[CP2K:6419] PLUMED 2 only running on 1 core

[Iain Bethune]

Hi Omar, the ‘bug’ is actually the PLUMED patch working as currently intended.  PLUMED is only ever initialised on a single process.  This was done for simplicity, and for most CP2K calculations, the amount of time spent evaluating forces using QS will massively outweigh the amount of work PLUMED has to do, hence a parallel implementation will not make a noticeable difference.  In a classical code like Gromacs where the force evaluation is (relatively) cheap, the cost of the CV calculation matters more.

That said, it should be possible to make the PLUMED/CP2K integration fully parallel, and I will look into this.  The current implementation is correct i.e. you will get the same results independent of the number of processes you are running on.

- Iain

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Iain Bethune
Project Manager, EPCC

Email: ibet... at epcc.ed.ac.uk
Twitter: @IainBethune
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> On 28 Apr 2015, at 09:43, Iain Bethune <ibet... at epcc.ed.ac.uk> wrote:
> 
> Hi Omar,
> 
> Thanks for pointing this out - I have tried locally and it is indeed a bug.  I’ll get back to you when I have a fix.
> 
> Cheers
> 
> - Iain
> 
> --
> 
> Iain Bethune
> Project Manager, EPCC
> 
> Email: ibet... at epcc.ed.ac.uk
> Twitter: @IainBethune
> Web: http://www2.epcc.ed.ac.uk/~ibethune
> Tel/Fax: +44 (0)131 650 5201/6555
> Mob: +44 (0)7598317015
> Addr: 2404 JCMB, The King's Buildings, Peter Guthrie Tait Road, Edinburgh, EH9 3FD
> 
>> On 28 Apr 2015, at 08:10, Valsson <omar.v... at gmail.com> wrote:
>> 
>> Hello, 
>> 
>> I am trying to use CP2K with PLUMED 2 using the built-in interface but I am having the problem that PLUMED 2 seems to run only in serial. 
>> 
>> I launch CP2K (popt binary) on 24 cores but in the PLUMED.OUT file I obtain 
>> 
>> PLUMED: Running over 1 node
>> PLUMED: Number of threads: 1
>> 
>> so it seems that PLUMED 2 is running on only 1 core while cp2k is using 24 cores. 
>> 
>> So my question is, does the plumed 2 interface in cp2k only run plumed 2 in serial? Or I am doing something wrong in the compilation of cp2k? 
>> 
>> Note that I am using the same plumed 2 compilation with Gromacs and there plumed runs in parallel without any problems. 
>> 
>> Regards,
>> Omar
>> 
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