static char help[] = "Demonstrates using PetscViewerPushFormat(viewer,PETSC_VIEWER_BINARY_MATLAB)\n\n";

#include <petscsys.h>
#include <petscdm.h>
#include <petscdmda.h>
#include <petscbag.h>

typedef struct {
  char      filename[PETSC_MAX_PATH_LEN];
  PetscReal ra;
  PetscInt  ia;
  PetscBool ta;
} Parameter;

int main(int argc, char **argv)
{
  PetscBag    bag;
  Parameter  *params;
  PetscViewer viewer;
  DM          da;
  Vec         global, local;
  PetscMPIInt rank;

  /*
    Every PETSc routine should begin with the PetscInitialize() routine.
    argc, argv - These command line arguments are taken to extract the options
                 supplied to PETSc and options supplied to MPI.
    help       - When PETSc executable is invoked with the option -help,
                 it prints the various options that can be applied at
                 runtime.  The user can use the "help" variable place
                 additional help messages in this printout.
  */
  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  /* Create a DMDA and an associated vector */
  PetscCall(DMDACreate2d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DMDA_STENCIL_BOX, 10, 10, PETSC_DECIDE, PETSC_DECIDE, 2, 1, NULL, NULL, &da));
  PetscCall(DMSetFromOptions(da));
  PetscCall(DMSetUp(da));
  PetscCall(DMCreateGlobalVector(da, &global));
  PetscCall(DMCreateLocalVector(da, &local));
  PetscCall(VecSet(global, -1.0));
  PetscCall(DMGlobalToLocalBegin(da, global, INSERT_VALUES, local));
  PetscCall(DMGlobalToLocalEnd(da, global, INSERT_VALUES, local));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
  PetscCall(VecScale(local, rank + 1));
  PetscCall(DMLocalToGlobalBegin(da, local, ADD_VALUES, global));
  PetscCall(DMLocalToGlobalEnd(da, local, ADD_VALUES, global));

  /* Create an empty bag */
  PetscCall(PetscBagCreate(PETSC_COMM_WORLD, sizeof(Parameter), &bag));
  PetscCall(PetscBagGetData(bag, &params));

  /* fill bag: register variables, defaults, names, help strings */
  PetscCall(PetscBagSetName(bag, "ParameterBag", "contains problem parameters"));
  PetscCall(PetscBagRegisterString(bag, &params->filename, PETSC_MAX_PATH_LEN, "output_file", "filename", "Name of secret file"));
  PetscCall(PetscBagRegisterReal(bag, &params->ra, 1.0, "param_1", "The first parameter"));
  PetscCall(PetscBagRegisterInt(bag, &params->ia, 5, "param_2", "The second parameter"));
  PetscCall(PetscBagRegisterBool(bag, &params->ta, PETSC_TRUE, "do_output", "Write output file (true/false)"));

  /*
     Write output file with PETSC_VIEWER_BINARY_MATLAB format
     NOTE: the output generated with this viewer can be loaded into
     MATLAB using $PETSC_DIR/share/petsc/matlab/PetscReadBinaryMatlab.m
  */
  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, params->filename, FILE_MODE_WRITE, &viewer));
  PetscCall(PetscViewerPushFormat(viewer, PETSC_VIEWER_BINARY_MATLAB));
  PetscCall(PetscBagView(bag, viewer));
  PetscCall(DMDASetFieldName(da, 0, "field1"));
  PetscCall(DMDASetFieldName(da, 1, "field2"));
  PetscCall(PetscObjectSetName((PetscObject)global, "da1"));
  PetscCall(VecView(global, viewer));
  PetscCall(PetscViewerPopFormat(viewer));
  PetscCall(PetscViewerDestroy(&viewer));

  /* clean up and exit */
  PetscCall(PetscBagDestroy(&bag));
  PetscCall(DMDestroy(&da));
  PetscCall(VecDestroy(&local));
  PetscCall(VecDestroy(&global));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
     output_file: output/empty.out

TEST*/
