[gmx-users] GROMACS Parallel Runs

Dallas B. Warren Dallas.Warren at vcp.monash.edu.au
Fri Oct 6 01:35:31 CEST 2006

> 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)

Isn't that just due to the reasoning pointed out previously ....

>>the current version of gmx requires at least pme_order/2 grid points 
>>for the x-dimension of the pme grid. With pme_order=4 and
>>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
>>are not
>>useful for 32 or less CPUs though, because they would unnecessarily
>>down your

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