[Pw_forum] bug in mm_dispersion.f90

[Stefano de Gironcoli]

Hi , thank you for your contribution.
Have you tested the 4.1 version and verified that it has a bug ? I mean, 
have you done a parallel calculation with and w/o pools and seen that 
they give different results ?  Moreover, have you tested your modified 
version and seen that it is working correctly ?
do you have simple example where this can be seen ?
best regards,
  stefano de Gironcoli - SISSA and DEMOCRITOS

Javier Fuhr wrote:
> Hi,
> I think I've found a bug in the calculation of the dispersion 
> energy/force/stress when doing a parallel calculation with more than 
> one pool. In mm_dispersion.f90, the sum between the processes is only 
> done intra_pool but not inter_pool.
> Here is a diff between the version 4.1 and a possible corrected one 
> (I'm not an expert in the paralelization of QE...):
> -----------------------------
> 261c261
> <     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm
> ---
> >     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm, 
> inter_pool_comm
> 362a363
> >       CALL mp_sum ( energy_london , inter_pool_comm )
> 377c378
> <     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm
> ---
> >     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm, 
> inter_pool_comm
> 503a505
> >       CALL mp_sum ( force_london , inter_pool_comm )
> 519c521
> <     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm
> ---
> >     USE mp_global,    ONLY : mpime , nproc , intra_pool_comm, 
> inter_pool_comm
> 660a663
> >       CALL mp_sum ( stres_london , inter_pool_comm )
> -----------------------------
>
> Regards,
> Javier
>
> -- 
> Dr. Javier Daniel Fuhr
> Grupo Física de Superficies - Div. Colisiones Atómicas
> Centro Atómico Bariloche
> Bariloche - Argentina
> TE : ++54 2944 44 5100  Int. 5524
> FAX: ++54 2944 44 5299
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