From: Andre' Burke <aburke@intch.co.za>
Newsgroups: comp.parallel.mpi
Subject: Limited process numbers on Linux
Date: Mon, 31 Aug 1998 14:23:45 +0200
Organization: An Internet Solution Customer
Message-Id: <35EA95D1.EBA625E8@intch.co.za>
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Hi all,

I have just installed MPI on my Linux box and after some initial
problems have got it to pass all the standard tests that came with the
package.

However this only works for a small number of processes, eg. 3 or less.
I have two machines connected in a network, but plan to add more as
budget allows.

Whenever I try to use 4 or more processes the job never finishes.
It appears to start the processes but if two many processes are running
on the slave machine, then only one of the processes appears to actually
do anything (and it never finishes anyway) but the other processes seem
to do nothing.

I have come across the following possible reasons for the problem.

1. RSH limits the amount of processes you can create.
2. RSH limits the amount of processes allowed to write to stdout.

Neither really seems the correct choice, as when only running on one
machine I can create as many as I like and it runs (does it use RSH on
the localhost?).
But as soon as I use the slave machine with a number of processes it
refuses to finish.

If its stdout, I assume I could get around it by writing to a file
instead of to stdout.

The guide suggested using the secure server to get around this problem,
but I tried this with no measurable difference.

Any suggestions would be greatly appreciated.

MPI Newbie,
Andre' Burke

andreb@gmsi.co.za