topic Hyperthreading in dual-dual processor in Intel® Moderncode for Parallel Architectures

Hyperthreading in dual-dual processor

mattsdad — Thu, 05 Apr 2007 17:45:45 GMT

I am running an extreemly CPU intensive multi-body simulation which lend itself nicely to parallel processing. We have run several tests with the same simulation using a single-threaded compilation and a multi-threaded compilation. We have run the same simulation with the hyper-threading on and off. Here are the results:

The 12-body simulation on the dual-dual core Xeon machine runs about 70% faster when using the multi-threaded compilation compared to the single-threaded compilarion.

When we turn hyper-threading on, the execution of the multi-threaded compilation slows down about 15%. In this CPU intensive simulation, the 8 processor threads fight for CPU time and only average about 50% CPU time for each hyper-thread. With the hyper-threading off, the same simulation uses all four CPUs at almost 100% throughout the simulation.

So, we are are turning hyper-threading off because most of our processor time is spent running these CPU intensive simulations.

Re: Hyperthreading in dual-dual processor

TimP — Thu, 05 Apr 2007 18:56:34 GMT

Memory contention seems a more likely reason for low CPU utilization with increased number of threads. Several factors could be involved, including which OS you use.

Re: Hyperthreading in dual-dual processor

mattsdad — Mon, 09 Apr 2007 17:06:19 GMT

There is no question or problem here. I was only providing the data so others could use this data point in their evaluations. Maybe encourage checking the speed with and without hyper-threading for their own programs.