nemesis <nam### [at] gmailcom> wrote:
> > beta.30-rad1 on 4 cores:
> >
> > real 53.99
> > user 195.49
> > sys 0.11
> >
> >
> > beta.30-rad1 throttled to use 1 core only:
> >
> > real 292.78
> > user 292.48
> > sys 0.03
>
> Forgive my stupid ignorance, but shouldn't it be expected that usage of
> more cores to handle more threads separately and truly running in
> parallel would lead naturally to such boost in performance?  Isn't that
> what all this multicore hype is all about?

A multicore system is basically just a multiprocessor system, with the
processors placed on a single die to (a) reduce costs, (b) share more
components among the CPUs (e.g. cache) to reduce synchronization overhead, and
(c) speed up synchronization of the remaining components by reducing signal
path lengths.

The benefit, like in a multiprocessor system, is from no more than multiple
workers doing the same job. So if you have N processors, you'd expect a speed
gain of the factor N, minus some overhead work introduced by the
multithreading.

Look again at the figures above:

1 core  -> 293 seconds
4 cores ->  54 seconds

Either my math is rusty, or this is a speed gain by more than the number of
cores...

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