAPACK *b    = (Mat_ScaLAPACK *)B->data;
  Mat_ScaLAPACK *c    = (Mat_ScaLAPACK *)C->data;
  PetscScalar    sone = 1.0, zero = 0.0;
  PetscBLASInt   one = 1;

  PetscFunctionBegin;
  PetscCallBLAS("PBLASgemm", PBLASgemm_("N", "N", &a->M, &b->N, &a->N, &sone, a->loc, &one, &one, a->desc, b->loc, &one, &one, b->desc, &zero, c->loc, &one, &one, c->desc));
  C->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode MatMatMultSymbolic_ScaLAPACK(Mat A, Mat B, PetscReal fill, Mat C)
{
  PetscFunctionBegin;
  PetscCall(MatSetSizes(C, A->rmap->n, B->cmap->n, PETSC_DECIDE, PETSC_DECIDE));
  PetscCall(MatSetType(C, MATSCALAPACK));
  PetscCall(MatSetUp(C));
  C->ops->matmultnumeric = MatMatMultNumeric_ScaLAPACK;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatTransposeMatMultNumeric_ScaLAPACK(Mat A, Mat B, Mat C)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data;
  Mat_ScaLAPACK *b    = (Mat_ScaLAPACK *)B->data;
  Mat_ScaLAPACK *c    = (Mat_ScaLAPACK *)C->data;
  PetscScalar    sone = 1.0, zero = 0.0;
  PetscBLASInt   one = 1;

  PetscFunctionBegin;
  PetscCallBLAS("PBLASgemm", PBLASgemm_("T", "N", &a->N, &b->N, &a->M, &sone, a->loc, &one, &one, a->desc, b->loc, &one, &one, b->desc, &zero, c->loc, &one, &one, c->desc));
  C->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatTransposeMatMultSymbolic_ScaLAPACK(Mat A, Mat B, PetscReal fill, Mat C)
{
  PetscFunctionBegin;
  PetscCall(MatSetSizes(C, A->cmap->n, B->cmap->n, PETSC_DECIDE, PETSC_DECIDE));
  PetscCall(MatSetType(C, MATSCALAPACK));
  PetscCall(MatSetUp(C));
  C->ops->transposematmultnumeric = MatTransposeMatMultNumeric_ScaLAPACK;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMatTransposeMultNumeric_ScaLAPACK(Mat A, Mat B, Mat C)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data;
  Mat_ScaLAPACK *b    = (Mat_ScaLAPACK *)B->data;
  Mat_ScaLAPACK *c    = (Mat_ScaLAPACK *)C->data;
  PetscScalar    sone = 1.0, zero = 0.0;
  PetscBLASInt   one = 1;

  PetscFunctionBegin;
  PetscCallBLAS("PBLASgemm", PBLASgemm_("N", "T", &a->M, &b->M, &a->N, &sone, a->loc, &one, &one, a->desc, b->loc, &one, &one, b->desc, &zero, c->loc, &one, &one, c->desc));
  C->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMatTransposeMultSymbolic_ScaLAPACK(Mat A, Mat B, PetscReal fill, Mat C)
{
  PetscFunctionBegin;
  PetscCall(MatSetSizes(C, A->rmap->n, B->rmap->n, PETSC_DECIDE, PETSC_DECIDE));
  PetscCall(MatSetType(C, MATSCALAPACK));
  PetscCall(MatSetUp(C));
  C->ops->mattransposemultnumeric = MatMatTransposeMultNumeric_ScaLAPACK;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatProductSetFromOptions_ScaLAPACK(Mat C)
{
  Mat_Product *product = C->product;

  PetscFunctionBegin;
  switch (product->type) {
  case MATPRODUCT_AB:
    C->ops->matmultsymbolic = MatMatMultSymbolic_ScaLAPACK;
    C->ops->productsymbolic = MatProductSymbolic_AB;
    break;
  case MATPRODUCT_AtB:
    C->ops->transposematmultsymbolic = MatTransposeMatMultSymbolic_ScaLAPACK;
    C->ops->productsymbolic          = MatProductSymbolic_AtB;
    break;
  case MATPRODUCT_ABt:
    C->ops->mattransposemultsymbolic = MatMatTransposeMultSymbolic_ScaLAPACK;
    C->ops->productsymbolic          = MatProductSymbolic_ABt;
    break;
  default:
    SETERRQ(PetscObjectComm((PetscObject)C), PETSC_ERR_SUP, "MatProduct type %s is not supported for ScaLAPACK and ScaLAPACK matrices", MatProductTypes[product->type]);
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatGetDiagonal_ScaLAPACK(Mat A, Vec D)
{
  Mat_ScaLAPACK  *a = (Mat_ScaLAPACK *)A->data;
  PetscScalar    *darray, *d2d, v;
  const PetscInt *ranges;
  PetscBLASInt    j, ddesc[9], d2desc[9], mb, nb, lszd, zero = 0, one = 1, dlld, info;

  PetscFunctionBegin;
  PetscCall(VecGetArray(D, &darray));

  if (A->rmap->N <= A->cmap->N) { /* row version */

    /* create ScaLAPACK descriptor for vector (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &mb)); /* D block size */
    PetscCall(PetscBLASIntCast(PetscMax(1, A->rmap->n), &dlld));
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ddesc, &a->M, &one, &mb, &one, &zero, &zero, &a->grid->ictxcol, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vector */
    lszd = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
    PetscCall(PetscCalloc1(lszd, &d2d));
    PetscCall(PetscBLASIntCast(PetscMax(1, lszd), &dlld));

    /* create ScaLAPACK descriptor for vector (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(d2desc, &a->M, &one, &a->mb, &one, &zero, &zero, &a->grid->ictxt, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* collect diagonal */
    for (j = 1; j <= a->M; j++) {
      PetscCallBLAS("SCALAPACKelget", SCALAPACKelget_("R", " ", &v, a->loc, &j, &j, a->desc));
      PetscCallBLAS("SCALAPACKelset", SCALAPACKelset_(d2d, &j, &one, d2desc, &v));
    }

    /* redistribute d from a column of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, d2d, &one, &one, d2desc, darray, &one, &one, ddesc, &a->grid->ictxcol));
    PetscCall(PetscFree(d2d));

  } else { /* column version */

    /* create ScaLAPACK descriptor for vector (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->cmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &nb)); /* D block size */
    dlld = 1;
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ddesc, &one, &a->N, &one, &nb, &zero, &zero, &a->grid->ictxrow, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vector */
    lszd = SCALAPACKnumroc_(&a->N, &a->nb, &a->grid->mycol, &a->csrc, &a->grid->npcol);
    PetscCall(PetscCalloc1(lszd, &d2d));

    /* create ScaLAPACK descriptor for vector (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(d2desc, &one, &a->N, &one, &a->nb, &zero, &zero, &a->grid->ictxt, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* collect diagonal */
    for (j = 1; j <= a->N; j++) {
      PetscCallBLAS("SCALAPACKelget", SCALAPACKelget_("C", " ", &v, a->loc, &j, &j, a->desc));
      PetscCallBLAS("SCALAPACKelset", SCALAPACKelset_(d2d, &one, &j, d2desc, &v));
    }

    /* redistribute d from a row of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&one, &a->N, d2d, &one, &one, d2desc, darray, &one, &one, ddesc, &a->grid->ictxrow));
    PetscCall(PetscFree(d2d));
  }

  PetscCall(VecRestoreArray(D, &darray));
  PetscCall(VecAssemblyBegin(D));
  PetscCall(VecAssemblyEnd(D));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatDiagonalScale_ScaLAPACK(Mat A, Vec L, Vec R)
{
  Mat_ScaLAPACK     *a = (Mat_ScaLAPACK *)A->data;
  const PetscScalar *d;
  const PetscInt    *ranges;
  PetscScalar       *d2d;
  PetscBLASInt       i, j, ddesc[9], d2desc[9], mb, nb, lszd, zero = 0, one = 1, dlld, info;

  PetscFunctionBegin;
  if (R) {
    PetscCall(VecGetArrayRead(R, &d));
    /* create ScaLAPACK descriptor for vector (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->cmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &nb)); /* D block size */
    dlld = 1;
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ddesc, &one, &a->N, &one, &nb, &zero, &zero, &a->grid->ictxrow, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vector */
    lszd = SCALAPACKnumroc_(&a->N, &a->nb, &a->grid->mycol, &a->csrc, &a->grid->npcol);
    PetscCall(PetscCalloc1(lszd, &d2d));

    /* create ScaLAPACK descriptor for vector (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(d2desc, &one, &a->N, &one, &a->nb, &zero, &zero, &a->grid->ictxt, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute d to a row of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&one, &a->N, d, &one, &one, ddesc, d2d, &one, &one, d2desc, &a->grid->ictxrow));

