Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |  

This web mail archive is frozen.

This page is part of a frozen web archive of this mailing list.

You can still navigate around this archive, but know that no new mails have been added to it since July of 2016.

Click here to be taken to the new web archives of this list; it includes all the mails that are in this frozen archive plus all new mails that have been sent to the list since it was migrated to the new archives.

Subject: Re: [OMPI users] OpenMPI runtime-specific environment variable?
From: Jed Brown (jed_at_[hidden])
Date: 2008-10-22 04:30:46

On Wed 2008-10-22 00:40, Reuti wrote:
> Okay, now I see. Why not just call MPI_Comm_size(MPI_COMM_WORLD,
> &nprocs) When nprocs is 1, it's a serial run. It can also be executed
> when not running within mpirun AFAICS.

This is absolutely NOT okay. You cannot call any MPI functions before
MPI_Init (and at least OMPI 1.2+ and MPICH2 1.1a will throw an error if
you try).

I'm slightly confused about the original problem. Is the program linked
against an MPI when running in serial? You have to recompile anyway if
you change MPI implementation, so if it's not linked against a real MPI
then you know at compile time. But what is the problem with calling
MPI_Init for a serial job? All implementations I've used allow you to
call MPI_Init when the program is run as ./foo (no mpirun).


  • application/pgp-signature attachment: stored