static char help[] = "Test MatMatMatMult\n\
Reads PETSc matrix A B and C, then comput D=A*B*C \n\
Input parameters include\n\
  -fA <input_file> -fB <input_file> -fC <input_file> \n\n";

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat         A, B, C, D, BC, ABC;
  PetscViewer fd;
  char        file[3][PETSC_MAX_PATH_LEN];
  PetscBool   flg;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  /* read matrices A, B and C */
  PetscCall(PetscOptionsGetString(NULL, NULL, "-fA", file[0], sizeof(file[0]), &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_USER, "Must indicate binary file with the -fA options");

  PetscCall(PetscOptionsGetString(NULL, NULL, "-fB", file[1], sizeof(file[1]), &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_USER, "Must indicate binary file with the -fB options");

  PetscCall(PetscOptionsGetString(NULL, NULL, "-fC", file[2], sizeof(file[2]), &flg));
  PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_USER, "Must indicate binary file with the -fC options");

  /* Load matrices */
  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file[0], FILE_MODE_READ, &fd));
  PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
  PetscCall(MatLoad(A, fd));
  PetscCall(PetscViewerDestroy(&fd));

  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file[1], FILE_MODE_READ, &fd));
  PetscCall(MatCreate(PETSC_COMM_WORLD, &B));
  PetscCall(MatLoad(B, fd));
  PetscCall(PetscViewerDestroy(&fd));

  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file[2], FILE_MODE_READ, &fd));
  PetscCall(MatCreate(PETSC_COMM_WORLD, &C));
  PetscCall(MatLoad(C, fd));
  PetscCall(PetscViewerDestroy(&fd));

  /* Test MatMatMult() */
  PetscCall(MatMatMult(B, C, MAT_INITIAL_MATRIX, PETSC_DETERMINE, &BC));
  PetscCall(MatMatMult(A, BC, MAT_INITIAL_MATRIX, PETSC_DETERMINE, &ABC));

  PetscCall(MatMatMatMult(A, B, C, MAT_INITIAL_MATRIX, PETSC_DETERMINE, &D));
  PetscCall(MatMatMatMult(A, B, C, MAT_REUSE_MATRIX, PETSC_DETERMINE, &D));
  /* PetscCall(MatView(D,PETSC_VIEWER_STDOUT_WORLD)); */

  PetscCall(MatEqual(ABC, D, &flg));
  PetscCheck(flg, PetscObjectComm((PetscObject)A), PETSC_ERR_ARG_INCOMP, "ABC != D");

  PetscCall(MatDestroy(&ABC));
  PetscCall(MatDestroy(&BC));
  PetscCall(MatDestroy(&D));
  PetscCall(MatDestroy(&C));
  PetscCall(MatDestroy(&B));
  PetscCall(MatDestroy(&A));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      requires: datafilespath !complex double !defined(PETSC_USE_64BIT_INDICES)
      args: -fA ${DATAFILESPATH}/matrices/matmatmatmult/A.bin -fB ${DATAFILESPATH}/matrices/matmatmatmult/B.bin -fC ${DATAFILESPATH}/matrices/matmatmatmult/C.bin
      output_file: output/empty.out

   test:
      suffix: 2
      nsize: 3
      requires: datafilespath !complex double !defined(PETSC_USE_64BIT_INDICES)
      args: -fA ${DATAFILESPATH}/matrices/matmatmatmult/A.bin -fB ${DATAFILESPATH}/matrices/matmatmatmult/B.bin -fC ${DATAFILESPATH}/matrices/matmatmatmult/C.bin
      output_file: output/empty.out

TEST*/