    /* broadcast along process columns */
    if (!a->grid->myrow) Cdgebs2d(a->grid->ictxt, "C", " ", 1, lszd, d2d, dlld);
    else Cdgebr2d(a->grid->ictxt, "C", " ", 1, lszd, d2d, dlld, 0, a->grid->mycol);

    /* local scaling */
    for (j = 0; j < a->locc; j++)
      for (i = 0; i < a->locr; i++) a->loc[i + j * a->lld] *= d2d[j];

    PetscCall(PetscFree(d2d));
    PetscCall(VecRestoreArrayRead(R, &d));
  }
  if (L) {
    PetscCall(VecGetArrayRead(L, &d));
    /* create ScaLAPACK descriptor for vector (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &mb)); /* D block size */
    PetscCall(PetscBLASIntCast(PetscMax(1, A->rmap->n), &dlld));
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(ddesc, &a->M, &one, &mb, &one, &zero, &zero, &a->grid->ictxcol, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* allocate 2d vector */
    lszd = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
    PetscCall(PetscCalloc1(lszd, &d2d));
    PetscCall(PetscBLASIntCast(PetscMax(1, lszd), &dlld));

    /* create ScaLAPACK descriptor for vector (2d block distribution) */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(d2desc, &a->M, &one, &a->mb, &one, &zero, &zero, &a->grid->ictxt, &dlld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute d to a column of a 2d matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, d, &one, &one, ddesc, d2d, &one, &one, d2desc, &a->grid->ictxcol));

    /* broadcast along process rows */
    if (!a->grid->mycol) Cdgebs2d(a->grid->ictxt, "R", " ", lszd, 1, d2d, dlld);
    else Cdgebr2d(a->grid->ictxt, "R", " ", lszd, 1, d2d, dlld, a->grid->myrow, 0);

    /* local scaling */
    for (i = 0; i < a->locr; i++)
      for (j = 0; j < a->locc; j++) a->loc[i + j * a->lld] *= d2d[i];

    PetscCall(PetscFree(d2d));
    PetscCall(VecRestoreArrayRead(L, &d));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMissingDiagonal_ScaLAPACK(Mat A, PetscBool *missing, PetscInt *d)
{
  PetscFunctionBegin;
  *missing = PETSC_FALSE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatScale_ScaLAPACK(Mat X, PetscScalar a)
{
  Mat_ScaLAPACK *x = (Mat_ScaLAPACK *)X->data;
  PetscBLASInt   n, one = 1;

  PetscFunctionBegin;
  n = x->lld * x->locc;
  PetscCallBLAS("BLASscal", BLASscal_(&n, &a, x->loc, &one));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatShift_ScaLAPACK(Mat X, PetscScalar alpha)
{
  Mat_ScaLAPACK *x = (Mat_ScaLAPACK *)X->data;
  PetscBLASInt   i, n;
  PetscScalar    v;

  PetscFunctionBegin;
  n = PetscMin(x->M, x->N);
  for (i = 1; i <= n; i++) {
    PetscCallBLAS("SCALAPACKelget", SCALAPACKelget_("-", " ", &v, x->loc, &i, &i, x->desc));
    v += alpha;
    PetscCallBLAS("SCALAPACKelset", SCALAPACKelset_(x->loc, &i, &i, x->desc, &v));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatAXPY_ScaLAPACK(Mat Y, PetscScalar alpha, Mat X, MatStructure str)
{
  Mat_ScaLAPACK *x    = (Mat_ScaLAPACK *)X->data;
  Mat_ScaLAPACK *y    = (Mat_ScaLAPACK *)Y->data;
  PetscBLASInt   one  = 1;
  PetscScalar    beta = 1.0;

  PetscFunctionBegin;
  MatScaLAPACKCheckDistribution(Y, 1, X, 3);
  PetscCallBLAS("SCALAPACKmatadd", SCALAPACKmatadd_(&x->M, &x->N, &alpha, x->loc, &one, &one, x->desc, &beta, y->loc, &one, &one, y->desc));
  PetscCall(PetscObjectStateIncrease((PetscObject)Y));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatCopy_ScaLAPACK(Mat A, Mat B, MatStructure str)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  Mat_ScaLAPACK *b = (Mat_ScaLAPACK *)B->data;

  PetscFunctionBegin;
  PetscCall(PetscArraycpy(b->loc, a->loc, a->lld * a->locc));
  PetscCall(PetscObjectStateIncrease((PetscObject)B));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatDuplicate_ScaLAPACK(Mat A, MatDuplicateOption op, Mat *B)
{
  Mat            Bs;
  MPI_Comm       comm;
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data, *b;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)A, &comm));
  PetscCall(MatCreate(comm, &Bs));
  PetscCall(MatSetSizes(Bs, A->rmap->n, A->cmap->n, PETSC_DECIDE, PETSC_DECIDE));
  PetscCall(MatSetType(Bs, MATSCALAPACK));
  b       = (Mat_ScaLAPACK *)Bs->data;
  b->M    = a->M;
  b->N    = a->N;
  b->mb   = a->mb;
  b->nb   = a->nb;
  b->rsrc = a->rsrc;
  b->csrc = a->csrc;
  PetscCall(MatSetUp(Bs));
  *B = Bs;
  if (op == MAT_COPY_VALUES) PetscCall(PetscArraycpy(b->loc, a->loc, a->lld * a->locc));
  Bs->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatTranspose_ScaLAPACK(Mat A, MatReuse reuse, Mat *B)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data, *b;
  Mat            Bs   = *B;
  PetscBLASInt   one  = 1;
  PetscScalar    sone = 1.0, zero = 0.0;
#if defined(PETSC_USE_COMPLEX)
  PetscInt i, j;
#endif

  PetscFunctionBegin;
  if (reuse == MAT_REUSE_MATRIX) PetscCall(MatTransposeCheckNonzeroState_Private(A, *B));
  PetscCheck(reuse == MAT_INITIAL_MATRIX, PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "Only MAT_INITIAL_MATRIX supported");
  PetscCall(MatCreateScaLAPACK(PetscObjectComm((PetscObject)A), a->nb, a->mb, a->N, a->M, a->csrc, a->rsrc, &Bs));
  *B = Bs;
  b  = (Mat_ScaLAPACK *)Bs->data;
  PetscCallBLAS("PBLAStran", PBLAStran_(&a->N, &a->M, &sone, a->loc, &one, &one, a->desc, &zero, b->loc, &one, &one, b->desc));
#if defined(PETSC_USE_COMPLEX)
  /* undo conjugation */
  for (i = 0; i < b->locr; i++)
    for (j = 0; j < b->locc; j++) b->loc[i + j * b->lld] = PetscConj(b->loc[i + j * b->lld]);
#endif
  Bs->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatConjugate_ScaLAPACK(Mat A)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  PetscInt       i, j;

  PetscFunctionBegin;
  for (i = 0; i < a->locr; i++)
    for (j = 0; j < a->locc; j++) a->loc[i + j * a->lld] = PetscConj(a->loc[i + j * a->lld]);
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatHermitianTranspose_ScaLAPACK(Mat A, MatReuse reuse, Mat *B)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data, *b;
  Mat            Bs   = *B;
  PetscBLASInt   one  = 1;
  PetscScalar    sone = 1.0, zero = 0.0;

  PetscFunctionBegin;
  PetscCheck(reuse == MAT_INITIAL_MATRIX, PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "Only MAT_INITIAL_MATRIX supported");
  PetscCall(MatCreateScaLAPACK(PetscObjectComm((PetscObject)A), a->nb, a->mb, a->N, a->M, a->csrc, a->rsrc, &Bs));
  *B = Bs;
  b  = (Mat_ScaLAPACK *)Bs->data;
  PetscCallBLAS("PBLAStran", PBLAStran_(&a->N, &a->M, &sone, a->loc, &one, &one, a->desc, &zero, b->loc, &one, &one, b->desc));
  Bs->assembled = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSolve_ScaLAPACK(Mat A, Vec B, Vec X)
{
  Mat_ScaLAPACK  *a = (Mat_ScaLAPACK *)A->data;
  PetscScalar    *x, *x2d;
  const PetscInt *ranges;
  PetscBLASInt    xdesc[9], x2desc[9], mb, lszx, zero = 0, one = 1, xlld, nrhs = 1, info;

  PetscFunctionBegin;
  PetscCall(VecCopy(B, X));
  PetscCall(VecGetArray(X, &x));

  /* create ScaLAPACK descriptor for a vector (1d block distribution) */
  PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
  PetscCall(PetscBLASIntCast(ranges[1], &mb)); /* x block size */
  PetscCall(PetscBLASIntCast(PetscMax(1, A->rmap->n), &xlld));
  PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(xdesc, &a->M, &one, &mb, &one, &zero, &zero, &a->grid->ictxcol, &xlld, &info));
  PetscCheckScaLapackInfo("descinit", info);

  /* allocate 2d vector */
  lszx = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
  PetscCall(PetscMalloc1(lszx, &x2d));
  PetscCall(PetscBLASIntCast(PetscMax(1, lszx), &xlld));

