static char help[] = "Saves a rectangular sparse matrix to disk.\n\n";

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat         A;
  PetscInt    m = 100, n = 11, js[11], i, j, cnt;
  PetscScalar values[11];
  PetscViewer view;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCall(MatCreateSeqAIJ(PETSC_COMM_WORLD, m, n, 20, 0, &A));

  for (i = 0; i < n; i++) values[i] = (PetscReal)i;

  for (i = 0; i < m; i++) {
    cnt = 0;
    if (i % 2) {
      for (j = 0; j < n; j += 2) js[cnt++] = j;
    }
    PetscCall(MatSetValues(A, 1, &i, cnt, js, values, INSERT_VALUES));
  }
  PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));

  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, "rect", FILE_MODE_WRITE, &view));
  PetscCall(MatView(A, view));
  PetscCall(PetscViewerDestroy(&view));

  PetscCall(MatDestroy(&A));

  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
     output_file: output/empty.out

TEST*/