[gmx-developers] threads are now ON by default

[David van der Spoel]

On 2/12/10 5:32 PM, Sander Pronk wrote:
> Now that the last issues have been resolved with the threading code, thread-based parallelization has been turned on by default. To disable all the threading code, use
>
> --disable-threads.
>
> in configure, or turn the option GMX_THREADS off with ccmake.
>
> Running mdrun with just one thread (the default) is almost exactly the same as running it without threading code: the only thing that's different is that the few remaining global variables are protected by mutexes.
>
> Performance-wise mdrun runs very slightly faster with threads than with OpenMPI when Nthreads<=Ncores (and there is no other processes on the computer). When Nthreads>Ncores (or other processes are running), the thread code is much faster than OpenMPI, but the total runtime is still smaller than when Nthreads==Ncores.
>
> If there's any problems in getting things running, or with performance, I'd very much like to hear about it.
>
> Sander
>
>
Great work Sander!

What about the rumours that enabling hyperthreading gives you 
superscaling beyond Ncores?

-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se