static char help[] = "Tests converting a SBAIJ matrix to BAIJ format with MatConvert. Modified from ex55.c\n\n";

#include <petscmat.h>
/* Usage: ./ex141 -mat_view */

int main(int argc, char **args)
{
  Mat         C, B;
  PetscInt    i, bs = 2, mbs, m, block, d_nz = 6, col[3];
  PetscMPIInt size;
  char        file[PETSC_MAX_PATH_LEN];
  PetscViewer fd;
  PetscBool   equal, loadmat;
  PetscScalar value[4];
  PetscInt    ridx[2], cidx[2];

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCall(PetscOptionsGetString(NULL, NULL, "-f", file, sizeof(file), &loadmat));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!");

  /* input matrix C */
  if (loadmat) {
    /* Open binary file. Load a sbaij matrix, then destroy the viewer. */
    PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file, FILE_MODE_READ, &fd));
    PetscCall(MatCreate(PETSC_COMM_WORLD, &C));
    PetscCall(MatSetType(C, MATSEQSBAIJ));
    PetscCall(MatLoad(C, fd));
    PetscCall(PetscViewerDestroy(&fd));
  } else { /* Create a sbaij mat with bs>1  */
    mbs = 8;
    PetscCall(PetscOptionsGetInt(NULL, NULL, "-mbs", &mbs, NULL));
    m = mbs * bs;
    PetscCall(MatCreate(PETSC_COMM_WORLD, &C));
    PetscCall(MatSetSizes(C, PETSC_DECIDE, PETSC_DECIDE, m, m));
    PetscCall(MatSetType(C, MATSBAIJ));
    PetscCall(MatSetFromOptions(C));
    PetscCall(MatSeqSBAIJSetPreallocation(C, bs, d_nz, NULL));
    PetscCall(MatSetUp(C));
    PetscCall(MatSetOption(C, MAT_IGNORE_LOWER_TRIANGULAR, PETSC_TRUE));

    for (block = 0; block < mbs; block++) {
      /* diagonal blocks */
      value[0] = -1.0;
      value[1] = 4.0;
      value[2] = -1.0;
      for (i = 1 + block * bs; i < bs - 1 + block * bs; i++) {
        col[0] = i - 1;
        col[1] = i;
        col[2] = i + 1;
        PetscCall(MatSetValues(C, 1, &i, 3, col, value, INSERT_VALUES));
      }
      i      = bs - 1 + block * bs;
      col[0] = bs - 2 + block * bs;
      col[1] = bs - 1 + block * bs;

      value[0] = -1.0;
      value[1] = 4.0;
      PetscCall(MatSetValues(C, 1, &i, 2, col, value, INSERT_VALUES));

      i      = 0 + block * bs;
      col[0] = 0 + block * bs;
      col[1] = 1 + block * bs;

      value[0] = 4.0;
      value[1] = -1.0;
      PetscCall(MatSetValues(C, 1, &i, 2, col, value, INSERT_VALUES));
    }
    /* off-diagonal blocks */
    value[0] = -1.0;
    value[1] = -0.1;
    value[2] = 0.0;
    value[3] = -1.0; /* row-oriented */
    for (block = 0; block < mbs - 1; block++) {
      for (i = 0; i < bs; i++) {
        ridx[i] = block * bs + i;
        cidx[i] = (block + 1) * bs + i;
      }
      PetscCall(MatSetValues(C, bs, ridx, bs, cidx, value, INSERT_VALUES));
    }
    PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
  }

  /* convert C to BAIJ format */
  PetscCall(MatConvert(C, MATSEQBAIJ, MAT_INITIAL_MATRIX, &B));
  PetscCall(MatMultEqual(B, C, 10, &equal));
  PetscCheck(equal, PETSC_COMM_SELF, PETSC_ERR_PLIB, "MatConvert fails!");

  PetscCall(MatDestroy(&B));
  PetscCall(MatDestroy(&C));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
     output_file: output/empty.out

TEST*/