[CP2K:8241] Random number seed for Langevin MD

[Matthias Krack]

Hi Valentin

I have added a keyword SEED in the section &SUBSYS. That SEED keyword 
expects exactly 1 or 6 valid integer values as argument which define the 
initial seed(3,2) array for the Wiener process (a single argument value is 
replicated).
Please, check and provide feedback.

Matthias

On Friday, 14 October 2016 12:18:52 UTC+2, Ole Schütt wrote:
>
> Hi Valentin, 
>
> I opened a ticket at sourceforge for this. 
>
> -Ole 
>
> On 2016-10-13 19:19, Valentin wrote: 
> > Hi, 
> > 
> > my post concerns the problem that the value of the global seed does 
> > not affect the initialization of the parallel random number generator 
> > that is used for the Wiener process in the Langevin ensemble. For cp2k 
> > version 4.1_, _the first particle-specific seed is set in line 95 of 
> > _motion/wiener_process.F_ by calling _next_rng_seed()_ without 
> > arguments, thus resulting in 12345.0. 
> > 
> > I observed (using version 2.4) that setups that differed only in their 
> > initial velocities showed strong correlations among each other in 
> > their dynamics after a short time, which I would attribute to the 
> > noise term being de facto not random. 
> > 
> > A similar issue for MC calculations has been posted in this forum 
> > before (subject "Seed numbers bug in MC") and the problem has been 
> > solved in version 4.1 by specifying 
> > _last_rng_stream=force_env_1%globenv%gaussian_rng_stream_. Could you 
> > fix this problem for the Wiener process as well? 
> > 
> > Thanks, 
> > Valentin 
> > 
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