[mpich-discuss] Relative ordering of MPI_Iprobe()s and MPI_Barrier()s

[michael bane]

I'd concur with others that it's the *MPI_Send* (not timing of barriers)
that are presumptious and should be changed for portability (to buffered
sends since that's your presumption). You may find that solves your
deadlock. There's no guarantee MPI_Send will buffer. Period.

I've been caught out in the past (with solutions to a course!) by
presuming how MPI_Send works - indeed, I found depending if intra- or
inter- node and on the choice of lower level implementation details that
it could well hang, demonstrably.

Yours, Michael Bane
http://www.twitter.com/mkbane_mcr

On Wed, 2010-08-18 at 09:38 +0100, Edric Ellis wrote:
> Hi Darius,
> 
> Thanks for that - I haven't tried 1.3b1 yet - but that patch applied on its own to 1.2.1p1 appears to cause my example program to lock up because some of the Iprobes appear never to succeed.
> 
> Based on what Dave and Anh have said, it sounds like the right approach is for us not to make assumptions about the relative timing of barriers and probes. (Which leaves us with a puzzle of how to test our wrapper around MPI_Barrier...)
> 
> Cheers,
> 
> Edric.
> 
> > -----Original Message-----
> > From: mpich-discuss-bounces at mcs.anl.gov [mailto:mpich-discuss-
> > bounces at mcs.anl.gov] On Behalf Of Darius Buntinas
> > Sent: Tuesday, August 17, 2010 7:42 PM
> > To: mpich-discuss at mcs.anl.gov
> > Subject: Re: [mpich-discuss] Relative ordering of MPI_Iprobe()s and
> > MPI_Barrier()s
> > 
> > 
> > Can you try this patch (it's based on the trunk, but it should be simple
> > enough that it should still apply)?
> > 
> > http://mpich2.pastebin.com/z7ASbdrk
> > 
> > -d
> > 
> > On Aug 17, 2010, at 11:15 AM, Dave Goodell wrote:
> > 
> > > On Aug 17, 2010, at 11:14 AM CDT, Darius Buntinas wrote:
> > >
> > >> I believe we might have fixed this.  Can you send us the test program, or
> > try 1.3b1?
> > >
> > > I believe it was attached to the original email...
> > >
> > > -Dave
> > >
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