[mpich-discuss] rank ordering from MPI_Cart_create

[Kokron, Daniel S. (GSFC-610.1)[Computer Sciences Corporation]]

I am attempting to convert an existing application to use the new MPI_Neighbor_* routines for halo updates.  The trouble I'm having is that the application fixes the ranks in a right-handed cartesian grid while that produced by MPI_Cart_create appears to be left-handed.

MPI_Cart_create produces a rank ordering for a 4x4 grid
  0   1    2   3
  4   5    6   7
  8   9  10 11
12 13 14 15

The application expects the ranks to be ordered like
12 13 14 15
  8   9  10 11
  4   5    6   7
  0   1    2   3

I've read the MPI-3 manual at http://www.mpi-forum.org/docs/mpi-3.0/mpi30-report.pdf

What am I missing?  Can I manipulate the rank placement produced by MPI_Cart_create to suite this application?

Daniel Kokron
NASA Ames (ARC-TN)
SciCon group
301-286-3959