[gpaw-users] difference in convergence behavior between versions

[Tristan Maxson]

Hello,  a major difference between gpaw-0.9 and gpaw-0.10 is the default
eigensolver changed.

Try running your calculations with the new gpaw version but ensure the
following settings are set.

Mixer : Use a non-default mixer for both,  or ensure the new gpaw is using
Mixer(0.1,3,50) (The gpaw-0.9 default)

Eigensolver : Ensure both are using the same mixer,  the 0.9 default was
RMM-DIIS and the 0.10 default is davidson.  If you are using RMM-DIIS for
both, import the RMM-DIIS solver from "gpaw.eigensolvers.rmm_diis_old" in
the 0.10 version as the eigensolver was improved in 0.10 but the old one is
still available.

Try setting these and see what your results are.

source:
https://wiki.fysik.dtu.dk/gpaw/devel/releasenotes.html#version-0-10-0

On Wed, Jul 16, 2014 at 9:50 AM, Alfredo Palace Carvalho <ajpalace at uevora.pt
> wrote:

> Hi,
>
> An issue unrelated to my previous email, I don't really know if it is just
> the way it is/should be or if there's really something fishy in here:
> I have recently updated gpaw to the newest stable (0.10.0.11364),
> previously I had been using version gpaw-0.9.1.11146.
> A single point calculation which took, with the older version, 26 SCF
> cycles to converge, now takes 50 iterations with the new version.
> The final results are close but not equal: -235.026624 vs. -235.026593
> At first I thought it could be due to different setups files, but using
> the new version with the new setups and the old ones I just get the same
> results.
> While the two versions of gpaw have been using also different versions of
> ASE, I think I have also excluded the influence of such, because running
> the old gpaw with the new ASE gives the same results (less iterations) than
> if using the old ASE.
> So, the difference has to be due to changes in gpaw.
> I would have accepted it as normal if there was only some slight
> difference. But, now, it takes the double of the previous number of
> iterations. I thought it was too much! What do you think? Is it not
> surprising?
>
> Cheers,
> Alfredo
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