yade-users team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

> I have i7 Intel processor wit 4 cores. But system sees it like 8-core
> machine because of HyperThreading.
> I have some problems with performance. When I start a simulation with
> about 1000 particles and default OMP_NUM_THREAD option, I have about
> 10-11iter/sec, what is extremely low.
> 
> When I start the same simulation with OMP_NUM_THREAD=4, I get the
> speed about 160-180 iter/sec.

Disable hyperthreading in BIOS and you will get at least 250/sec with
default (number of cores, i.e. 4) threads. HT gives you ZERO benefit for
number crunching (actually it hurts performance), it can only make
number of different processes (like typical desktop usage) run a little
faster, as one hyperthread can be run while the other one is waiting for
RAM. Read http://people.redhat.com/drepper/cpumemory.pdf for some
details.

Cheers, Vaclav