[mpich-discuss] Strange behavior of mpd
Bellanca Gaetano
gaetano.bellanca at unife.it
Tue Sep 30 11:19:09 CDT 2008
Hi Gus and list,
I thought (hope!) that increasing the dimension of the MPI buffer
size can produce the same effect ... without writing other code. I
agree with you that having to manage smaller messages should be
simpler. However, I was surprised to have the same behavior on two
very different PCs (the one at home, with a single CPU and 4GB of
RAM, and the one at the University, with 2 processors and 16GB of RAM).
Moreover, I changed the code (before I had MPI_SEND and MPI_RECV, now
I have MPI_GATHERV implemented), and I had the same error in the same
point of the code. This seems to confirm that the dimension of the
message is the problem.
However, when I discovered that simply killing and restarting mpd, or
having mpd started by hands after the boot, is a solution to this
problem, I thought that I can use this as a possible way to overcome it.
Rajeev (thanks Rajeev for your comment!) pointed out that mpd doesn't
interfere with MPI communication; so I can't explain really what's
happening. But I observed this behavior.
About the dimension of the message, the computational domain is
326x118x328 wide, and when partitioned by two becomes 163x118x326 ->
627284 real values. I have no idea if this could be a too big message.
Maybe I did the same mistake compiling and installing mpich, so that
it doesn't work correctly (from this point of view; results are
correct and the same running on 1PE and on #PEs)?
Regards.
G
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Gaetano Bellanca - Department of Engineering - University of Ferrara
Via Saragat, 1 - 44100 - Ferrara - ITALY
Voice (VoIP): +39 0532 974809 Fax: +39 0532 974870
mailto:gaetano.bellanca at unife.it
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