[mpich-discuss] MPI_Allgatherv complexity

Pavan Balaji balaji at mcs.anl.gov
Mon Nov 2 18:37:33 CST 2009

On 11/02/2009 06:27 PM, Justin Luitjens wrote:
> Actually I just realized I was wrong with what I said.  Our code has a
> lot of variation but the allgather test that I wrote and timed in the
> graph I attached will only have a single element of variation between
> each process.  Is there an environment variable I can set to force
> either the ring algorithm or the recursive doubling algorithm to compare
> the times? 

No, there's no such provisioning (though we should probably add it).

This does look like a performance issue. Can you create a ticket here:


 -- Pavan

Pavan Balaji

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