https://wiki.alcf.anl.gov/parts/index.php/Implementing_a_Symmetric_Heap has an implementation of MPE_Comm_split_node that does a very simple O(Nproc) implementation of MPI_Comm_split_type(type=SHARED) using MPI_Get_processor_name.  It also shows the non-portable implementation for Cray and Blue Gene that one can use until MPI-3 is deployed on those systems.

Jim Dinan wrote an O(log Nproc) implementation of MPI_Comm_split_type(type=SHARED) that I have somewhere but I don't like it because it's confusing to my small brain.

Jeff

----- Original Message -----
From: "Rob Latham" <robl@mcs.anl.gov>
To: devel@mpich.org
Sent: Wednesday, July 3, 2013 10:53:15 AM
Subject: Re: [mpich-devel] find out what processes are on the same node

On Wed, Jul 03, 2013 at 10:39:55AM -0500, Tatiana V. Martsinkevich wrote:

Hello,

I have a couple of questions:

1) is there a way to find out what other processes reside in the same

node as my_rank from within MPICH?

MPI_GET_PROCESSOR_NAME might be what you are looking for.  

==rob

--
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA

--
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond@alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
ALCF docs: http://www.alcf.anl.gov/user-guides