[gmx-developers] Re: parallelization and accuracy

[Justin MacCallum]

Hi Frauke,

I would agree with what Anton and David have said. When I was hacking
the parallel version in I performed a check on a system that I the
results for, and the histograms produced by the serial and parallel
versions are almost identical.

Justin

> Dear all, dear Justin,
> 
> I tried to change the pull code of the 3.1.4 version to enable it to
> run in parallel. In principle it works, but the force I obtain starts to
> differ (by 10^-3 kJ/mol/nm) from a sequential run from the 5th integration
> step on. The force profiles of the seq. and parallel run finally diverge
> after several 100 steps.
> Any hint, what the reason might be for that? The only things I changed are
> to add the stuff for parallel runs to the list of variables the procedures
> of the pull code are called with (start, homenr, cr) and to restrict I/O
> to the master node (actually I just transferred all changes for parallel
> pulling of the cvs version into my code).
> 
> Thanks for all hints, which my mistakes might be.
> Cheers,
> Frauke