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<blockquote type=cite class=cite cite="">At 10:31 PM 11/27/2007, you
wrote:<br>
<blockquote type=cite class=cite cite="">Hello,<br>
<br>
Because today the clusters with multicore nodes are quite common and the
cores within a node share memory. <br>
<br>
Which Implementations of MPI (no matter commercial or free), make
automatic and efficient use of shared memory for message passing within a
node. (means which MPI librarries auomatically communicate over shared
memory instead of interconnect on the same node). <br>
<br>
regards,<br>
Ali.<br>
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The latest MPICH2 from Argonne (may be version 1.06) complied for the
ch3:nemesis shared memory device has very low latency -- as low as 0.06
microseconds -- and very high bandwidth. It beats LAM in Argonne's
tests. Here are details: <br><br>
<a href="http://www.pvmmpi06.org/talks/CommProt/buntinas.pdf" eudora="autourl">
www.pvmmpi06.org/talks/CommProt/buntinas.pdf</a><br>
<a href="http://info.mcs.anl.gov/pub/tech_reports/reports/P1346.pdf">
info.mcs.anl.gov/pub/tech_reports/reports/P1346.pdf</a><br>
<a href="ftp://ftp.mcs.anl.gov/pub/mpi/mpich2-doc-CHANGES.txt" eudora="autourl">
ftp.mcs.anl.gov/pub/mpi/mpich2-doc-CHANGES.txt</a>.<br><br>
We are getting higher latencies than that on various hardware, so
obviously YMMV.<br><br>
<br>
Mike </blockquote><br>
Oops, sorry. Early morning typing-while-sleeping.<br><br>
The latencies claimed by Argonne for core-to-core on-board
communication with MPICH2 compiled using the ch3:nemesis device are
0.3-0.5 microseconds, not 0.06. There's also no claim about what
happens when you use it for mixed on-board and off-board comms.<br><br>
Our recent dual-core 64-bit AMD boards get 0.6 microsecond latency
core-to-core, while our older 32-bit ones get 1.6. That's all by
netpipe test.<br><br>
<br>
Mike</body>
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