Rajeev Thakur thakur at
Wed Jun 18 15:19:57 EDT 2003

> Date: Wed, 18 Jun 2003 16:02:22 -0300
> From: Renato Silva <rssr at>
> Cc: beowulf at
> Hi Folks
> Does anybody knows what are the communication algorithm used in the
> mpich-2.5
> to do the Reduce-to-all ?
> Thanks
> Renato Silva

All the collective algorithms are described in the source code. See the file
src/coll/intra_fns_new.c and look for MPI_Allreduce. The next release of
MPICH will have a different algorithm for long-message allreduce.


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