  /* create ScaLAPACK descriptor for a vector (2d block distribution) */
  PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(x2desc, &a->M, &one, &a->mb, &one, &zero, &zero, &a->grid->ictxt, &xlld, &info));
  PetscCheckScaLapackInfo("descinit", info);

  /* redistribute x as a column of a 2d matrix */
  PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, x, &one, &one, xdesc, x2d, &one, &one, x2desc, &a->grid->ictxcol));

  /* call ScaLAPACK subroutine */
  switch (A->factortype) {
  case MAT_FACTOR_LU:
    PetscCallBLAS("SCALAPACKgetrs", SCALAPACKgetrs_("N", &a->M, &nrhs, a->loc, &one, &one, a->desc, a->pivots, x2d, &one, &one, x2desc, &info));
    PetscCheckScaLapackInfo("getrs", info);
    break;
  case MAT_FACTOR_CHOLESKY:
    PetscCallBLAS("SCALAPACKpotrs", SCALAPACKpotrs_("L", &a->M, &nrhs, a->loc, &one, &one, a->desc, x2d, &one, &one, x2desc, &info));
    PetscCheckScaLapackInfo("potrs", info);
    break;
  default:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unfactored Matrix or Unsupported MatFactorType");
  }

  /* redistribute x from a column of a 2d matrix */
  PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &one, x2d, &one, &one, x2desc, x, &one, &one, xdesc, &a->grid->ictxcol));

  PetscCall(PetscFree(x2d));
  PetscCall(VecRestoreArray(X, &x));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSolveAdd_ScaLAPACK(Mat A, Vec B, Vec Y, Vec X)
{
  PetscFunctionBegin;
  PetscCall(MatSolve_ScaLAPACK(A, B, X));
  PetscCall(VecAXPY(X, 1, Y));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatMatSolve_ScaLAPACK(Mat A, Mat B, Mat X)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data, *x;
  PetscBool      flg1, flg2;
  PetscBLASInt   one = 1, info;
  Mat            C;
  MatType        type;

  PetscFunctionBegin;
  PetscCall(PetscObjectTypeCompare((PetscObject)B, MATSCALAPACK, &flg1));
  PetscCall(PetscObjectTypeCompare((PetscObject)X, MATSCALAPACK, &flg2));
  if (flg1 && flg2) MatScaLAPACKCheckDistribution(B, 2, X, 3);
  if (flg2) {
    if (flg1) PetscCall(MatCopy(B, X, SAME_NONZERO_PATTERN));
    else PetscCall(MatConvert(B, MATSCALAPACK, MAT_REUSE_MATRIX, &X));
    C = X;
  } else {
    PetscCall(MatConvert(B, MATSCALAPACK, MAT_INITIAL_MATRIX, &C));
  }
  x = (Mat_ScaLAPACK *)C->data;

  switch (A->factortype) {
  case MAT_FACTOR_LU:
    PetscCallBLAS("SCALAPACKgetrs", SCALAPACKgetrs_("N", &a->M, &x->N, a->loc, &one, &one, a->desc, a->pivots, x->loc, &one, &one, x->desc, &info));
    PetscCheckScaLapackInfo("getrs", info);
    break;
  case MAT_FACTOR_CHOLESKY:
    PetscCallBLAS("SCALAPACKpotrs", SCALAPACKpotrs_("L", &a->M, &x->N, a->loc, &one, &one, a->desc, x->loc, &one, &one, x->desc, &info));
    PetscCheckScaLapackInfo("potrs", info);
    break;
  default:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unfactored Matrix or Unsupported MatFactorType");
  }
  if (!flg2) {
    PetscCall(MatGetType(X, &type));
    PetscCall(MatConvert(C, type, MAT_REUSE_MATRIX, &X));
    PetscCall(MatDestroy(&C));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatLUFactor_ScaLAPACK(Mat A, IS row, IS col, const MatFactorInfo *factorinfo)
{
  Mat_ScaLAPACK *a   = (Mat_ScaLAPACK *)A->data;
  PetscBLASInt   one = 1, info;

  PetscFunctionBegin;
  if (!a->pivots) PetscCall(PetscMalloc1(a->locr + a->mb, &a->pivots));
  PetscCallBLAS("SCALAPACKgetrf", SCALAPACKgetrf_(&a->M, &a->N, a->loc, &one, &one, a->desc, a->pivots, &info));
  PetscCheckScaLapackInfo("getrf", info);
  A->factortype = MAT_FACTOR_LU;
  A->assembled  = PETSC_TRUE;

  PetscCall(PetscFree(A->solvertype));
  PetscCall(PetscStrallocpy(MATSOLVERSCALAPACK, &A->solvertype));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatLUFactorNumeric_ScaLAPACK(Mat F, Mat A, const MatFactorInfo *info)
{
  PetscFunctionBegin;
  PetscCall(MatCopy(A, F, SAME_NONZERO_PATTERN));
  PetscCall(MatLUFactor_ScaLAPACK(F, 0, 0, info));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatLUFactorSymbolic_ScaLAPACK(Mat F, Mat A, IS r, IS c, const MatFactorInfo *info)
{
  PetscFunctionBegin;
  /* F is created and allocated by MatGetFactor_scalapack_petsc(), skip this routine. */
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatCholeskyFactor_ScaLAPACK(Mat A, IS perm, const MatFactorInfo *factorinfo)
{
  Mat_ScaLAPACK *a   = (Mat_ScaLAPACK *)A->data;
  PetscBLASInt   one = 1, info;

  PetscFunctionBegin;
  PetscCallBLAS("SCALAPACKpotrf", SCALAPACKpotrf_("L", &a->M, a->loc, &one, &one, a->desc, &info));
  PetscCheckScaLapackInfo("potrf", info);
  A->factortype = MAT_FACTOR_CHOLESKY;
  A->assembled  = PETSC_TRUE;

  PetscCall(PetscFree(A->solvertype));
  PetscCall(PetscStrallocpy(MATSOLVERSCALAPACK, &A->solvertype));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatCholeskyFactorNumeric_ScaLAPACK(Mat F, Mat A, const MatFactorInfo *info)
{
  PetscFunctionBegin;
  PetscCall(MatCopy(A, F, SAME_NONZERO_PATTERN));
  PetscCall(MatCholeskyFactor_ScaLAPACK(F, 0, info));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatCholeskyFactorSymbolic_ScaLAPACK(Mat F, Mat A, IS perm, const MatFactorInfo *info)
{
  PetscFunctionBegin;
  /* F is created and allocated by MatGetFactor_scalapack_petsc(), skip this routine. */
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatFactorGetSolverType_scalapack_scalapack(Mat A, MatSolverType *type)
{
  PetscFunctionBegin;
  *type = MATSOLVERSCALAPACK;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatGetFactor_scalapack_scalapack(Mat A, MatFactorType ftype, Mat *F)
{
  Mat            B;
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;

  PetscFunctionBegin;
  /* Create the factorization matrix */
  PetscCall(MatCreateScaLAPACK(PetscObjectComm((PetscObject)A), a->mb, a->nb, a->M, a->N, a->rsrc, a->csrc, &B));
  B->trivialsymbolic = PETSC_TRUE;
  B->factortype      = ftype;
  PetscCall(PetscFree(B->solvertype));
  PetscCall(PetscStrallocpy(MATSOLVERSCALAPACK, &B->solvertype));

  PetscCall(PetscObjectComposeFunction((PetscObject)B, "MatFactorGetSolverType_C", MatFactorGetSolverType_scalapack_scalapack));
  *F = B;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatSolverTypeRegister_ScaLAPACK(void)
{
  PetscFunctionBegin;
  PetscCall(MatSolverTypeRegister(MATSOLVERSCALAPACK, MATSCALAPACK, MAT_FACTOR_LU, MatGetFactor_scalapack_scalapack));
  PetscCall(MatSolverTypeRegister(MATSOLVERSCALAPACK, MATSCALAPACK, MAT_FACTOR_CHOLESKY, MatGetFactor_scalapack_scalapack));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatNorm_ScaLAPACK(Mat A, NormType type, PetscReal *nrm)
{
  Mat_ScaLAPACK *a   = (Mat_ScaLAPACK *)A->data;
  PetscBLASInt   one = 1, lwork = 0;
  const char    *ntype;
  PetscScalar   *work = NULL, dummy;

  PetscFunctionBegin;
  switch (type) {
  case NORM_1:
    ntype = "1";
    lwork = PetscMax(a->locr, a->locc);
    break;
  case NORM_FROBENIUS:
    ntype = "F";
    work  = &dummy;
    break;
  case NORM_INFINITY:
    ntype = "I";
    lwork = PetscMax(a->locr, a->locc);
    break;
  default:
    SETERRQ(PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "Unsupported norm type");
  }
  if (lwork) PetscCall(PetscMalloc1(lwork, &work));
  *nrm = SCALAPACKlange_(ntype, &a->M, &a->N, a->loc, &one, &one, a->desc, work);
  if (lwork) PetscCall(PetscFree(work));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatZeroEntries_ScaLAPACK(Mat A)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;

