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William Gropp ha scritto:
<blockquote cite="mid:3220113C-9113-4570-8219-A86B2A520C0D@mcs.anl.gov"
type="cite">Roberto,
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<div>Pack and Unpack were provided for applications that were used to
the PVM style of building messages - as others have mentioned, MPI
provided datatypes to permit a good MPI implementation to optimize the
handling of non-contiguous data.</div>
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Ok! I see, thanks a lot.<br>
<blockquote cite="mid:3220113C-9113-4570-8219-A86B2A520C0D@mcs.anl.gov"
type="cite">
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<div>Bill</div>
<div><br>
<div>
<div>On Jul 31, 2008, at 12:18 PM, Roberto Fichera wrote:</div>
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<blockquote type="cite">
<div style="margin: 0px;">Hi All on the list,</div>
<div style="margin: 0px; min-height: 14px;"><br>
</div>
<div style="margin: 0px;">My apologies if this argument was already
well discussed many times</div>
<div style="margin: 0px;">before in the list, but playing around the</div>
<div style="margin: 0px;">MPI_Send() and MPI_Recv() I end up on
trying to optimize both transfert</div>
<div style="margin: 0px;">and receive parts for our</div>
<div style="margin: 0px;">serialization/deserialization functions.
So looking around I decide to</div>
<div style="margin: 0px;">use the MPI_Pack() and MPI_Unpack() into</div>
<div style="margin: 0px;">an already allocated buffer and
send/receive it in one "big shot". After</div>
<div style="margin: 0px;">getting it working I finally created a
test program</div>
<div style="margin: 0px;">for profiling the performances in both
cases. My results was quite</div>
<div style="margin: 0px;">stunning, working with various sizes in
Mb of serialized</div>
<div style="margin: 0px;">data, the MPI_Send() is ~2 to 4 times
faster than paired MPI_Pack() &</div>
<div style="margin: 0px;">MPI_Send()!!! So, my understanding for the</div>
<div style="margin: 0px;">MPI_Pack() is that it can be usefull for
packing and unpacking data to</div>
<div style="margin: 0px;">send/receive for performance reasons,
maybe</div>
<div style="margin: 0px;">do I'm missing something (o.s. tuning)?</div>
<div style="margin: 0px; min-height: 14px;"><br>
</div>
<div style="margin: 0px;">I'm using mpich2 v1.0.7 with channel
ch3:socket on Fedora 8 x86_64.</div>
<div style="margin: 0px; min-height: 14px;"><br>
</div>
<div style="margin: 0px;">Best regards,</div>
<div style="margin: 0px;">Roberto Fichera.</div>
<div style="margin: 0px; min-height: 14px;"><br>
<span><char.png></span><span><double.png></span><span><int.png></span></div>
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<div>William Gropp</div>
<div>Paul and Cynthia Saylor Professor of Computer Science</div>
<div>University of Illinois Urbana-Champaign</div>
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