[gmx-developers] reproducability of md sims

[Carsten Kutzner]

Hi,

On 30 Nov 2014, at 11:17, Berk Hess <hess at kth.se> wrote:

> Hi,
> 
> There is documentation on this somewhere.
> Even when running with MPI and/or OpenMP simulations should be reproducible when ran on an identical run 
But reductions of several summands into a sum do not yield a bit-identical result across runs.
Therefore I think at least with MPI and/or OpenMP we will never get bit-identical 
trajectories unless the order of summation is fixed somehow for such operations.

Best,
  Carsten


> setup. The only things that usually matter, and which -reprod should turn off, are dynamic load balancing and FFTW kernel choice by timing.
> You can mail me your tpr and I can have a look.
> 
> Cheers,
> 
> BerkOn Nov 30, 2014 9:05 AM, David van der Spoel <spoel at xray.bmc.uu.se> wrote:
>> 
>> Hi, 
>> 
>> I'm trying to test reproducibility of simulations of liquids. The 
>> simulation systems are flexible (no constraints) and run with the 
>> -reprod flag, starting from the same tpr, on a single core. However 
>> after a few hundred fs the energy starts to diverge. 
>> 
>> Are there factors impacting the reproducibility that are not controlled 
>> by the -reprod flag? 
>> 
>> -- 
>> David van der Spoel, Ph.D., Professor of Biology 
>> Dept. of Cell & Molec. Biol., Uppsala University. 
>> Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. 
>> spoel at xray.bmc.uu.se    http://folding.bmc.uu.se 
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