On Sunday 23 February 2003 04:41, Jeffrey B. Layton wrote:
> Tim Prince wrote:
> >In my experience,
> >'mpirun -np 2' on a single CPU P4 increases throughput by about 10% from
> > -np 1, but that gain doesn't hold up for scaling to a large cluster with
> > simple interconnects.
>
> Tim,
>
> My experience agrees with yours. When I ran the NASA Parallel
> Benchmarks on a Xeon cluster with even plain Fast Ethernet, it
> was always faster to turn off HT (we did it at the kernel level and
> at the BIOS level) These results are also supported by the following:
>
> http://computational-battery.org/Maskinvare/Hyperthreading.html
>
Apparently, those results were obtained with an early Xeon model with small
cache. Not that I dare to judge the issue, but results like this, where
simply turning on HT hurts performance, have sometimes been traced to errors
in the BIOS.
> Jeff
--
Tim Prince
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