[CP2K:8241] Random number seed for Langevin MD

[Ole Schütt]

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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