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

[Reinaldo Pis Diez]

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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