  PetscFunctionBegin;
  PetscCall(PetscArrayzero(a->loc, a->lld * a->locc));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatGetOwnershipIS_ScaLAPACK(Mat A, IS *rows, IS *cols)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  PetscInt       i, n, nb, isrc, nproc, iproc, *idx;

  PetscFunctionBegin;
  if (rows) {
    n     = a->locr;
    nb    = a->mb;
    isrc  = a->rsrc;
    nproc = a->grid->nprow;
    iproc = a->grid->myrow;
    PetscCall(PetscMalloc1(n, &idx));
    for (i = 0; i < n; i++) idx[i] = nproc * nb * (i / nb) + i % nb + ((nproc + iproc - isrc) % nproc) * nb;
    PetscCall(ISCreateGeneral(PETSC_COMM_SELF, n, idx, PETSC_OWN_POINTER, rows));
  }
  if (cols) {
    n     = a->locc;
    nb    = a->nb;
    isrc  = a->csrc;
    nproc = a->grid->npcol;
    iproc = a->grid->mycol;
    PetscCall(PetscMalloc1(n, &idx));
    for (i = 0; i < n; i++) idx[i] = nproc * nb * (i / nb) + i % nb + ((nproc + iproc - isrc) % nproc) * nb;
    PetscCall(ISCreateGeneral(PETSC_COMM_SELF, n, idx, PETSC_OWN_POINTER, cols));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatConvert_ScaLAPACK_Dense(Mat A, MatType newtype, MatReuse reuse, Mat *B)
{
  Mat_ScaLAPACK     *a = (Mat_ScaLAPACK *)A->data;
  Mat                Bmpi;
  MPI_Comm           comm;
  PetscInt           i, M = A->rmap->N, N = A->cmap->N, m, n, rstart, rend, nz, ldb;
  const PetscInt    *ranges, *branges, *cwork;
  const PetscScalar *vwork;
  PetscBLASInt       bdesc[9], bmb, zero = 0, one = 1, lld, info;
  PetscScalar       *barray;
  PetscBool          differ = PETSC_FALSE;
  PetscMPIInt        size;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)A, &comm));
  PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));

  if (reuse == MAT_REUSE_MATRIX) { /* check if local sizes differ in A and B */
    PetscCallMPI(MPI_Comm_size(comm, &size));
    PetscCall(PetscLayoutGetRanges((*B)->rmap, &branges));
    for (i = 0; i < size; i++)
      if (ranges[i + 1] != branges[i + 1]) {
        differ = PETSC_TRUE;
        break;
      }
  }

  if (reuse == MAT_REUSE_MATRIX && differ) { /* special case, use auxiliary dense matrix */
    PetscCall(MatCreate(comm, &Bmpi));
    m = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(comm, &m, &M));
    n = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(comm, &n, &N));
    PetscCall(MatSetSizes(Bmpi, m, n, M, N));
    PetscCall(MatSetType(Bmpi, MATDENSE));
    PetscCall(MatSetUp(Bmpi));

    /* create ScaLAPACK descriptor for B (1d block distribution) */
    PetscCall(PetscBLASIntCast(ranges[1], &bmb)); /* row block size */
    PetscCall(MatDenseGetLDA(Bmpi, &ldb));
    PetscCall(PetscBLASIntCast(PetscMax(ldb, 1), &lld)); /* local leading dimension */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(bdesc, &a->M, &a->N, &bmb, &a->N, &zero, &zero, &a->grid->ictxcol, &lld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute matrix */
    PetscCall(MatDenseGetArray(Bmpi, &barray));
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &a->N, a->loc, &one, &one, a->desc, barray, &one, &one, bdesc, &a->grid->ictxcol));
    PetscCall(MatDenseRestoreArray(Bmpi, &barray));
    PetscCall(MatAssemblyBegin(Bmpi, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(Bmpi, MAT_FINAL_ASSEMBLY));

    /* transfer rows of auxiliary matrix to the final matrix B */
    PetscCall(MatGetOwnershipRange(Bmpi, &rstart, &rend));
    for (i = rstart; i < rend; i++) {
      PetscCall(MatGetRow(Bmpi, i, &nz, &cwork, &vwork));
      PetscCall(MatSetValues(*B, 1, &i, nz, cwork, vwork, INSERT_VALUES));
      PetscCall(MatRestoreRow(Bmpi, i, &nz, &cwork, &vwork));
    }
    PetscCall(MatAssemblyBegin(*B, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(*B, MAT_FINAL_ASSEMBLY));
    PetscCall(MatDestroy(&Bmpi));

  } else { /* normal cases */

    if (reuse == MAT_REUSE_MATRIX) Bmpi = *B;
    else {
      PetscCall(MatCreate(comm, &Bmpi));
      m = PETSC_DECIDE;
      PetscCall(PetscSplitOwnershipEqual(comm, &m, &M));
      n = PETSC_DECIDE;
      PetscCall(PetscSplitOwnershipEqual(comm, &n, &N));
      PetscCall(MatSetSizes(Bmpi, m, n, M, N));
      PetscCall(MatSetType(Bmpi, MATDENSE));
      PetscCall(MatSetUp(Bmpi));
    }

    /* create ScaLAPACK descriptor for B (1d block distribution) */
    PetscCall(PetscBLASIntCast(ranges[1], &bmb)); /* row block size */
    PetscCall(MatDenseGetLDA(Bmpi, &ldb));
    PetscCall(PetscBLASIntCast(PetscMax(ldb, 1), &lld)); /* local leading dimension */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(bdesc, &a->M, &a->N, &bmb, &a->N, &zero, &zero, &a->grid->ictxcol, &lld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute matrix */
    PetscCall(MatDenseGetArray(Bmpi, &barray));
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&a->M, &a->N, a->loc, &one, &one, a->desc, barray, &one, &one, bdesc, &a->grid->ictxcol));
    PetscCall(MatDenseRestoreArray(Bmpi, &barray));

    PetscCall(MatAssemblyBegin(Bmpi, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(Bmpi, MAT_FINAL_ASSEMBLY));
    if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &Bmpi));
    else *B = Bmpi;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static inline PetscErrorCode MatScaLAPACKCheckLayout(PetscLayout map, PetscBool *correct)
{
  const PetscInt *ranges;
  PetscMPIInt     size;
  PetscInt        i, n;

  PetscFunctionBegin;
  *correct = PETSC_TRUE;
  PetscCallMPI(MPI_Comm_size(map->comm, &size));
  if (size > 1) {
    PetscCall(PetscLayoutGetRanges(map, &ranges));
    n = ranges[1] - ranges[0];
    for (i = 1; i < size; i++)
      if (ranges[i + 1] - ranges[i] != n) break;
    *correct = (PetscBool)(i == size || (i == size - 1 && ranges[i + 1] - ranges[i] <= n));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatConvert_Dense_ScaLAPACK(Mat A, MatType newtype, MatReuse reuse, Mat *B)
{
  Mat_ScaLAPACK     *b;
  Mat                Bmpi;
  MPI_Comm           comm;
  PetscInt           M = A->rmap->N, N = A->cmap->N, m, n;
  const PetscInt    *ranges, *rows, *cols;
  PetscBLASInt       adesc[9], amb, zero = 0, one = 1, lld, info;
  const PetscScalar *aarray;
  IS                 ir, ic;
  PetscInt           lda;
  PetscBool          flg;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)A, &comm));

  if (reuse == MAT_REUSE_MATRIX) Bmpi = *B;
  else {
    PetscCall(MatCreate(comm, &Bmpi));
    m = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(comm, &m, &M));
    n = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(comm, &n, &N));
    PetscCall(MatSetSizes(Bmpi, m, n, M, N));
    PetscCall(MatSetType(Bmpi, MATSCALAPACK));
    PetscCall(MatSetUp(Bmpi));
  }
  b = (Mat_ScaLAPACK *)Bmpi->data;

  PetscCall(MatDenseGetLDA(A, &lda));
  PetscCall(MatDenseGetArrayRead(A, &aarray));
  PetscCall(MatScaLAPACKCheckLayout(A->rmap, &flg));
  if (flg) PetscCall(MatScaLAPACKCheckLayout(A->cmap, &flg));
  if (flg) { /* if the input Mat has a ScaLAPACK-compatible layout, use ScaLAPACK for the redistribution */
    /* create ScaLAPACK descriptor for A (1d block distribution) */
    PetscCall(PetscLayoutGetRanges(A->rmap, &ranges));
    PetscCall(PetscBLASIntCast(ranges[1], &amb));        /* row block size */
    PetscCall(PetscBLASIntCast(PetscMax(lda, 1), &lld)); /* local leading dimension */
    PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(adesc, &b->M, &b->N, &amb, &b->N, &zero, &zero, &b->grid->ictxcol, &lld, &info));
    PetscCheckScaLapackInfo("descinit", info);

