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

From: Ian McCallion
Subject: Re: Perfromance problem running multiple copies of Octave on a multicore processor
Date: Thu, 10 Dec 2015 20:25:28 +0000

On 10 December 2015 at 15:13, Olaf Till <address@hidden> wrote:
> On Thu, Dec 10, 2015 at 01:46:53PM +0000, Ian McCallion wrote:

> Since you are using Windows, I couldn't check if your procedure indeed
> provides the same library to both Octave versions. You seem to assume
> that Octave uses the .dll version that is in the same directory as its
> own executable file;

It's not required to be so by windows, but it is not an assumption
either. If I delete libblas.dll Octave does not start up.

> I have no notion if this is the case in
> Windows. But the point is that indeed physically identical blas
> library files have to be used by both Octave versions for testing. I
> still suspect different libraries could have been used.

Suspect no longer:-)

However the versions of lapack are different. I will try doing the
same with lapack as I'm doing with blas.

> I didn't run your code, but you should not measure the duration of
> only the first process (in perf2), but of all parallel processes
> But I daresay the outcome will probably not be
> different.

I timed within the subprocesses to avoid the process start/stop
overhead. I checked all processes take about the same time, but on
windows fprintf interleaves at the character level sometimes making
deciphering the output difficult, which is why I only display the
results from process 1. (I would have output to files and merged the
results in perf1 if it had been necessary)

Cheers... Ian

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