static char help[] = "Reads a PETSc matrix and computes the 2 norm of the columns\n\n";

/*
  Include "petscmat.h" so that we can use matrices.
  automatically includes:
     petscsys.h       - base PETSc routines   petscvec.h    - vectors
     petscmat.h    - matrices
     petscis.h     - index sets            petscviewer.h - viewers
*/
#include <petscmat.h>

int main(int argc, char **args)
{
  Mat               A;                        /* matrix */
  PetscViewer       fd;                       /* viewer */
  char              file[PETSC_MAX_PATH_LEN]; /* input file name */
  PetscReal        *norms;
  PetscInt          n, cstart, cend;
  PetscBool         flg;
  PetscViewerFormat format;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  /*
     Determine files from which we read the matrix
  */
  PetscCall(PetscOptionsGetString(NULL, NULL, "-f", file, sizeof(file), &flg));
  PetscCheck(flg, PETSC_COMM_WORLD, PETSC_ERR_USER, "Must indicate binary file with the -f option");

  /*
     Open binary file.  Note that we use FILE_MODE_READ to indicate
     reading from this file.
  */
  PetscCall(PetscViewerCreate(PETSC_COMM_WORLD, &fd));
  PetscCall(PetscViewerSetType(fd, PETSCVIEWERBINARY));
  PetscCall(PetscViewerSetFromOptions(fd));
  PetscCall(PetscOptionsGetEnum(NULL, NULL, "-viewer_format", PetscViewerFormats, (PetscEnum *)&format, &flg));
  if (flg) PetscCall(PetscViewerPushFormat(fd, format));
  PetscCall(PetscViewerFileSetMode(fd, FILE_MODE_READ));
  PetscCall(PetscViewerFileSetName(fd, file));

  /*
    Load the matrix; then destroy the viewer.
    Matrix type is set automatically but you can override it by MatSetType() prior to MatLoad().
    Do that only if you really insist on the given type.
  */
  PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
  PetscCall(MatSetOptionsPrefix(A, "a_"));
  PetscCall(PetscObjectSetName((PetscObject)A, "A"));
  PetscCall(MatSetFromOptions(A));
  PetscCall(MatLoad(A, fd));
  PetscCall(PetscViewerDestroy(&fd));

  PetscCall(MatGetSize(A, NULL, &n));
  PetscCall(MatGetOwnershipRangeColumn(A, &cstart, &cend));
  PetscCall(PetscMalloc1(n, &norms));
  PetscCall(MatGetColumnNorms(A, NORM_2, norms));
  PetscCall(PetscRealView(cend - cstart, norms + cstart, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(PetscFree(norms));

  PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)A, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(MatViewFromOptions(A, NULL, "-mat_view"));

  PetscCall(MatDestroy(&A));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      suffix: mpiaij
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
      args: -f ${DATAFILESPATH}/matrices/small -a_mat_type mpiaij
      args: -a_matload_symmetric

   test:
      suffix: mpiaij_hdf5
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small.mat -a_mat_type mpiaij -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      suffix: mpiaij_rect_hdf5
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_rect.mat -a_mat_type mpiaij -viewer_type hdf5 -viewer_format hdf5_mat

   test:
      # test for more processes than rows
      suffix: mpiaij_hdf5_tiny
      nsize: 8
      requires: double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${wPETSC_DIR}/share/petsc/datafiles/matrices/tiny_system_with_x0.mat -a_mat_type mpiaij -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      # test for more processes than rows, complex
      TODO: not yet implemented for MATLAB complex format
      suffix: mpiaij_hdf5_tiny_complex
      nsize: 8
      requires: double complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${wPETSC_DIR}/share/petsc/datafiles/matrices/tiny_system_with_x0_complex.mat -a_mat_type mpiaij -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      TODO: mpibaij not supported yet
      suffix: mpibaij_hdf5
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small.mat -a_mat_type mpibaij -a_mat_block_size 2 -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      suffix: mpidense
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
      args: -f ${DATAFILESPATH}/matrices/small -a_mat_type mpidense
      args: -a_matload_symmetric

   test:
      suffix: seqaij
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
      args: -f ${DATAFILESPATH}/matrices/small -a_mat_type seqaij
      args: -a_matload_symmetric

   test:
      suffix: seqaij_hdf5
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small.mat -a_mat_type seqaij -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      suffix: seqaij_rect_hdf5
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_rect.mat -a_mat_type seqaij -viewer_type hdf5 -viewer_format hdf5_mat

   test:
      suffix: seqdense
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
      args: -f ${DATAFILESPATH}/matrices/small -a_mat_type seqdense
      args: -a_matload_symmetric

   test:
      suffix: seqdense_hdf5
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_dense.mat -a_mat_type seqdense -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      suffix: seqdense_rect_hdf5
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_rect_dense.mat -a_mat_type seqdense -viewer_type hdf5 -viewer_format hdf5_mat

   test:
      suffix: mpidense_hdf5
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_dense.mat -a_mat_type mpidense -viewer_type hdf5 -viewer_format hdf5_mat
      args: -a_matload_symmetric

   test:
      suffix: mpidense_rect_hdf5
      nsize: 2
      requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES) hdf5 defined(PETSC_HDF5_HAVE_ZLIB)
      args: -f ${DATAFILESPATH}/matrices/matlab/small_rect_dense.mat -a_mat_type mpidense -viewer_type hdf5 -viewer_format hdf5_mat
TEST*/