Subject: Re: CPU usage

From: benne278 <benne278 ~~ umn.edu>
Date: Tue, 08 Feb 2005 19:10:17 CST

On 8 Feb 2005, Mark Mackey wrote:

> The benefit of HT is that if there is more than one process running, you
get
> slightly faster throughput than if HT was not enabled. Note that this
> benefit is generally only slight (5-10% max). 

I've seen increases in total work done of ~ 25%-30% on some higher-end two
processor Linux workstations.  I was pleasantly surprised by this result. 
But this was doing molecular mechanics calculations that easily fit in RAM.
 As you mentioned, having two QM jobs fighting for the scratch disk could
overwhelm this advantage.

Nevertheless, for anyone concerned about total job time, it's probably
worth running a test case of your own work with hyperthreading on.  It
might be worthwhile.  On the other hand, if you are in a queueing system
and you need accurate estimates of wall clock time for your jobs,
hyperthreading can be more trouble than it's worth even if your jobs get a
decent speed boost.

-Eric Bennett
Center for Drug Design
University of Minnesota