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Subject: Re: [OMPI users] Configuration for rendezvous and eager protocols: two-sided comm
From: Siddhartha Jana (siddharthajana24_at_[hidden])
Date: 2013-12-16 03:49:01


Thanks Christoph.
I should have looked into the FAQ section on MCA params setting @ :
http://www.open-mpi.org/faq/?category=tuning#available-mca-params

Thanks again,
-- Siddhartha

On 16 December 2013 02:41, Christoph Niethammer <niethammer_at_[hidden]> wrote:

> Hi Siddhartha,
>
> MPI_Send/Recv in Open MPI implements both protocols and chooses based on
> the message size which one to use.
> You can use the mca parameter "btl_sm_eager_limit" to modify the behaviour.
>
> Here the corresponding info obtained from the ompi_info tool:
>
> "btl_sm_eager_limit" (current value: <4096>, data source: default value)
> Maximum size (in bytes) of "short" messages (must be >= 1)
>
> Regards
> Christoph Niethammer
>
> --
>
> Christoph Niethammer
> High Performance Computing Center Stuttgart (HLRS)
> Nobelstrasse 19
> 70569 Stuttgart
>
> Tel: ++49(0)711-685-87203
> email: niethammer_at_[hidden]
> http://www.hlrs.de/people/niethammer
>
>
>
> ----- Ursprüngliche Mail -----
> Von: "Siddhartha Jana" <siddharthajana24_at_[hidden]>
> An: "OpenMPI users mailing list" <users_at_[hidden]>
> Gesendet: Samstag, 14. Dezember 2013 13:44:12
> Betreff: [OMPI users] Configuration for rendezvous and eager protocols:
> two-sided comm
>
>
>
> Hi
>
>
> In OpenMPI, are MPI_Send, MPI_Recv (and friends) implemented using
> rendezvous protocol or eager protocol?
>
>
> If both, is there a way to choose one or the other during runtime or while
> building the library?
>
>
> If there is a threshold of the message size that dictates the protocol to
> be used, is there a way I can alter that threshold value?
>
>
> If different protocols were used for different versions of the library in
> the past, could someone please direct me to the exact version numbers of
> the implementations that used one or the other protocol?
>
>
> Thanks a lot,
> Siddhartha
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