[Octopus-devel] [Octopus-notify] svn commit: r3809 - in trunk: libxc src/h_sys src/include src/species src/sternheimer src/xc by marques

[Miguel Marques]

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  Hi Xavier,

> When I put back single precision I didn't manage to pass many tests, 
> besides the reduced precision we have in the code many places where we 
> check for values like 1e-12, 1e-14, etc., in single precision this 
> conditions can never been fullfilled and can cause problems.

I understand that. However, I am getting NaN and segfaults in some tests
in single precision. And this is a problem...

> I have been thinking about this and i think that in single precision mode 
> we should have only the wavefunctions in single precision and the rest of 
> the variables in double precision.
> 
> There are other variables we should always keep in single precision, like 
> m%x, the exp(ikr) phase and op%w_re for curvilinear coordinates.

I probably agree with you. I say probably, because I am not sure if
there is a clear speed gain (memory yes) from doing it. So, I tend to
look at the single precision code more like a toy to have around to try
out things (like CUDA). I am not sure it if deserves the effort to do it...

Concerning libxc in single precision, I was more thinking about people
like Andrea Marini that has most of his code in single precision. I
guess that for him (or someone else) libxc in single precision can be an
advantage...

> Does this commmits mean that Hugo will start to work in the cuda thing?

He did not answer my last email. The graphics card is apparently
working. I will try to write to him again...

  cheers,
  m.

- --
Dr. Miguel A. L. Marques
marques at tddft.org

Laboratoire de Physique de la Matière Condensée et Nanostructures
(LPMCN) - Université Lyon I
Bâtiment Brillouin, Domaine scientifique de la DOUA
69622 Villeurbanne Cedex
Tel +33 (0)4 72448187
Fax +33 (0)4 72432648
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