static char help[] = "Tests repeated use of assembly for matrices.\n\n";

#include <petscmat.h>

int main(int argc,char **args)
{
  Mat            C;
  PetscInt       i,j,m = 5,n = 2,Ii,J;
  PetscErrorCode ierr;
  PetscMPIInt    rank,size;
  PetscScalar    v;

  ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
  CHKERRMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));
  CHKERRMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size));
  n    = 2*size;

  /* create the matrix for the five point stencil, YET AGAIN*/
  CHKERRQ(MatCreate(PETSC_COMM_WORLD,&C));
  CHKERRQ(MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n));
  CHKERRQ(MatSetFromOptions(C));
  CHKERRQ(MatSetUp(C));
  for (i=0; i<m; i++) {
    for (j=2*rank; j<2*rank+2; j++) {
      v = -1.0;  Ii = j + n*i;
      if (i>0)   {J = Ii - n; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (i<m-1) {J = Ii + n; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (j>0)   {J = Ii - 1; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (j<n-1) {J = Ii + 1; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      v = 4.0; CHKERRQ(MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES));
    }
  }
  CHKERRQ(MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY));
  CHKERRQ(MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY));
  for (i=0; i<m; i++) {
    for (j=2*rank; j<2*rank+2; j++) {
      v = 1.0;  Ii = j + n*i;
      if (i>0)   {J = Ii - n; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (i<m-1) {J = Ii + n; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (j>0)   {J = Ii - 1; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      if (j<n-1) {J = Ii + 1; CHKERRQ(MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES));}
      v = -4.0; CHKERRQ(MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES));
    }
  }
  CHKERRQ(MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY));
  CHKERRQ(MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY));

  CHKERRQ(MatView(C,PETSC_VIEWER_STDOUT_WORLD));

  CHKERRQ(MatDestroy(&C));
  ierr = PetscFinalize();
  return ierr;
}

/*TEST

   test:

TEST*/