Sorry for the delay in replying -- INBOX deluge makes me miss emails
on the users list sometimes.
I'm unfortunately not familiar with gamess -- have you checked with
their support lists or documentation?
Note that Open MPI's IB progression engine will spin hard to make
progress for message passing. Specifically, if you have processes
that are "blocking" in message passing calls, those processes will
actually be spinning trying to make progress (vs. actually blocking in
the kernel). So if you overload your hosts -- meaning that you run
more Open MPI jobs than there are cores -- you could well experience
dramatic slowdown in overall performance because every MPI job will be
competing for CPU cycles.
On Feb 24, 2009, at 4:57 AM, Thomas Exner wrote:
Dear all:
Because I am new to this list, I would like to introduce myself as
Thomas Exner and please excuse silly questions, because I am only a
chemist.
And now my problem, with which I am fiddling around for almost a
week: I
try to use gamess with openmpi on infiniband. There is a good
description on how to compile it with mpi and it can be done, even if
it is not easy. But then on run time everything gets weird. The
specialty of gamess is that it runs twice as much mpi jobs than used
for
the computation. The second half is used as data server, requiring
data
but with very little cpu load. Each one of these data servers is
connected to a specific compute job. Therefore, these two
corresponding
jobs have to be run on the same node. On one node everything is fine
(2x4core machines in my case), because all the jobs are guarantied to
run on this node. If I try two nodes, at the beginning also everything
is fine. 8 compute jobs and 8 data server are running on each machine.
But after a short while, the entire set of processes (16) on the first
node start to accumulate CPU time, with nothing useful happening. The
second node's processes go entirely to sleep. Is it possible that all
the compute jobs are for some reason been transfered to the first
node?
This would explain the load of 16 on the first and 0 on the second
node,
because 16 compute jobs (100 % cpu load) and 16 data servers (almost
0%
load) are running, respectively. Strange thing is also that the same
version runs on gigabit and myrinet fine.
It would be great if somebody could help me on that. If you need more
information, I will be happy to share them with you.
Thanks very much.
Thomas
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Jeff Squyres
Cisco Systems
