> > Robert HYATT wrote:
> > >
> > > I ran the matrix multiply benchmark... with 1, 2, 3 and 4
> > > processors.
> > >
> > > The numbers I got were 52 seconds, 59 seconds, 66 seconds and 73 seconds
> >
> > Hmmm... with four cpus the benchmark took 11 sec more then with 1 cpu ??
> >
> > One might suppose you meant the times to be :
> >
> > 52/1 1 cpu
> > 59/2 2 cpu
> > 66/3 3 cpu
> > 73/4 4 cpu
> >
> > Cheers...
>
> Umm.. I believe the difference is 23 seconds and I would imagine it to
> be:
>
> 52 4 cpu
> 59 3 cpu
> 66 2 cpu
> 73 1 cpu
>
> But I could be wrong. ;)
>
No... the intent is to measure memory conflicts between the processors,
since the PC bus is not exactly blazingly fast. I ran the same identical
program one time, and it took 52 seconds. I ran two copies at the same
time, and the time went up, reflecting the memory bottleneck. It gives
a good idea of worst-case scaling for non-cache-friendly applications.
reasonable programs (which don't use 40mb arrays without a good blocking
algorithm) don't see this degradation...
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