[gmx-users] GROMACS Parallel Runs

Sunny ge_sunny at hotmail.com
Thu Oct 5 16:54:47 CEST 2006

Hi all,

I have successfully run gmx on up to 128 cpus. When I scale to 256 cpus, the 
following error occurs. Does it mean that gmx can't be run on 256 nodes?

Fatal error:
could not find a grid spacing with nx and ny divisible by the number of 
nodes (256)



>From: "Sunny" <ge_sunny at hotmail.com>
>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>To: gmx-users at gromacs.org
>Subject: Re: [gmx-users] GROMACS Parallel Runs
>Date: Tue, 03 Oct 2006 09:57:43 +0000
>Hi Carsten,
>Setting fourier_nx to a larger number does work.
>>From: Carsten Kutzner <ckutzne at gwdg.de>
>>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>>To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>>Subject: Re: [gmx-users] GROMACS Parallel Runs
>>Date: Mon, 02 Oct 2006 11:06:49 +0200
>>the current version of gmx requires at least pme_order/2 grid points per 
>>for the x-dimension of the pme grid. With pme_order=4 and fourier_nx=64 
>>you end up with
>>only one grid point per processor. On 64 CPUs you would have to set 
>>fourier_nx to 128
>>then (or alternatively choose a smaller fourierspacing). These settings 
>>are not
>>useful for 32 or less CPUs though, because they would unnecessarily slow 
>>down your
>>Hope that helps,
>>   Carsten

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