I am invoking MPI_Init_thread() with MPI_THREAD_MULTIPLE. If openib BTL is responsible for the warning and openib BTL is excluded in this case, then that explains the discrepancy.

FYI, I invoked MPI_Init_thread() with MPI_THREAD_SERIALIZED and I got the warning message about the fork().



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Subject: Re: [OMPI devel] Warning on fork() disappears if I use MPI threads!!
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-11-29 14:10:44

On Nov 23, 2010, at 3:23 PM, <ananda.mudar_at_[hidden]> <ananda.mudar_at_[hidden]> wrote:

> However this error message goes away, if I initialize MPI with threads ie; MPI_Init_thread(). Can anyone explain this discrepancy?

What thread level are you invoking MPI_INIT_THREAD with?

One possible reason this could be happening is that the openib BTL is excluding itself if you use MPI_THREAD_MULTIPLE. The openib BTL is the entity that is responsible for the fork warning -- if it's not being used, then no warning is issued because there is no problem with forking.

Jeff Squyres
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