Beware that MPI-request-free on active buffers is valid but evil. You CANNOT be sure when the buffer is available for reuse.
There was a sentence or paragraph added yo MPI 2.2 describing exactly this case.
Sent from my PDA. No type good.
On Nov 23, 2010, at 5:36 PM, SÃ©bastien Boisvert <Sebastien.Boisvert.3_at_[hidden]> wrote:
> Le mardi 23 novembre 2010 Ã 17:28 -0500, George Bosilca a Ã©crit :
>> Using MPI_Isend doesn't guarantee asynchronous progress. As you might be aware, the non-blocking communications are guaranteed to progress only when the application is in the MPI library. Currently very few MPI implementations progress asynchronously (and unfortunately Open MPI is not one of them).
> Regardless, I just need the non-blocking behavior.
> I call MPI_Request_free just after MPI_Isend, and I use a ring allocator
> to allocate message buffers.
> Message recipients just reply with another message to the source, using
> a NULL buffer.
> The sender waits for the reply before sending the next message.
> And it works for assembling bacterial genomes on many MPI ranks:
> Rank 0: 162 contigs/4576725 nucleotides
> Rank 0 reports the elapsed time, Tue Nov 23 01:35:48 2010
> ---> Step: Collection of fusions
> Elapsed time: 0 seconds
> Since beginning: 17 minutes, 33 seconds
> Elapsed time for each step, Tue Nov 23 01:35:48 2010
> Beginning of computation: 1 seconds
> Distribution of sequence reads: 7 minutes, 49 seconds
> Distribution of vertices: 19 seconds
> Calculation of coverage distribution: 1 seconds
> Distribution of edges: 29 seconds
> Indexing of sequence reads: 1 seconds
> Computation of seeds: 2 minutes, 33 seconds
> Computation of library sizes: 1 minutes, 47 seconds
> Extension of seeds: 3 minutes, 34 seconds
> Computation of fusions: 59 seconds
> Collection of fusions: 0 seconds
> Completion of the assembly: 17 minutes, 33 seconds
> Rank 0 wrote Ecoli-THEONE.CoverageDistribution.txt
> Rank 0 wrote Ecoli-THEONE.fasta
> Rank 0 wrote Ecoli-THEONE.ReceivedMessages.txt
> Rank 0 wrote Ecoli-THEONE.Library0.txt
> Rank 0 wrote Ecoli-THEONE.Library1.txt
> Au revoir !
>> On Nov 23, 2010, at 17:17 , SÃ©bastien Boisvert wrote:
>>> I now use MPI_Isend, so the problem is no more.
>> devel mailing list
> M. SÃ©bastien Boisvert
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