[Pw_forum] Benchmarking QE 4.1

[Stefano Baroni]

just as a side note, the fact that subsequent SCF steps require less davidson iterations should be seen as an advantage (due to the use of smart iterative diagonalization techniques), rather than a disadvantage. I do not quite understand why you need so many k-points, given the symmetry of SrTiO3, and its insulating character ... SB
 
On Jan 21, 2010, at 2:26 PM, Lorenzo Paulatto wrote:

> On Wed, 20 Jan 2010 20:04:40 +0100, Marcos Veríssimo Alves  
> <marcos.verissimo.alves at gmail.com> wrote:
>  The time bewteen the end of
>> the initialization of the calculation (starting mode="from scratch")
>> and end of the first calculation step are much longer than the typical
>> times for the subsequent davidson diagonalization steps (between 4-5
>> times longer):
> 
> Dear Marcos,
> when performing the first diagonalization the initial trial wavefunctions  
> used by the algorithm are just a superposition of atomic wavefunctions,  
> which are only a very rough estimate of the eigenvaleus. On subsequent  
> steps the initial trial wavefunctions are the ones from the previous scf  
> step, which are usually quite a good estimate. If after finishing the  
> calculation you restart it from scratch, but setting startingwfc='file',  
> you should find that now the first diagonalization step is as fast as the  
> subsequent ones.
> 
> best regards
> 
> 
> -- 
> Lorenzo Paulatto
> 
> *** Note: my affiliation has changed! please send future
> correspondence to: <Lorenzo.Paulatto at impmc.upmc.fr> ***
> 
> post-doc @ IMPMC/UPMC - Université Paris 6
> phone: +33 (0)1 44 27 74 89
> www:   http://www-int.impmc.upmc.fr/~paulatto/
> 
> previously:
> phd student @ SISSA  &  DEMOCRITOS (Trieste)
> phone: +39 040 3787 511
> www:   http://people.sissa.it/~paulatto/
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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