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Subject: Re: [OMPI users] Is Iprobe fast when there is no message to recieve
From: Ashley Pittman (ashley_at_[hidden])
Date: 2009-10-03 16:15:24


On Sat, 2009-10-03 at 07:05 -0400, Jeff Squyres wrote:
> That being said, if you just want to send a quick "notify" that an
> event has occurred, you might want to use a specific tag and/or
> communicator for these extraordinary messages. Then, when the event
> occurs, send a very short message on this special tag/communicator
> (potentially even a 0-byte message).

> You can MPI_TEST for
> the completion of this short/0-byte receive very quickly. You can
> then send the actual data of the event in a different non-blocking
> receive that is only checked if the short "alert" message is received.

In general I would say that Iprobe is a bad thing to use, as Jeff says
post a receive in advance and then call test on this receive rather than
using Iprobe.

>From your description it sounds like a zero byte send is all you need
which should be fast in all cases.

Ashley,

-- 
Ashley Pittman, Bath, UK.
Padb - A parallel job inspection tool for cluster computing
http://padb.pittman.org.uk