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

[Ian McCallion]

Hi Olaf and Mike,

Thank you both for your help. I have now worked out in more detail
what has been happening to cause anomalous performance between Octave
3.8.2 and Octave 4.0.0 in my signal processing system:

     Octave 3.8.2 and earlier releases, with the supplied openblas
     and lapack, only ever used a single thread, whether by design
     or accident and whatever value (or none) at all was set for
         OPENBLAS_NUM_THREADS

    This was changed/fixed in Octave 4.0.0.

I did not find any reference to this change in the documentation, and
it may be worth adding a few lines in news to explain this.

Cheers... Ian

On 10 December 2015 at 23:37, Ian McCallion <address@hidden> wrote:
> Hi Mike,
>
> On 10 December 2015 at 18:11, Mike Miller <address@hidden> wrote:
>> Are you using the 4.0.0 official binary?
>   Yes.
>> Which 3.8.2 binary are you using?
>   Not sure - it was a while ago.The binaries are timestamped
> 2014-09-04 20:15 and I downloaded the installer from the official
> site. I am pretty sure I redownloaded to get the second iteration of
> 3.8.2 when it appeared.
>
> Regarding controlling the number of threads used by blas and lapack:
> -  I have looked for references to OMP_NUM_THREADS in documentation
> and found nothing.
> -  I have tried setting OMP_NUM_THREADS environment variable inside or
> outside octave to no effect.
> Have mechanisms for controlling the number of threads used by openMP
> been changed somewhere in Octave lapack blas and openMP?
>
> Cheers... Ian