[petsc-dev] Problem with l2g IS created by VecCreateGhostBlock

[Garth Wells]

I'm seeing an issue because I previously built my own l2g IS, whereas
now I'm relying on the IS created by VecCreateGhostBlock.

For a vector with 8 entries and block size 2 (i.e, 4 blocks), and
arranged:

P0: Owns blocks: 0
    Ghost blocks: 1, 2 

P1: Owns blocks: 1, 2, 3
    Ghost blocks: None

I expected the local-to-global IS created by VecCreateGhostBlock on
proc 1 to be:

0  1
1  2
2  3

But I get 

0  2  
1  3
2  4

The below code illustrates (run with 2 procs). I'm using the dev master
branch (updated just now).

Am I doing something wrong?

Garth



#include <petsc.h>
static char help[] = "Test ghost vec";
int main(int argc, char **argv)
{
  PetscInitialize(&argc, &argv, (char *)0, help);

  PetscMPIInt rank;
  MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

  Vec x;
  if (rank == 0)
  {
    PetscInt ghst[2] = {1, 2};
    VecCreateGhostBlock(PETSC_COMM_WORLD, 2, 2, PETSC_DECIDE, 2, ghst,
&x);
  }
  else if (rank == 1)
  {
    VecCreateGhostBlock(PETSC_COMM_WORLD, 2, 6, PETSC_DECIDE, 0, NULL,
&x);

    ISLocalToGlobalMapping mapping;
    VecGetLocalToGlobalMapping(x, &mapping);
    ISLocalToGlobalMappingView(mapping, PETSC_VIEWER_STDOUT_SELF);
  }
  return 0;
}