[Fwd: Re: [gmx-users] mdrun CVS version crashes instantly when run across nodes in parallel]

[Berk Hess]

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> Date: Tue, 22 Jan 2008 20:15:03 +0100
> From: ckutzne at gwdg.de
> To: gmx-users at gromacs.org
> Subject: [Fwd: Re: [gmx-users] mdrun CVS version crashes instantly when run	across nodes in parallel]
> 
> Hi Erik,
> 
> I have made a test with today's CVS version and I also run into the
> problem you described. It happens as soon as one uses more than one node
> and at the same time more than one process per node.
> 
> The problem seems to be in gmx_sumd where in the two-step summation in a
> call to MPI_Allreduce the variable cr->nc.comm_inter happens to be a
> NULL pointer, which should clearly not be.
> 
> The inter-node communicator is freed in gmx_setup_nodecomm (network.c,
> line 393) if an intra-node communicator is present - I do not understand
>  why the communicator is freed here.
> 
> Maybe Berk can help us on that? If I comment out the MPI_Comm_free the
> code runs happily - haven't checked the results, though.
> 
> Carsten

Ah, there is a "typo" in the conditional, it should be rank_intra iso comm_intra.
I have committed the fix.

Thanks,

Berk.

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