    /* redistribute matrix */
    PetscCallBLAS("SCALAPACKgemr2d", SCALAPACKgemr2d_(&b->M, &b->N, aarray, &one, &one, adesc, b->loc, &one, &one, b->desc, &b->grid->ictxcol));
    Bmpi->nooffprocentries = PETSC_TRUE;
  } else { /* if the input Mat has a ScaLAPACK-incompatible layout, redistribute via MatSetValues() */
    PetscCheck(lda == A->rmap->n, PETSC_COMM_SELF, PETSC_ERR_SUP, "Leading dimension (%" PetscInt_FMT ") different than local number of rows (%" PetscInt_FMT ")", lda, A->rmap->n);
    b->roworiented = PETSC_FALSE;
    PetscCall(MatGetOwnershipIS(A, &ir, &ic));
    PetscCall(ISGetIndices(ir, &rows));
    PetscCall(ISGetIndices(ic, &cols));
    PetscCall(MatSetValues(Bmpi, A->rmap->n, rows, A->cmap->N, cols, aarray, INSERT_VALUES));
    PetscCall(ISRestoreIndices(ir, &rows));
    PetscCall(ISRestoreIndices(ic, &cols));
    PetscCall(ISDestroy(&ic));
    PetscCall(ISDestroy(&ir));
  }
  PetscCall(MatDenseRestoreArrayRead(A, &aarray));
  PetscCall(MatAssemblyBegin(Bmpi, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(Bmpi, MAT_FINAL_ASSEMBLY));
  if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &Bmpi));
  else *B = Bmpi;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatConvert_AIJ_ScaLAPACK(Mat A, MatType newtype, MatReuse reuse, Mat *newmat)
{
  Mat                mat_scal;
  PetscInt           M = A->rmap->N, N = A->cmap->N, rstart = A->rmap->rstart, rend = A->rmap->rend, m, n, row, ncols;
  const PetscInt    *cols;
  const PetscScalar *vals;

  PetscFunctionBegin;
  if (reuse == MAT_REUSE_MATRIX) {
    mat_scal = *newmat;
    PetscCall(MatZeroEntries(mat_scal));
  } else {
    PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &mat_scal));
    m = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(PetscObjectComm((PetscObject)A), &m, &M));
    n = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(PetscObjectComm((PetscObject)A), &n, &N));
    PetscCall(MatSetSizes(mat_scal, m, n, M, N));
    PetscCall(MatSetType(mat_scal, MATSCALAPACK));
    PetscCall(MatSetUp(mat_scal));
  }
  for (row = rstart; row < rend; row++) {
    PetscCall(MatGetRow(A, row, &ncols, &cols, &vals));
    PetscCall(MatSetValues(mat_scal, 1, &row, ncols, cols, vals, INSERT_VALUES));
    PetscCall(MatRestoreRow(A, row, &ncols, &cols, &vals));
  }
  PetscCall(MatAssemblyBegin(mat_scal, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(mat_scal, MAT_FINAL_ASSEMBLY));

  if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &mat_scal));
  else *newmat = mat_scal;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatConvert_SBAIJ_ScaLAPACK(Mat A, MatType newtype, MatReuse reuse, Mat *newmat)
{
  Mat                mat_scal;
  PetscInt           M = A->rmap->N, N = A->cmap->N, m, n, row, ncols, j, rstart = A->rmap->rstart, rend = A->rmap->rend;
  const PetscInt    *cols;
  const PetscScalar *vals;
  PetscScalar        v;

  PetscFunctionBegin;
  if (reuse == MAT_REUSE_MATRIX) {
    mat_scal = *newmat;
    PetscCall(MatZeroEntries(mat_scal));
  } else {
    PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &mat_scal));
    m = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(PetscObjectComm((PetscObject)A), &m, &M));
    n = PETSC_DECIDE;
    PetscCall(PetscSplitOwnershipEqual(PetscObjectComm((PetscObject)A), &n, &N));
    PetscCall(MatSetSizes(mat_scal, m, n, M, N));
    PetscCall(MatSetType(mat_scal, MATSCALAPACK));
    PetscCall(MatSetUp(mat_scal));
  }
  PetscCall(MatGetRowUpperTriangular(A));
  for (row = rstart; row < rend; row++) {
    PetscCall(MatGetRow(A, row, &ncols, &cols, &vals));
    PetscCall(MatSetValues(mat_scal, 1, &row, ncols, cols, vals, ADD_VALUES));
    for (j = 0; j < ncols; j++) { /* lower triangular part */
      if (cols[j] == row) continue;
      v = A->hermitian == PETSC_BOOL3_TRUE ? PetscConj(vals[j]) : vals[j];
      PetscCall(MatSetValues(mat_scal, 1, &cols[j], 1, &row, &v, ADD_VALUES));
    }
    PetscCall(MatRestoreRow(A, row, &ncols, &cols, &vals));
  }
  PetscCall(MatRestoreRowUpperTriangular(A));
  PetscCall(MatAssemblyBegin(mat_scal, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(mat_scal, MAT_FINAL_ASSEMBLY));

  if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &mat_scal));
  else *newmat = mat_scal;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatScaLAPACKSetPreallocation(Mat A)
{
  Mat_ScaLAPACK *a  = (Mat_ScaLAPACK *)A->data;
  PetscInt       sz = 0;

  PetscFunctionBegin;
  PetscCall(PetscLayoutSetUp(A->rmap));
  PetscCall(PetscLayoutSetUp(A->cmap));
  if (!a->lld) a->lld = a->locr;

  PetscCall(PetscFree(a->loc));
  PetscCall(PetscIntMultError(a->lld, a->locc, &sz));
  PetscCall(PetscCalloc1(sz, &a->loc));

  A->preallocated = PETSC_TRUE;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatDestroy_ScaLAPACK(Mat A)
{
  Mat_ScaLAPACK      *a = (Mat_ScaLAPACK *)A->data;
  Mat_ScaLAPACK_Grid *grid;
  PetscMPIInt         iflg;
  MPI_Comm            icomm;

  PetscFunctionBegin;
  PetscCall(MatStashDestroy_Private(&A->stash));
  PetscCall(PetscFree(a->loc));
  PetscCall(PetscFree(a->pivots));
  PetscCall(PetscCommDuplicate(PetscObjectComm((PetscObject)A), &icomm, NULL));
  PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_ScaLAPACK_keyval, (void **)&grid, &iflg));
  if (--grid->grid_refct == 0) {
    Cblacs_gridexit(grid->ictxt);
    Cblacs_gridexit(grid->ictxrow);
    Cblacs_gridexit(grid->ictxcol);
    PetscCall(PetscFree(grid));
    PetscCallMPI(MPI_Comm_delete_attr(icomm, Petsc_ScaLAPACK_keyval));
  }
  PetscCall(PetscCommDestroy(&icomm));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatGetOwnershipIS_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatFactorGetSolverType_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatScaLAPACKSetBlockSizes_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatScaLAPACKGetBlockSizes_C", NULL));
  PetscCall(PetscFree(A->data));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatSetUp_ScaLAPACK(Mat A)
{
  Mat_ScaLAPACK *a    = (Mat_ScaLAPACK *)A->data;
  PetscBLASInt   info = 0;
  PetscBool      flg;

  PetscFunctionBegin;
  PetscCall(PetscLayoutSetUp(A->rmap));
  PetscCall(PetscLayoutSetUp(A->cmap));

  /* check that the layout is as enforced by MatCreateScaLAPACK() */
  PetscCall(MatScaLAPACKCheckLayout(A->rmap, &flg));
  PetscCheck(flg, A->rmap->comm, PETSC_ERR_SUP, "MATSCALAPACK must have equal local row sizes in all processes (except possibly the last one), consider using MatCreateScaLAPACK");
  PetscCall(MatScaLAPACKCheckLayout(A->cmap, &flg));
  PetscCheck(flg, A->cmap->comm, PETSC_ERR_SUP, "MATSCALAPACK must have equal local column sizes in all processes (except possibly the last one), consider using MatCreateScaLAPACK");

  /* compute local sizes */
  PetscCall(PetscBLASIntCast(A->rmap->N, &a->M));
  PetscCall(PetscBLASIntCast(A->cmap->N, &a->N));
  a->locr = SCALAPACKnumroc_(&a->M, &a->mb, &a->grid->myrow, &a->rsrc, &a->grid->nprow);
  a->locc = SCALAPACKnumroc_(&a->N, &a->nb, &a->grid->mycol, &a->csrc, &a->grid->npcol);
  a->lld  = PetscMax(1, a->locr);

  /* allocate local array */
  PetscCall(MatScaLAPACKSetPreallocation(A));

