[gmx-developers] Re: threads are now ON by default

[Sander Pronk]

Threads are only on in the current git version - it's a feature currently under development. There's no thread support in the gromacs 4.0 releases.

BTW how big is your system? It might be too small to be reasonably parallelized. 
I've tested performance on a core i7 and got about 20% better performance with 8 threads vs. 4 threads with taskset 0xf.

Sander


On 6 Apr 2010, at 21:21 , Dinler Antunes wrote:

> 
> We are using an i7 920 processor to run Gromacs-4.0.7 with openmpi-1.4.1. The
> simulations run well using 4 threads (using "mpirun -np 4 mdrun...") but the
> performance is worse when we use 6 or 8 threads. Looking for some way to improve
> our performance we found out this forum and then started to try use threads
> without openmpi. We compiled gromacs again and used the command line as
> described here ("mdrun -nt 8..."), but the following error appears:
> 
> ------
> Program mdrun, VERSION 4.0.7
> Source code file: mdrun.c, line: 410
> 
> Fatal error:
> GROMACS compiled without threads support - can only use one thread
> ------
> 
> But in gromacs-4.0.7 threads are not supposed to be ON by default?
> 
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