Re: Perfromance problem running multiple copies of Octave on a multicore processor

[Olaf Till]

On Mon, Nov 30, 2015 at 11:39:02PM +0000, Ian McCallion wrote:
> ...
> As far as I can see this proves that there is some serialisation going
> on in Octave 4.0.0 that was not going on in Octave 3.8.2. It sounds
> like a bug (system wide serialisation protecting a local resource?).

Sounds improbable.

> Has anyone got any suggestions for a workaround, alternative
> explanations for the cause of the problem

An explanation could be using up the common L2 cache of the processor
cores, so that they must share the main memory bus. Maybe some
calculation in the newer Octave is spread over a larger memory area.

> or other tests I can run to
> elucidate the problem.

It could be useful to find the smallest possible unit (e.g a native
Octave function, or a builtin function called by it) which shows your
problem.

Your idea with different BLAS libraries seemed good to me, make sure
you tested this influence correctly.

Olaf

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