[gpaw-users] Computational cost of vdW-DF

[andreasm at fysik.dtu.dk]

I guess you can change the number of kernels to be consistent with the
number of cpus
For example using 16 cpus:
vdw=FFTVDWFunctional(name='vdW-DF2',Nalpha=16)
Than everything above 16 cpus will only help the GGA part of the
calculations.

I have a question in this respect. What would take to change the
implementation such that you could use more cpus? It would be very helpful
if one could use 32 or even 64...

Best
Andreas

> 2011/4/12 Jens Jørgen Mortensen <jensj at fysik.dtu.dk>:
>> On Tue, 2011-04-12 at 15:29 +0200, Duy Le wrote:
>>> 2011/4/12 Jens Jørgen Mortensen <jensj at fysik.dtu.dk>:
>>> > On Mon, 2011-04-11 at 23:56 +0200, Duy Le wrote:
>>> >> Dear all,
>>> >> As I understand, the approach of Román-Pérez and Soler (PRL 2009)
>>> has
>>> >> been implemented in GPAW.  I wonder why the self-consistent vdW-DF
>>> >> calculation is still extremely expensive (3 or 4 times in most of my
>>> >> calculations) in comparison to regular GGA-PBE calculation.
>>> >> Does any of you experience this slowness? I would like to know the
>>> reason.
>>> >
>>> > For a small system with few electrons, the calculation of the vdW-DF
>>> > potential will dominate.  With more electrons the vdW-DF part should
>>> > become smaller unless you run on so many cores that the
>>> parallelization
>>> > of the vdW-DF stuff stops scaling.  So, what is your system and how
>>> many
>>> > cpu's do you use?
>>> It is the case, my systems are big, in the order of about 70-150
>>> atoms. Of course I have to use lot of cores (64 to 512 cores in most
>>> of the case) otherwise I don't have enough memory allocated.
>>> Is there any way to improve it? The PBE calculation is scaled very
>>> well.
>>
>> The current implementation of the vdW-DF xc-potential scales only up to
>> 20 cores.  Could you show us the text output from one of your
>> calculations - you should be able to see the timings for the different
>> parts of the calculation in the text output.
>>
> Sure. Check attachments for a scf PBE and vdW-DF1. I deleted many
> lines which are not so important.
> Those are done with 64 cores on AIX power6.
> --------------------------------------------------
> Duy Le
> PhD Student
> Department of Physics
> University of Central Florida.
>
> "Men don't need hand to do things"
>> Jens Jørgen
>>
>>> > Jens Jørgen
>>> >
>>>
>>> --------------------------------------------------
>>> Duy Le
>>> PhD Student
>>> Department of Physics
>>> University of Central Florida.
>>>
>>> "Men don't need hand to do things"
>>> >> Thank you.
>>> >> --------------------------------------------------
>>> >> Duy Le
>>> >> PhD Student
>>> >> Department of Physics
>>> >> University of Central Florida.
>>> >>
>>> >> "Men don't need hand to do things"
>>> >>
>>> >> _______________________________________________
>>> >> gpaw-users mailing list
>>> >> gpaw-users at listserv.fysik.dtu.dk
>>> >> https://listserv.fysik.dtu.dk/mailman/listinfo/gpaw-users
>>> >
>>> >
>>
>>
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