Re: Multithreading question

[Marcus G. Daniels]

> What I've seen about hyperthreading suggests that you'll probably get some 
> performance boost without special libraries; how much is never generalizable in 
> these cases (hyperthreading is optimized to accelerate Windows API threads, not 
> necessarily 3rd party apps).  Whether you can get more boost with a 
> hyperthread-aware library I dunno, but I would certainly expect so.
A hyperthreaded Pentium 4 system will look like two Pentium 4s.   
Whether the system has the performance of a dual processor machine 
depends on whether or not one thread has inherent waits from outside, 
such that the other can be freed up to do work.  If the two processors 
are `cooperating' on a problem, there is the possibility of super-linear 
speedups because the two virtual CPUs share the same instruction and 
data cache, whereas two physical processors would not..  An example of 
such an opportunity (very weakly) might be a Java/Swarm model where the 
Swarm  simulation filled up a buffer and a Java thread took 
responsibility for emptying it (say, as a moving average datapoint).


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