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[lammps-users] A weird bulk drift and a overestimated MSD at GPU run.
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[lammps-users] A weird bulk drift and a overestimated MSD at GPU run.

From: ­조유환(공과대학 기계공학과) <mangoman@...5003...>
Date: Mon, 17 Jul 2017 17:42:20 +0900

To whom may help to solve my problem.


I have been run a series of test for the GPU package of LAMMPS.

Everything was fine a few days ago,

the calculation speed is amazing and the accuracy also is acceptable.

But now, I faced a problem. 

In some case, the result of GPU run is dubious in case of MSD(mean square displacement) and a weird drift of atomic bulk at the same time.

Comparing with a CPU run result, it usually has a 10~100 times larger MSD, also, in case of the CPU run, there is no bulk drift motion. 

I do not paste my script in here for now, but these job is related to annealing of liquid-Si.

And the most unaccountable thing is, a script, which do a melting of crystalline-Si, do not have such problem. 

* MSD is fine and there is no bulk drift motion. 
* An interatomic potential & system size are equal in the both cases.
* The script regarding melting is quite similar to the annealing one, I made the annealing one by modifying and adding a few sequence on the melting script.

It looks like there is some error or an important missing regarding GPU run for me.

Is there any related experience for GPU run ? (my current Lammps version is 31Mar17.)

Any comment will be helpful to figure out what is going on. 

Thank you for your help.