At 10:31 PM 11/27/2007, you wrote:
Hello,
Because today the clusters with multicore nodes are quite common
and the cores within a node share memory.
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).
regards,
Ali.
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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:
www.pvmmpi06.org/talks/CommProt/buntinas.pdf
<http://info.mcs.anl.gov/pub/tech_reports/reports/P1346.pdf>info.mcs.anl.gov/pub/tech_reports/reports/P1346.pdf
ftp.mcs.anl.gov/pub/mpi/mpich2-doc-CHANGES.txt.
We are getting higher latencies than that on various hardware, so
obviously YMMV.
Mike
Oops, sorry. Early morning typing-while-sleeping.
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.
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.
Mike
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