[Pw_forum] Nscf with large number of bands for GW

[Kanak Datta]

Dear Thierry

I faced the same Cholesky  problem in my calculation. Although, I
calculated 2000 bands. The problem was gone when we used 'cg'
diagonalization. I also reduced the convergence threshold to 1d-8.
Although, the simulation became very slow, possibly due to 'cg'
diagonalization.

Thanks
Kanak

_______________________________________
Kanak Datta
Graduate Student
Electrical  Engineering and Computer Science
University of Michigan, Ann Arbor

On Wed, Apr 5, 2017 at 11:22 AM, Thierry Clette <thierry.clette at uclouvain.be
> wrote:

> Hello,
>
> I want to do some nscf calculations in order to compute GW corrections
> afterwards. I know that I need a lot of bands to converge, around 3000 (I
> already did some convergence studies in another code).
> A example of an input is attached.
> This seems to be a problem for the code, as when I go higher than about
> 500 bands, I get the ¨error computing cholesky¨, which means the
> diagonalization fails.
>
> I read a lot of different topics in the mailing list reporting this
> problem, with various solutions such as :
> - parallelization on bands
> - CG diagonalization
> - bigger ¨diago_thr_init¨ (even if I need to be quite precise in the end)
> - beginning from a previous calculation with ~500 bands.
>
> I tried different things and it still didn't work. BTW, I know the
> calculation is possible, because I did it without problems in Abinit with
> the same parameters (Abinit seems to work differently).
>
> At this stage, I really don't know what I should do. Has someone already
> done successful calculations with so many bands ?
>
> Thanks in advance,
>
> Thierry Clette
>
>
>
>
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