static char help[]= "Test VecScatterCreateToZero, VecScatterCreateToAll\n\n";

#include <petscvec.h>
int main(int argc,char **argv)
{
  PetscErrorCode     ierr;
  PetscInt           i,N=10,low,high;
  PetscMPIInt        size,rank;
  Vec                x,y;
  VecScatter         vscat;

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

  ierr = VecCreate(PETSC_COMM_WORLD,&x);CHKERRQ(ierr);
  ierr = VecSetFromOptions(x);CHKERRQ(ierr);
  ierr = VecSetSizes(x,PETSC_DECIDE,N);CHKERRQ(ierr);
  ierr = VecGetOwnershipRange(x,&low,&high);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject)x,"x");CHKERRQ(ierr);

  /*-------------------------------------*/
  /*       VecScatterCreateToZero        */
  /*-------------------------------------*/

  /* MPI vec x = [0, 1, 2, .., N-1] */
  for (i=low; i<high; i++) {ierr = VecSetValue(x,i,(PetscScalar)i,INSERT_VALUES);CHKERRQ(ierr);}
  ierr = VecAssemblyBegin(x);CHKERRQ(ierr);
  ierr = VecAssemblyEnd(x);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD,"\nTesting VecScatterCreateToZero\n");CHKERRQ(ierr);
  ierr = VecScatterCreateToZero(x,&vscat,&y);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject)y,"y");CHKERRQ(ierr);

  /* Test PetscSFBcastAndOp with op = MPI_REPLACE, which does y = x on rank 0 */
  ierr = VecScatterBegin(vscat,x,y,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,x,y,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  if (rank == 0) {ierr = VecView(y,PETSC_VIEWER_STDOUT_SELF);CHKERRQ(ierr);}

  /* Test PetscSFBcastAndOp with op = MPI_SUM, which does y += x */
  ierr = VecScatterBegin(vscat,x,y,ADD_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,x,y,ADD_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  if (rank == 0) {ierr = VecView(y,PETSC_VIEWER_STDOUT_SELF);CHKERRQ(ierr);}

  /* Test PetscSFReduce with op = MPI_REPLACE, which does x = y */
  ierr = VecScatterBegin(vscat,y,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,y,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecView(x,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);

  /* Test PetscSFReduce with op = MPI_SUM, which does x += y on x's local part on rank 0*/
  ierr = VecScatterBegin(vscat,y,x,ADD_VALUES,SCATTER_REVERSE_LOCAL);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,y,x,ADD_VALUES,SCATTER_REVERSE_LOCAL);CHKERRQ(ierr);
  ierr = VecView(x,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);

  ierr = VecDestroy(&y);CHKERRQ(ierr);
  ierr = VecScatterDestroy(&vscat);CHKERRQ(ierr);

  /*-------------------------------------*/
  /*       VecScatterCreateToAll         */
  /*-------------------------------------*/
  for (i=low; i<high; i++) {ierr = VecSetValue(x,i,(PetscScalar)i,INSERT_VALUES);CHKERRQ(ierr);}
  ierr = VecAssemblyBegin(x);CHKERRQ(ierr);
  ierr = VecAssemblyEnd(x);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD,"\nTesting VecScatterCreateToAll\n");CHKERRQ(ierr);

  ierr = VecScatterCreateToAll(x,&vscat,&y);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject)y,"y");CHKERRQ(ierr);

  /* Test PetscSFBcastAndOp with op = MPI_REPLACE, which does y = x on all ranks */
  ierr = VecScatterBegin(vscat,x,y,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,x,y,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  if (rank == 0) {ierr = VecView(y,PETSC_VIEWER_STDOUT_SELF);CHKERRQ(ierr);}

  /* Test PetscSFBcastAndOp with op = MPI_SUM, which does y += x */
  ierr = VecScatterBegin(vscat,x,y,ADD_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,x,y,ADD_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
  if (rank == 0) {ierr = VecView(y,PETSC_VIEWER_STDOUT_SELF);CHKERRQ(ierr);}

  /* Test PetscSFReduce with op = MPI_REPLACE, which does x = y */
  ierr = VecScatterBegin(vscat,y,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,y,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecView(x,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);

  /* Test PetscSFReduce with op = MPI_SUM, which does x += size*y */
  ierr = VecScatterBegin(vscat,y,x,ADD_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecScatterEnd(vscat,y,x,ADD_VALUES,SCATTER_REVERSE);CHKERRQ(ierr);
  ierr = VecView(x,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
  ierr = VecDestroy(&x);CHKERRQ(ierr);
  ierr = VecDestroy(&y);CHKERRQ(ierr);
  ierr = VecScatterDestroy(&vscat);CHKERRQ(ierr);

  ierr = PetscFinalize();
  return ierr;
}

/*TEST

   testset:
      # N=10 is divisible by nsize, to trigger Allgather/Gather in SF
      nsize: 2
      # Exact numbers really matter here
      diff_args: -j
      filter: grep -v "type"
      output_file: output/ex8_1.out

      test:
        suffix: 1_standard

      test:
        suffix: 1_cuda
        # sf_backend cuda is not needed if compiling only with cuda
        args: -vec_type cuda -sf_backend cuda -vecscatter_packongpu true
        requires: cuda

      test:
        suffix: 1_hip
        args: -vec_type hip -sf_backend hip -vecscatter_packongpu true
        requires: hip

      test:
        suffix: 1_cuda_aware_mpi
        # sf_backend cuda is not needed if compiling only with cuda
        args: -vec_type cuda -sf_backend cuda -vecscatter_packongpu false
        requires: cuda defined(PETSC_HAVE_MPI_GPU_AWARE)

   testset:
      # N=10 is not divisible by nsize, to trigger Allgatherv/Gatherv in SF
      nsize: 3
      # Exact numbers really matter here
      diff_args: -j
      filter: grep -v "type"
      output_file: output/ex8_2.out

      test:
        suffix: 2_standard

      test:
        suffix: 2_cuda
        # sf_backend cuda is not needed if compiling only with cuda
        args: -vec_type cuda -sf_backend cuda -vecscatter_packongpu true
        requires: cuda

      test:
        suffix: 2_hip
        # sf_backend hip is not needed if compiling only with hip
        args: -vec_type hip -sf_backend hip -vecscatter_packongpu true
        requires: hip

      test:
        suffix: 2_cuda_aware_mpi
        args: -vec_type cuda -vecscatter_packongpu false
        requires: cuda defined(PETSC_HAVE_MPI_GPU_AWARE)

TEST*/