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From: Pak Lui (Pak.Lui_at_[hidden])
Date: 2006-05-31 14:11:25


When I run a spawn program over rsh/ssh, I notice that each time the
child program gets spawned, it will need to establish a new rsh/ssh
connection to the remote node to launch orted on that node, even the
parent executable and the orted are running on that node.

So I wonder if there is any way that we can use the parent orted to
launch the child program if they happen to be on the same node?

I try to compare to the spawn program to the scenario where I run
multiple executables in one mpirun command. For this run, I only
establish one connection to the remote node only, and both executables
shared the same remote connection.

% ./mpirun -np 2 -host burl-ct-v440-5 -prefix `pwd`/.. sleep 12 : -np 2
sleep 10

15015 /workspace/paklui/ompi/trunk/builds/sparc32-g/bin/../bin/orted
   15017 sleep 12
   15019 sleep 12
   15021 sleep 10
   15023 sleep 10

The reason that I want to find out if it is possible for orted to launch
child executable(s) without having to establish a new connection, is
because the number of times that I can run 'qrsh' in SGE (or N1GE) is
actually depended on the number of slots that the user initially
allocated. That the slot number corresponds to the number of CPUs on a
node. Each slot allows one 'qrsh' connection.

The issue is when I try to run a spawn job on a single node, or a
cluster of many 1-cpu nodes under SGE. The number of times that the
program can spawn is limited by 'qrsh', that it forbids the child
program to connect to the same node where the parent executable's orted
might be already running there.

I am curious to see if I can find some solution to the problem here. I
am also looking to see if there are some tricks in SGE to get around
this issue, but workaround I can see aren't pretty though. So I welcome
your questions, comments or suggestions on this.

- Pak Lui