[mvapich-discuss] MVAPICH2 Derived datatypes performance issue (vs. MVAPICH)

[Sayantan Sur]

Hello Eric,

Thanks for sharing this information! Actually, this performance problem
has been recently fixed in the MPICH2-1.0.5 stack. MVAPICH2-0.9.8 is
based on the MPICH2-1.0.3 stack. We are currently working on upgrading
MVAPICH2 to the latest MPICH2-1.0.5 stack. This update will be a part of
the next MVAPICH2-0.9.9 release.

Thanks,
Sayantan.

* On Dec,1 Eric A. Borisch<eborisch at ieee.org> wrote :
> Good afternoon all,
> 
> I have been trying to understand some performance disparities between
> two MPI installations that go well beyond the expected multirail
> differences. The problem seems to come from derived datatype
> performance. My two test conditions are:
> 
> (A) MVAPICH (VAPI_multirail) and
> (B) MVAPICH2 (VAPI)
> 
> To make sure I wasn't just doing something odd in my code, and
> hopefully make it easy for others to test as well, I've used the
> "transp-datatype.c" test that can be found in an mpich2-1.0.5
> distribution in "mpich2-1.0.5/test/mpi/perf/transp-datatype.c"
> 
> I bumped the SIZE up to 1024 on a side for the arrays to be transposed
> & communicated -- other than that I've taken the code as is...
> 
> Running under MVAPICH, the communication & transpose via derived
> datatypes takes ~55msec, while on MVAPICH2, it takes ~1300msec. This
> is not a typo -- it takes 24x longer on MVAPICH2. If you try running
> the code, this is the first value that is returned (in seconds) on
> execution.
> 
> The straight-through (no transpose or derived datatypes) test shows
> reasonable timings of 5.8ms and 8.9ms -- ~1350 MB/s and ~900 MB/s --
> respectively.
> 
> These tests are performed on the same two machines in each case. Each
> is a dual 3.4G P4, with a PCI-E dual-port SDR card and 4GB of ram;
> running ROCKS 4.1.
> 
> Any thoughts or suggestions?
> 
> Thanks in advance,
> Eric Borisch
> Radiology Research
> Mayo Clinic
> 
> -- 
> Eric A. Borisch
> eborisch at ieee.org
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