static char help[] = "Tests MatOption MAT_FORCE_DIAGONAL_ENTRIES.\n\n";

#include <petscmat.h>

int main(int argc,char **args)
{
  Mat            A,B;
  Vec            diag;
  PetscInt       i,n = 10,col[3],test;
  PetscErrorCode ierr;
  PetscScalar    v[3];

  ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
  ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);

  /* Create A which has empty 0-th row and column */
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetType(A,MATAIJ);CHKERRQ(ierr);
  ierr = MatSetFromOptions(A);CHKERRQ(ierr);
  ierr = MatSetUp(A);CHKERRQ(ierr);

  v[0] = -1.; v[1] = 2.; v[2] = -1.;
  for (i=2; i<n-1; i++) {
    col[0] = i-1; col[1] = i; col[2] = i+1;
    ierr = MatSetValues(A,1,&i,3,col,v,INSERT_VALUES);CHKERRQ(ierr);
  }
  i    = 1; col[0] = 1; col[1] = 2;
  ierr = MatSetValues(A,1,&i,2,col,v+1,INSERT_VALUES);CHKERRQ(ierr);
  i    = n - 1; col[0] = n - 2; col[1] = n - 1;
  ierr = MatSetValues(A,1,&i,2,col,v,INSERT_VALUES);CHKERRQ(ierr);
  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  for (test = 0; test < 2; test++) {
    ierr = MatProductCreate(A,A,NULL,&B);CHKERRQ(ierr);

    if (test == 0) {
      /* Compute B = A*A; B misses 0-th diagonal */
      ierr = MatProductSetType(B,MATPRODUCT_AB);CHKERRQ(ierr);
    } else {
      /* Compute B = A^t*A; B misses 0-th diagonal */
      ierr = MatProductSetType(B,MATPRODUCT_AtB);CHKERRQ(ierr);
    }

    /* Force allocate missing diagonal entries of B */
    ierr = MatSetOption(B,MAT_FORCE_DIAGONAL_ENTRIES,PETSC_TRUE);CHKERRQ(ierr);
    ierr = MatProductSetFromOptions(B);CHKERRQ(ierr);

    ierr = MatProductSymbolic(B);CHKERRQ(ierr);
    ierr = MatProductNumeric(B);CHKERRQ(ierr);

    ierr = MatSetOption(B,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE);CHKERRQ(ierr);

    /* Insert entries to diagonal of B */
    ierr = MatCreateVecs(B,NULL,&diag);CHKERRQ(ierr);
    ierr = MatGetDiagonal(B,diag);CHKERRQ(ierr);
    ierr = VecSetValue(diag,0,100.0,INSERT_VALUES);CHKERRQ(ierr);
    ierr = VecAssemblyBegin(diag);CHKERRQ(ierr);
    ierr = VecAssemblyEnd(diag);CHKERRQ(ierr);

    ierr = MatDiagonalSet(B,diag,INSERT_VALUES);CHKERRQ(ierr);
    if (test == 1) {
      ierr = MatView(B,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
    }
    ierr = MatDestroy(&B);CHKERRQ(ierr);
    ierr = VecDestroy(&diag);CHKERRQ(ierr);
  }

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

/*TEST

   test:
     output_file: output/ex81_1.out

   test:
     suffix: 2
     args: -matproduct_atb_via at*b
     output_file: output/ex81_1.out

   test:
     suffix: 3
     args: -matproduct_atb_via outerproduct
     output_file: output/ex81_1.out

   test:
     suffix: 4
     nsize: 3
     args: -matproduct_atb_via nonscalable
     output_file: output/ex81_3.out

   test:
     suffix: 5
     nsize: 3
     args: -matproduct_atb_via scalable
     output_file: output/ex81_3.out

   test:
     suffix: 6
     nsize: 3
     args: -matproduct_atb_via at*b
     output_file: output/ex81_3.out

TEST*/