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Subject: Re: [OMPI users] Segfault in with > ~100 process.
From: Oliver Ford (openmpi_at_[hidden])
Date: 2010-02-27 09:02:38

Ralph Castain wrote:
> Yeah, the system won't like this. Your approach makes it look like you are launching 136 app_contexts. We currently only support up to 128 app_contexts. I don't think anyone anticipated somebody trying to use the system this way.
> I can expand the number to something larger. Will have to see how big a change it requires (mostly a question of how many places are touched) before we know what release this might show up in.
The app_context allocation is all dynamic so is fine, the problem that
'app_idx' (various structures and code) which appears to be some kind of
index mapping is defined as int8_t, so everything goes negative after
128 - hence the segfault.

Attached is a patch to the openmpi-1.4.1 taball on the website to make
it all int32_t, which I've tested and works fine.

I've also attached a patch for the current SVN head, which compiles but
I can't test it because the current SVN head doesn't work for me at all
at present (for an appfile with less than 128 entries).

Sorry to send this here rather than the dev list, but I don't really
have the time to sign up and get involved at the moment.

Hope that helps a bit,