[gpaw-users] Changes in the new PAW setups bundle of 26/10 ("gpaw-setups-0.9.9672")

[Marcin Dulak]

On 11/23/12 16:01, Ask Hjorth Larsen wrote:
> Hi
>
> 2012/11/23 Marcin Dulak <Marcin.Dulak at fysik.dtu.dk>:
>> Hi,
>>
>>
>> On 11/23/12 15:03, Ask Hjorth Larsen wrote:
>>> Hi
>>>
>>> 2012/11/23 Marcin Dulak <Marcin.Dulak at fysik.dtu.dk>:
>>> (...)
>>>> A negative outcome from the way new setups are generated is that most of
>>>> them require now eigensolver='cg' or 'dav' to achieve convergence.
>>>> The new Oxygen setup is also a bit harder, so requires finer grid.
>>>>
>>>> Best regards,
>>>>
>>>> Marcin
>>> This last part is rather unfortunate because cg and dav, compared to
>>> rmm-diis, reduce the performance of GPAW by a large factor for systems
>>> of non-trivial size.  Furthermore those solvers don't support band
>>> parallelization AFAIK.  What can be done about this?
>> i remember Jens Jørgen and your comments about that (old Ti setup case),
>> can you remind what was your conclusion?
>> The convergence problems seem to be related to the presence of semicore
>> p-states:
>> https://listserv.fysik.dtu.dk/pipermail/gpaw-developers/2012-September/003190.html
> I don't think anything was concluded other than that it was nasty.
>
> I'm not sure that I have ever seen something that could not be fixed
> with rmm-diis by having a better initialization or adding more states.
>
> Presumably you have some calculations from which it is clear that
> neither of these helps.  But it'll be a major blow if cg is needed as
> a default.  I think it's well below half the performance of rmm-diis
> even when band parallelization is not needed.  So something should be
> figured out. (Small molecules would of course be the exception because
> time is spent on XC/Poisson.)
in fact the link above shows
that starting with cg and switching to rmm (like vasp does) does not 
help for those setups
(see Mixer() initial cg iter:10 on
https://wiki.fysik.dtu.dk/gpaw/documentation/convergence/scf_conv_eval.html#deltacodesdft),
but this has been done with "standard" rmm. I know Jussi is working
on https://wiki.fysik.dtu.dk/gpaw/devel/projects/rmmdiis.html
I have also tried to change the energies of the p-projectors (gpaw-setup 
--extra-projectors),
they have some effect, but still no convergence possible with rmm.
It seems also that no mixers can help, after testing multitude of 
different ones (including Jussi's FFTMixers).

Marcin

>
> Regards
> Ask
>
>


-- 
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Marcin Dulak
Technical University of Denmark
Department of Physics
Building 307, Room 229
DK-2800 Kongens Lyngby
Denmark
Tel.: (+45) 4525 3157
Fax.: (+45) 4593 2399
email: Marcin.Dulak at fysik.dtu.dk

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