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Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0
From: |
Ian McCallion |
Subject: |
Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0 |
Date: |
Tue, 29 Sep 2020 18:12:38 +0100 |
On Tue, 29 Sep 2020 at 17:54, Ian McCallion <ian.mccallion@gmail.com> wrote:
>
>
>
> On Tuesday, 29 September 2020, Nicholas Jankowski <jankowskin@asme.org> wrote:
>>>>
>>>> Downloading Octave 5.2.0-64 bit executable from the official GNU Octave
>>>> website(https://www.gnu.org/software/octave/download.html#ms-windows) for
>>>> Win 10
>>>> Installing the same and checking with the default OPENBLAS library.
>>>> Assigning the value for the environment variable OPENBLAS_NUM_THREADS =
>>>> "the number of processors we need to utilize"
>>>
>>>
>>> The second step is not necessary. Otherwise yes.
>>>
>>> Ian
>>
>>
>> Do you mean the installing or assigning step?
>>
> My apologies. I was away from my desk any failed to give the question my full
> attention.
>
> Install ( of course), but the default installation does result in
> libopenblas.dll being copied to libblass.dll so that "checking with the
> default OPENBLAS library" is not necessary.
>
>> In my default config zip install, OPENBLAS_NUM_THREADS was empty. I set it
>> to different values from 1-4 since I have a 4 core machine, and didn't
>> notice any real difference running that test routine you posted. i extended
>> the 1e8 to 2e8 and 1e9 to get meaningful runtimes, but there seemed to be no
>> difference changing the value of that option. in all cases multiple cores
>> were taxed on execution. It's a managed machine so I don't have Process
>> Explorer to actually verify the thread count, so maybe other things are
>> happening that I'm not noticing.
>
>
> I have the same result. I have task manager and whatever the value of
> OPENBLAS_NUM_THREADS the execution time is the same and the cpu utilisation
> peaks at the same level so it would appear the environment variable is being
> ignored. I will investigate further as my system uses this, succesfully I
> believe!
Progress. It all comes flooding back to me now! You must set
OPENBLAS_NUM_THREADS before launching Octave, which is of course a
real pain and cannot surely be justified as you might actually want to
change the number of threads used. I Imagine the DLL is loaded at
Octave startup and the value of OPENBLAS_NUM_THREADS is read at that
time.
If you don't set OPENBLAS_NUM_THREADS the default is to use enough
threads to consume most the CPU fully, and on my system I get
>> tic; a=rand(10000); b=a*a;toc
Elapsed time is 13.0891 seconds.
setting OPENBLAS_NUM_THREADS=1 and then calling Octave:
>> tic; a=rand(10000); b=a*a;toc
Elapsed time is 42.447 seconds.
One way to set OPENBLAS_NUM_THREADS which avoid leaving the Octave
environment is:
>> setenv('OPENBLAS_NUM_THREADS','1')
>> system C:/Octave/Octave-5.2.0/octave.vbs
This launches a second copy of Octave with the first as parent hence
inheriting the environment variables.
Cheers... Ian
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, (continued)
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Ilaya Bharathi, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Nicholas Jankowski, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Ian McCallion, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Nicholas Jankowski, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Ilaya Bharathi, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Nicholas Jankowski, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Dmitri A. Sergatskov, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Markus Mützel, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Ian McCallion, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0, Nicholas Jankowski, 2020/09/29
- Re: Instructions for Installing BLAS and LAPACK library on Octave 5.2.0,
Ian McCallion <=