  /* set up ScaLAPACK descriptor */
  PetscCallBLAS("SCALAPACKdescinit", SCALAPACKdescinit_(a->desc, &a->M, &a->N, &a->mb, &a->nb, &a->rsrc, &a->csrc, &a->grid->ictxt, &a->lld, &info));
  PetscCheckScaLapackInfo("descinit", info);
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatAssemblyBegin_ScaLAPACK(Mat A, MatAssemblyType type)
{
  PetscInt nstash, reallocs;

  PetscFunctionBegin;
  if (A->nooffprocentries) PetscFunctionReturn(PETSC_SUCCESS);
  PetscCall(MatStashScatterBegin_Private(A, &A->stash, NULL));
  PetscCall(MatStashGetInfo_Private(&A->stash, &nstash, &reallocs));
  PetscCall(PetscInfo(A, "Stash has %" PetscInt_FMT " entries, uses %" PetscInt_FMT " mallocs.\n", nstash, reallocs));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatAssemblyEnd_ScaLAPACK(Mat A, MatAssemblyType type)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;
  PetscMPIInt    n;
  PetscInt       i, flg, *row, *col;
  PetscScalar   *val;
  PetscBLASInt   gridx, gcidx, lridx, lcidx, rsrc, csrc;

  PetscFunctionBegin;
  if (A->nooffprocentries) PetscFunctionReturn(PETSC_SUCCESS);
  while (1) {
    PetscCall(MatStashScatterGetMesg_Private(&A->stash, &n, &row, &col, &val, &flg));
    if (!flg) break;
    for (i = 0; i < n; i++) {
      PetscCall(PetscBLASIntCast(row[i] + 1, &gridx));
      PetscCall(PetscBLASIntCast(col[i] + 1, &gcidx));
      PetscCallBLAS("SCALAPACKinfog2l", SCALAPACKinfog2l_(&gridx, &gcidx, a->desc, &a->grid->nprow, &a->grid->npcol, &a->grid->myrow, &a->grid->mycol, &lridx, &lcidx, &rsrc, &csrc));
      PetscCheck(rsrc == a->grid->myrow && csrc == a->grid->mycol, PetscObjectComm((PetscObject)A), PETSC_ERR_LIB, "Something went wrong, received value does not belong to this process");
      switch (A->insertmode) {
      case INSERT_VALUES:
        a->loc[lridx - 1 + (lcidx - 1) * a->lld] = val[i];
        break;
      case ADD_VALUES:
        a->loc[lridx - 1 + (lcidx - 1) * a->lld] += val[i];
        break;
      default:
        SETERRQ(PetscObjectComm((PetscObject)A), PETSC_ERR_SUP, "No support for InsertMode %d", (int)A->insertmode);
      }
    }
  }
  PetscCall(MatStashScatterEnd_Private(&A->stash));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatLoad_ScaLAPACK(Mat newMat, PetscViewer viewer)
{
  Mat      Adense, As;
  MPI_Comm comm;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)newMat, &comm));
  PetscCall(MatCreate(comm, &Adense));
  PetscCall(MatSetType(Adense, MATDENSE));
  PetscCall(MatLoad(Adense, viewer));
  PetscCall(MatConvert(Adense, MATSCALAPACK, MAT_INITIAL_MATRIX, &As));
  PetscCall(MatDestroy(&Adense));
  PetscCall(MatHeaderReplace(newMat, &As));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static struct _MatOps MatOps_Values = {MatSetValues_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       MatMult_ScaLAPACK,
                                       /* 4*/ MatMultAdd_ScaLAPACK,
                                       MatMultTranspose_ScaLAPACK,
                                       MatMultTransposeAdd_ScaLAPACK,
                                       MatSolve_ScaLAPACK,
                                       MatSolveAdd_ScaLAPACK,
                                       NULL,
                                       /*10*/ NULL,
                                       MatLUFactor_ScaLAPACK,
                                       MatCholeskyFactor_ScaLAPACK,
                                       NULL,
                                       MatTranspose_ScaLAPACK,
                                       /*15*/ MatGetInfo_ScaLAPACK,
                                       NULL,
                                       MatGetDiagonal_ScaLAPACK,
                                       MatDiagonalScale_ScaLAPACK,
                                       MatNorm_ScaLAPACK,
                                       /*20*/ MatAssemblyBegin_ScaLAPACK,
                                       MatAssemblyEnd_ScaLAPACK,
                                       MatSetOption_ScaLAPACK,
                                       MatZeroEntries_ScaLAPACK,
                                       /*24*/ NULL,
                                       MatLUFactorSymbolic_ScaLAPACK,
                                       MatLUFactorNumeric_ScaLAPACK,
                                       MatCholeskyFactorSymbolic_ScaLAPACK,
                                       MatCholeskyFactorNumeric_ScaLAPACK,
                                       /*29*/ MatSetUp_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*34*/ MatDuplicate_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*39*/ MatAXPY_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       NULL,
                                       MatCopy_ScaLAPACK,
                                       /*44*/ NULL,
                                       MatScale_ScaLAPACK,
                                       MatShift_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       /*49*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*54*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*59*/ NULL,
                                       MatDestroy_ScaLAPACK,
                                       MatView_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       /*64*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*69*/ NULL,
                                       MatConvert_ScaLAPACK_Dense,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*74*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       MatLoad_ScaLAPACK,
                                       /*79*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*84*/ NULL,
                                       MatMatMultNumeric_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       MatMatTransposeMultNumeric_ScaLAPACK,
                                       /*89*/ NULL,
                                       MatProductSetFromOptions_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       MatConjugate_ScaLAPACK,
                                       /*94*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*99*/ NULL,
                                       MatMatSolve_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*104*/ MatMissingDiagonal_ScaLAPACK,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*109*/ NULL,
                                       NULL,
                                       MatHermitianTranspose_ScaLAPACK,
                                       MatMultHermitianTranspose_ScaLAPACK,
                                       MatMultHermitianTransposeAdd_ScaLAPACK,
                                       /*114*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*119*/ NULL,
                                       NULL,
                                       NULL,
                                       MatTransposeMatMultNumeric_ScaLAPACK,
                                       NULL,
                                       /*124*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*129*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*134*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       /*140*/ NULL,
                                       NULL,
                                       NULL,
                                       NULL};

static PetscErrorCode MatStashScatterBegin_ScaLAPACK(Mat mat, MatStash *stash, PetscInt *owners)
{
  PetscInt          *owner, *startv, *starti, bs2;
  PetscInt           size = stash->size, nsends;
  PetscInt          *sindices, **rindices, j, l;
  PetscScalar      **rvalues, *svalues;
  MPI_Comm           comm = stash->comm;
  MPI_Request       *send_waits, *recv_waits, *recv_waits1, *recv_waits2;
  PetscMPIInt        tag1 = stash->tag1, tag2 = stash->tag2, *sizes, *nlengths, nreceives, insends, ii;
  PetscInt          *sp_idx, *sp_idy;
  PetscScalar       *sp_val;
  PetscMatStashSpace space, space_next;
  PetscBLASInt       gridx, gcidx, lridx, lcidx, rsrc, csrc;
  Mat_ScaLAPACK     *a = (Mat_ScaLAPACK *)mat->data;

  PetscFunctionBegin;
  { /* make sure all processors are either in INSERTMODE or ADDMODE */
    InsertMode addv;
    PetscCallMPI(MPIU_Allreduce((PetscEnum *)&mat->insertmode, (PetscEnum *)&addv, 1, MPIU_ENUM, MPI_BOR, PetscObjectComm((PetscObject)mat)));
    PetscCheck(addv != (ADD_VALUES | INSERT_VALUES), PetscObjectComm((PetscObject)mat), PETSC_ERR_ARG_WRONGSTATE, "Some processors inserted others added");
    mat->insertmode = addv; /* in case this processor had no cache */
  }

  bs2 = stash->bs * stash->bs;

  /*  first count number of contributors to each processor */
  PetscCall(PetscCalloc1(size, &nlengths));
  PetscCall(PetscMalloc1(stash->n + 1, &owner));

  ii = j = 0;
  space  = stash->space_head;
  while (space) {
    space_next = space->next;
    for (l = 0; l < space->local_used; l++) {
      PetscCall(PetscBLASIntCast(space->idx[l] + 1, &gridx));
      PetscCall(PetscBLASIntCast(space->idy[l] + 1, &gcidx));
      PetscCallBLAS("SCALAPACKinfog2l", SCALAPACKinfog2l_(&gridx, &gcidx, a->desc, &a->grid->nprow, &a->grid->npcol, &a->grid->myrow, &a->grid->mycol, &lridx, &lcidx, &rsrc, &csrc));
      j = Cblacs_pnum(a->grid->ictxt, rsrc, csrc);
      nlengths[j]++;
      owner[ii] = j;
      ii++;
    }
    space = space_next;
  }

  /* Now check what procs get messages - and compute nsends. */
  PetscCall(PetscCalloc1(size, &sizes));
  nsends = 0;
  for (PetscMPIInt i = 0; i < size; i++) {
    if (nlengths[i]) {
      sizes[i] = 1;
      nsends++;
    }
  }

