[Pw_forum] Energy variations in noncolin-constrain_total.in with OpenMP & MKL

[Paolo Giannozzi]

"configure --enable-openmp". Maybe it is not very visibile, but it is
documented, and listed among options if you type "configure --help"

Paolo

On Thu, Jan 28, 2016 at 1:25 PM, Reinaldo Pis Diez <
reinaldo.pisdiez at gmail.com> wrote:

> Dear Nick,
>
> How did you build the OpenMP version of QE? I was unable to find any
> reference to such a flavor for QE nor to the omp header in source
> files.
>
> Regards,
>
> Reinaldo
>
> Reinaldo Pis Diez
> PhD in Chemistry
> Principal Researcher - CONICET (Argentina)
> Associated Professor - UNLP (Argentina)
>
> On 01/27/2016 03:33 PM, Nick Wilson wrote:
> >
> >> On 26 Jan 2016, at 20:02, Paolo Giannozzi <p.giannozzi at gmail.com
> >> <mailto:p.giannozzi at gmail.com>> wrote:
> >>
> >>
> >>     One should obtain the same numbers - within the errors due to
> >>     roundoff, though -  in serial, OpenMP, MPI execution, and on
> >>     different machines, and with different compilers and
> >>     mathematical libraries.
> >>
> >>
> >> ... actually, only at exact convergence, at least when using
> >> default wavefunction initialization: small differences come from
> >> different randomization of atomic wavefunctions. These however
> >> disappear as convergence is made tighter (but sometimes they don’t
> >
> >
> > Thanks Paolo & Stefano, that’s very useful information.
> >
> > The convergence threshold was at 1.0e-9 and when I tightened it to
> > 1.0e-12 it improved the agreement significantly.
> >
> > Best regards,
> > Nick
> >
> >
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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