Re: [OMPI devel] Simple program (103 lines) makes Open-1.4.3 hang

[Eugene Loh]

Sébastien Boisvert wrote: 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: If message data plus header information fits within this limit, the message is sent "eagerly"... I guess I'll fix it.  (I suspect I wrote it in the first place.  Sigh.)