  {
    PetscMPIInt *onodes, *olengths;

    /* Determine the number of messages to expect, their lengths, from from-ids */
    PetscCall(PetscGatherNumberOfMessages(comm, sizes, nlengths, &nreceives));
    PetscCall(PetscMPIIntCast(nsends, &insends));
    PetscCall(PetscGatherMessageLengths(comm, insends, nreceives, nlengths, &onodes, &olengths));
    /* since clubbing row,col - lengths are multiplied by 2 */
    for (PetscMPIInt i = 0; i < nreceives; i++) olengths[i] *= 2;
    PetscCall(PetscPostIrecvInt(comm, tag1, nreceives, onodes, olengths, &rindices, &recv_waits1));
    /* values are size 'bs2' lengths (and remove earlier factor 2 */
    for (PetscMPIInt i = 0; i < nreceives; i++) olengths[i] = (PetscMPIInt)(olengths[i] * bs2 / 2);
    PetscCall(PetscPostIrecvScalar(comm, tag2, nreceives, onodes, olengths, &rvalues, &recv_waits2));
    PetscCall(PetscFree(onodes));
    PetscCall(PetscFree(olengths));
  }

  /* do sends:
      1) starts[i] gives the starting index in svalues for stuff going to
         the ith processor
  */
  PetscCall(PetscMalloc2(bs2 * stash->n, &svalues, 2 * (stash->n + 1), &sindices));
  PetscCall(PetscMalloc1(2 * nsends, &send_waits));
  PetscCall(PetscMalloc2(size, &startv, size, &starti));
  /* use 2 sends the first with all_a, the next with all_i and all_j */
  startv[0] = 0;
  starti[0] = 0;
  for (PetscMPIInt i = 1; i < size; i++) {
    startv[i] = startv[i - 1] + nlengths[i - 1];
    starti[i] = starti[i - 1] + 2 * nlengths[i - 1];
  }

  ii    = 0;
  space = stash->space_head;
  while (space) {
    space_next = space->next;
    sp_idx     = space->idx;
    sp_idy     = space->idy;
    sp_val     = space->val;
    for (l = 0; l < space->local_used; l++) {
      j = owner[ii];
      if (bs2 == 1) {
        svalues[startv[j]] = sp_val[l];
      } else {
        PetscInt     k;
        PetscScalar *buf1, *buf2;
        buf1 = svalues + bs2 * startv[j];
        buf2 = space->val + bs2 * l;
        for (k = 0; k < bs2; k++) buf1[k] = buf2[k];
      }
      sindices[starti[j]]               = sp_idx[l];
      sindices[starti[j] + nlengths[j]] = sp_idy[l];
      startv[j]++;
      starti[j]++;
      ii++;
    }
    space = space_next;
  }
  startv[0] = 0;
  for (PetscMPIInt i = 1; i < size; i++) startv[i] = startv[i - 1] + nlengths[i - 1];

  for (PetscMPIInt i = 0, count = 0; i < size; i++) {
    if (sizes[i]) {
      PetscCallMPI(MPIU_Isend(sindices + 2 * startv[i], 2 * nlengths[i], MPIU_INT, i, tag1, comm, send_waits + count++));
      PetscCallMPI(MPIU_Isend(svalues + bs2 * startv[i], bs2 * nlengths[i], MPIU_SCALAR, i, tag2, comm, send_waits + count++));
    }
  }
#if defined(PETSC_USE_INFO)
  PetscCall(PetscInfo(NULL, "No of messages: %" PetscInt_FMT "\n", nsends));
  for (PetscMPIInt i = 0; i < size; i++) {
    if (sizes[i]) PetscCall(PetscInfo(NULL, "Mesg_to: %d: size: %zu bytes\n", i, (size_t)(nlengths[i] * (bs2 * sizeof(PetscScalar) + 2 * sizeof(PetscInt)))));
  }
#endif
  PetscCall(PetscFree(nlengths));
  PetscCall(PetscFree(owner));
  PetscCall(PetscFree2(startv, starti));
  PetscCall(PetscFree(sizes));

  /* recv_waits need to be contiguous for MatStashScatterGetMesg_Private() */
  PetscCall(PetscMalloc1(2 * nreceives, &recv_waits));

  for (PetscMPIInt i = 0; i < nreceives; i++) {
    recv_waits[2 * i]     = recv_waits1[i];
    recv_waits[2 * i + 1] = recv_waits2[i];
  }
  stash->recv_waits = recv_waits;

  PetscCall(PetscFree(recv_waits1));
  PetscCall(PetscFree(recv_waits2));

  stash->svalues         = svalues;
  stash->sindices        = sindices;
  stash->rvalues         = rvalues;
  stash->rindices        = rindices;
  stash->send_waits      = send_waits;
  stash->nsends          = (PetscMPIInt)nsends;
  stash->nrecvs          = nreceives;
  stash->reproduce_count = 0;
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatScaLAPACKSetBlockSizes_ScaLAPACK(Mat A, PetscInt mb, PetscInt nb)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;

  PetscFunctionBegin;
  PetscCheck(!A->preallocated, PETSC_COMM_SELF, PETSC_ERR_ORDER, "Cannot change block sizes after MatSetUp");
  PetscCheck(mb >= 1 || mb == PETSC_DECIDE, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "mb %" PetscInt_FMT " must be at least 1", mb);
  PetscCheck(nb >= 1 || nb == PETSC_DECIDE, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "nb %" PetscInt_FMT " must be at least 1", nb);
  PetscCall(PetscBLASIntCast((mb == PETSC_DECIDE) ? DEFAULT_BLOCKSIZE : mb, &a->mb));
  PetscCall(PetscBLASIntCast((nb == PETSC_DECIDE) ? a->mb : nb, &a->nb));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  MatScaLAPACKSetBlockSizes - Sets the block sizes to be used for the distribution of
  the `MATSCALAPACK` matrix

  Logically Collective

  Input Parameters:
+ A  - a `MATSCALAPACK` matrix
. mb - the row block size
- nb - the column block size

  Level: intermediate

  Note:
  This block size has a different meaning from the block size associated with `MatSetBlockSize()` used for sparse matrices

.seealso: [](ch_matrices), `Mat`, `MATSCALAPACK`, `MatCreateScaLAPACK()`, `MatScaLAPACKGetBlockSizes()`
@*/
PetscErrorCode MatScaLAPACKSetBlockSizes(Mat A, PetscInt mb, PetscInt nb)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(A, MAT_CLASSID, 1);
  PetscValidLogicalCollectiveInt(A, mb, 2);
  PetscValidLogicalCollectiveInt(A, nb, 3);
  PetscTryMethod(A, "MatScaLAPACKSetBlockSizes_C", (Mat, PetscInt, PetscInt), (A, mb, nb));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode MatScaLAPACKGetBlockSizes_ScaLAPACK(Mat A, PetscInt *mb, PetscInt *nb)
{
  Mat_ScaLAPACK *a = (Mat_ScaLAPACK *)A->data;

  PetscFunctionBegin;
  if (mb) *mb = a->mb;
  if (nb) *nb = a->nb;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  MatScaLAPACKGetBlockSizes - Gets the block sizes used in the distribution of
  the `MATSCALAPACK` matrix

  Not Collective

  Input Parameter:
. A - a `MATSCALAPACK` matrix

  Output Parameters:
+ mb - the row block size
- nb - the column block size

  Level: intermediate

  Note:
  This block size has a different meaning from the block size associated with `MatSetBlockSize()` used for sparse matrices

.seealso: [](ch_matrices), `Mat`, `MATSCALAPACK`, `MatCreateScaLAPACK()`, `MatScaLAPACKSetBlockSizes()`
@*/
PetscErrorCode MatScaLAPACKGetBlockSizes(Mat A, PetscInt *mb, PetscInt *nb)
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(A, MAT_CLASSID, 1);
  PetscUseMethod(A, "MatScaLAPACKGetBlockSizes_C", (Mat, PetscInt *, PetscInt *), (A, mb, nb));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatStashScatterGetMesg_Ref(MatStash *, PetscMPIInt *, PetscInt **, PetscInt **, PetscScalar **, PetscInt *);
PETSC_INTERN PetscErrorCode MatStashScatterEnd_Ref(MatStash *);

/*MC
   MATSCALAPACK = "scalapack" - A matrix type for dense matrices using the ScaLAPACK package

   Use `./configure --download-scalapack` to install PETSc to use ScaLAPACK

   Options Database Keys:
+  -mat_type scalapack - sets the matrix type to `MATSCALAPACK`
.  -pc_factor_mat_solver_type scalapack - to use this direct solver with the option `-pc_type lu`
.  -mat_scalapack_grid_height - sets Grid Height for 2D cyclic ordering of internal matrix
-  -mat_scalapack_block_sizes - size of the blocks to use (one or two integers separated by comma)

   Level: intermediate

  Note:
   Note unlike most matrix formats, this format does not store all the matrix entries for a contiguous
   range of rows on an MPI rank. Use `MatGetOwnershipIS()` to determine what values are stored on
   the given rank.

