static char help[] = "Test interface of Elemental. \n\n";

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat             C, Caij;
  PetscInt        i, j, m = 5, n, nrows, ncols;
  const PetscInt *rows, *cols;
  IS              isrows, iscols;
  PetscBool       flg, Test_MatMatMult = PETSC_FALSE, mats_view = PETSC_FALSE;
  PetscScalar    *v;
  PetscMPIInt     rank, size;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  PetscCall(PetscOptionsHasName(NULL, NULL, "-mats_view", &mats_view));

  /* Get local block or element size*/
  PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
  n = m;
  PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

  PetscCall(MatCreate(PETSC_COMM_WORLD, &C));
  PetscCall(MatSetSizes(C, m, n, PETSC_DECIDE, PETSC_DECIDE));
  PetscCall(MatSetType(C, MATELEMENTAL));
  PetscCall(MatSetFromOptions(C));
  PetscCall(MatSetUp(C));

  PetscCall(PetscOptionsHasName(NULL, NULL, "-row_oriented", &flg));
  if (flg) PetscCall(MatSetOption(C, MAT_ROW_ORIENTED, PETSC_TRUE));
  PetscCall(MatGetOwnershipIS(C, &isrows, &iscols));
  PetscCall(PetscOptionsHasName(NULL, NULL, "-Cexp_view_ownership", &flg));
  if (flg) { /* View ownership of explicit C */
    IS tmp;
    PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Ownership of explicit C:\n"));
    PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Row index set:\n"));
    PetscCall(ISOnComm(isrows, PETSC_COMM_WORLD, PETSC_USE_POINTER, &tmp));
    PetscCall(ISView(tmp, PETSC_VIEWER_STDOUT_WORLD));
    PetscCall(ISDestroy(&tmp));
    PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Column index set:\n"));
    PetscCall(ISOnComm(iscols, PETSC_COMM_WORLD, PETSC_USE_POINTER, &tmp));
    PetscCall(ISView(tmp, PETSC_VIEWER_STDOUT_WORLD));
    PetscCall(ISDestroy(&tmp));
  }

  /* Set local matrix entries */
  PetscCall(ISGetLocalSize(isrows, &nrows));
  PetscCall(ISGetIndices(isrows, &rows));
  PetscCall(ISGetLocalSize(iscols, &ncols));
  PetscCall(ISGetIndices(iscols, &cols));
  PetscCall(PetscMalloc1(nrows * ncols, &v));
  for (i = 0; i < nrows; i++) {
    for (j = 0; j < ncols; j++) {
      /*v[i*ncols+j] = (PetscReal)rank;*/
      v[i * ncols + j] = (PetscReal)(rank * 10000 + 100 * rows[i] + cols[j]);
    }
  }
  PetscCall(MatSetValues(C, nrows, rows, ncols, cols, v, INSERT_VALUES));
  PetscCall(ISRestoreIndices(isrows, &rows));
  PetscCall(ISRestoreIndices(iscols, &cols));
  PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));

  /* Test MatView() */
  if (mats_view) PetscCall(MatView(C, PETSC_VIEWER_STDOUT_WORLD));

  /* Set unowned matrix entries - add subdiagonals and diagonals from proc[0] */
  if (rank == 0) {
    PetscInt M, N, cols[2];
    PetscCall(MatGetSize(C, &M, &N));
    for (i = 0; i < M; i++) {
      cols[0] = i;
      v[0]    = i + 0.5;
      cols[1] = i - 1;
      v[1]    = 0.5;
      if (i) {
        PetscCall(MatSetValues(C, 1, &i, 2, cols, v, ADD_VALUES));
      } else {
        PetscCall(MatSetValues(C, 1, &i, 1, &i, v, ADD_VALUES));
      }
    }
  }
  PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));

  /* Test MatMult() */
  PetscCall(MatComputeOperator(C, MATAIJ, &Caij));
  PetscCall(MatMultEqual(C, Caij, 5, &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_NOTSAMETYPE, "C != Caij. MatMultEqual() fails");
  PetscCall(MatMultTransposeEqual(C, Caij, 5, &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_NOTSAMETYPE, "C != Caij. MatMultTransposeEqual() fails");

  /* Test MatMultAdd() and MatMultTransposeAddEqual() */
  PetscCall(MatMultAddEqual(C, Caij, 5, &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_NOTSAMETYPE, "C != Caij. MatMultAddEqual() fails");
  PetscCall(MatMultTransposeAddEqual(C, Caij, 5, &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_NOTSAMETYPE, "C != Caij. MatMultTransposeAddEqual() fails");

  /* Test MatMatMult() */
  PetscCall(PetscOptionsHasName(NULL, NULL, "-test_matmatmult", &Test_MatMatMult));
  if (Test_MatMatMult) {
    Mat CCelem, CCaij;
    PetscCall(MatMatMult(C, C, MAT_INITIAL_MATRIX, PETSC_DETERMINE, &CCelem));
    PetscCall(MatMatMult(Caij, Caij, MAT_INITIAL_MATRIX, PETSC_DETERMINE, &CCaij));
    PetscCall(MatMultEqual(CCelem, CCaij, 5, &flg));
    PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_NOTSAMETYPE, "CCelem != CCaij. MatMatMult() fails");
    PetscCall(MatDestroy(&CCaij));
    PetscCall(MatDestroy(&CCelem));
  }

  PetscCall(PetscFree(v));
  PetscCall(ISDestroy(&isrows));
  PetscCall(ISDestroy(&iscols));
  PetscCall(MatDestroy(&C));
  PetscCall(MatDestroy(&Caij));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      nsize: 2
      requires: elemental
      args: -mat_type elemental -m 2 -n 3
      output_file: output/empty.out

   test:
      suffix: 2
      nsize: 6
      requires: elemental
      args: -mat_type elemental -m 2 -n 2
      output_file: output/empty.out

   test:
      suffix: 3
      nsize: 6
      requires: elemental
      args: -mat_type elemental -m 2 -n 2 -test_matmatmult
      output_file: output/empty.out

TEST*/