Le mardi 23 novembre 2010 à 16:07 -0500, Eugene Loh a écrit :
Sébastien Boisvert wrote:
Case 1: 30 MPI ranks, message size is 4096 bytes
File: mpirun-np-30-Program-4096.txt
Outcome: It hangs -- I killed the poor thing after 30 seconds or so.
4096 is rendezvous. For eager, try 4000 or lower.
According to ompi_info, the threshold is 4096, not 4000, right ?
Right.
"btl_sm_eager_limit: Below this size, messages are sent "eagerly" --
that is, a sender attempts to write its entire message to shared buffers
without waiting for a receiver to be ready. Above this size, a sender
will only write the first part of a message, then wait for the receiver
to acknowledge its ready before continuing. Eager sends can improve
performance by decoupling senders from receivers."
source:
http://www.open-mpi.org/faq/?category=sm#more-sm
It should say "Below this size or equal to this size" instead of "Below
this size" as ompi_info says. ;)
Well, I guess it should say:
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