.seealso: [](ch_matrices), `Mat`, `MATSCALAPACK`, `MATDENSE`, `MATELEMENTAL`, `MatGetOwnershipIS()`, `MatCreateScaLAPACK()`
M*/

PETSC_EXTERN PetscErrorCode MatCreate_ScaLAPACK(Mat A)
{
  Mat_ScaLAPACK      *a;
  PetscBool           flg;
  PetscMPIInt         iflg;
  Mat_ScaLAPACK_Grid *grid;
  MPI_Comm            icomm;
  PetscBLASInt        nprow, npcol, myrow, mycol;
  PetscInt            optv1, k = 2, array[2] = {0, 0};
  PetscMPIInt         size;

  PetscFunctionBegin;
  A->ops[0]     = MatOps_Values;
  A->insertmode = NOT_SET_VALUES;

  PetscCall(MatStashCreate_Private(PetscObjectComm((PetscObject)A), 1, &A->stash));
  A->stash.ScatterBegin   = MatStashScatterBegin_ScaLAPACK;
  A->stash.ScatterGetMesg = MatStashScatterGetMesg_Ref;
  A->stash.ScatterEnd     = MatStashScatterEnd_Ref;
  A->stash.ScatterDestroy = NULL;

  PetscCall(PetscNew(&a));
  A->data = (void *)a;

  /* Grid needs to be shared between multiple Mats on the same communicator, implement by attribute caching on the MPI_Comm */
  if (Petsc_ScaLAPACK_keyval == MPI_KEYVAL_INVALID) {
    PetscCallMPI(MPI_Comm_create_keyval(MPI_COMM_NULL_COPY_FN, MPI_COMM_NULL_DELETE_FN, &Petsc_ScaLAPACK_keyval, NULL));
    PetscCall(PetscRegisterFinalize(Petsc_ScaLAPACK_keyval_free));
    PetscCall(PetscCitationsRegister(ScaLAPACKCitation, &ScaLAPACKCite));
  }
  PetscCall(PetscCommDuplicate(PetscObjectComm((PetscObject)A), &icomm, NULL));
  PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_ScaLAPACK_keyval, (void **)&grid, &iflg));
  if (!iflg) {
    PetscCall(PetscNew(&grid));

    PetscCallMPI(MPI_Comm_size(icomm, &size));
    PetscCall(PetscBLASIntCast(PetscSqrtReal((PetscReal)size) + 0.001, &grid->nprow));

    PetscOptionsBegin(PetscObjectComm((PetscObject)A), ((PetscObject)A)->prefix, "ScaLAPACK Grid Options", "Mat");
    PetscCall(PetscOptionsInt("-mat_scalapack_grid_height", "Grid Height", "None", grid->nprow, &optv1, &flg));
    if (flg) {
      PetscCheck(size % optv1 == 0, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_INCOMP, "Grid Height %" PetscInt_FMT " must evenly divide CommSize %d", optv1, size);
      PetscCall(PetscBLASIntCast(optv1, &grid->nprow));
    }
    PetscOptionsEnd();

    if (size % grid->nprow) grid->nprow = 1; /* cannot use a squarish grid, use a 1d grid */
    grid->npcol = size / grid->nprow;
    PetscCall(PetscBLASIntCast(grid->nprow, &nprow));
    PetscCall(PetscBLASIntCast(grid->npcol, &npcol));
    grid->ictxt = Csys2blacs_handle(icomm);
    Cblacs_gridinit(&grid->ictxt, "R", nprow, npcol);
    Cblacs_gridinfo(grid->ictxt, &nprow, &npcol, &myrow, &mycol);
    grid->grid_refct = 1;
    grid->nprow      = nprow;
    grid->npcol      = npcol;
    grid->myrow      = myrow;
    grid->mycol      = mycol;
    /* auxiliary 1d BLACS contexts for 1xsize and sizex1 grids */
    grid->ictxrow = Csys2blacs_handle(icomm);
    Cblacs_gridinit(&grid->ictxrow, "R", 1, size);
    grid->ictxcol = Csys2blacs_handle(icomm);
    Cblacs_gridinit(&grid->ictxcol, "R", size, 1);
    PetscCallMPI(MPI_Comm_set_attr(icomm, Petsc_ScaLAPACK_keyval, (void *)grid));

  } else grid->grid_refct++;
  PetscCall(PetscCommDestroy(&icomm));
  a->grid = grid;
  a->mb   = DEFAULT_BLOCKSIZE;
  a->nb   = DEFAULT_BLOCKSIZE;

  PetscOptionsBegin(PetscObjectComm((PetscObject)A), NULL, "ScaLAPACK Options", "Mat");
  PetscCall(PetscOptionsIntArray("-mat_scalapack_block_sizes", "Size of the blocks to use (one or two comma-separated integers)", "MatCreateScaLAPACK", array, &k, &flg));
  if (flg) {
    a->mb = (PetscMPIInt)array[0];
    a->nb = (k > 1) ? (PetscMPIInt)array[1] : a->mb;
  }
  PetscOptionsEnd();

  a->roworiented = PETSC_TRUE;
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatGetOwnershipIS_C", MatGetOwnershipIS_ScaLAPACK));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatScaLAPACKSetBlockSizes_C", MatScaLAPACKSetBlockSizes_ScaLAPACK));
  PetscCall(PetscObjectComposeFunction((PetscObject)A, "MatScaLAPACKGetBlockSizes_C", MatScaLAPACKGetBlockSizes_ScaLAPACK));
  PetscCall(PetscObjectChangeTypeName((PetscObject)A, MATSCALAPACK));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  MatCreateScaLAPACK - Creates a dense parallel matrix in ScaLAPACK format
  (2D block cyclic distribution) for a `MATSCALAPACK` matrix

  Collective

  Input Parameters:
+ comm - MPI communicator
. mb   - row block size (or `PETSC_DECIDE` to have it set)
. nb   - column block size (or `PETSC_DECIDE` to have it set)
. M    - number of global rows
. N    - number of global columns
. rsrc - coordinate of process that owns the first row of the distributed matrix
- csrc - coordinate of process that owns the first column of the distributed matrix

  Output Parameter:
. A - the matrix

  Options Database Key:
. -mat_scalapack_block_sizes - size of the blocks to use (one or two integers separated by comma)

  Level: intermediate

  Notes:
  If `PETSC_DECIDE` is used for the block sizes, then an appropriate value is chosen

  It is recommended that one use the `MatCreate()`, `MatSetType()` and/or `MatSetFromOptions()`,
  MatXXXXSetPreallocation() paradigm instead of this routine directly.
  [MatXXXXSetPreallocation() is, for example, `MatSeqAIJSetPreallocation()`]

  Storage is completely managed by ScaLAPACK, so this requires PETSc to be
  configured with ScaLAPACK. In particular, PETSc's local sizes lose
  significance and are thus ignored. The block sizes refer to the values
  used for the distributed matrix, not the same meaning as in `MATBAIJ`.

.seealso: [](ch_matrices), `Mat`, `MATSCALAPACK`, `MATDENSE`, `MATELEMENTAL`, `MatCreate()`, `MatCreateDense()`, `MatSetValues()`
@*/
PetscErrorCode MatCreateScaLAPACK(MPI_Comm comm, PetscInt mb, PetscInt nb, PetscInt M, PetscInt N, PetscInt rsrc, PetscInt csrc, Mat *A)
{
  Mat_ScaLAPACK *a;
  PetscInt       m, n;

  PetscFunctionBegin;
  PetscCall(MatCreate(comm, A));
  PetscCall(MatSetType(*A, MATSCALAPACK));
  PetscCheck(M != PETSC_DECIDE && N != PETSC_DECIDE, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Cannot use PETSC_DECIDE for matrix dimensions");
  /* rows and columns are NOT distributed according to PetscSplitOwnership */
  m = PETSC_DECIDE;
  PetscCall(PetscSplitOwnershipEqual(comm, &m, &M));
  n = PETSC_DECIDE;
  PetscCall(PetscSplitOwnershipEqual(comm, &n, &N));
  PetscCall(MatSetSizes(*A, m, n, M, N));
  a = (Mat_ScaLAPACK *)(*A)->data;
  PetscCall(PetscBLASIntCast(M, &a->M));
  PetscCall(PetscBLASIntCast(N, &a->N));
  PetscCall(PetscBLASIntCast((mb == PETSC_DECIDE) ? DEFAULT_BLOCKSIZE : mb, &a->mb));
  PetscCall(PetscBLASIntCast((nb == PETSC_DECIDE) ? a->mb : nb, &a->nb));
  PetscCall(PetscBLASIntCast(rsrc, &a->rsrc));
  PetscCall(PetscBLASIntCast(csrc, &a->csrc));
  PetscCall(MatSetUp(*A));
  PetscFunctionReturn(PETSC_SUCCESS);
}