bugGNU Octave - Bugs: bug #45208, mxe-octave: compile with OpenBLAS...

 
 

bug #45208: mxe-octave: compile with OpenBLAS with LAPACK enabled

Submitted by:  Ceral Paquet <octavebugs>
Submitted on:  Fri 29 May 2015 02:01:57 AM UTC  
 
Category: Configuration and Build SystemSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Performance
Status: InvalidAssigned to: None
Originator Name: Open/Closed: Closed
Release: 4.0.0Operating System: GNU/Linux

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Tue 02 Jun 2015 04:50:22 PM UTC, comment #5:

Retagging release from 4.0.0-rc4 to 4.0.0.

John W. Eaton <jwe>
Project Administrator
Sun 31 May 2015 04:08:52 PM UTC, comment #4:

Closing bug report as invalid, if I'm reading correctly.

Mike Miller <mtmiller>
Project Administrator
Fri 29 May 2015 09:23:03 PM UTC, comment #3:

Ceral: Do not worry. Everyone makes mistakes, or gets
confused. Better to report what you find. At least then
it is likely that things will get clarified.

Michael Godfrey <godfrey>
Project Member
Fri 29 May 2015 07:58:07 PM UTC, comment #2:

OK well it appears I am the king of erroneous bug reports this week. Sorry about that :(

This is what I ran:

getenv('OPENBLAS_NUM_THREADS')
A=randn(4000);
tic;AA=A'*A;toc
tic;chol(AA);toc
tic;svd(A);toc

and these are the timings:

Compiled with NO_LAPACK=1 (current default in MXE)
-------------------------

>> getenv('OPENBLAS_NUM_THREADS')

ans = 1

>> A=randn(4000);
>> tic;AA=A'*A;toc

Elapsed time is 11.7313 seconds.

>> tic;chol(AA);toc

Elapsed time is 4.23956 seconds.

>> tic;svd(A);toc

Elapsed time is 60.8286 seconds.

>> getenv('OPENBLAS_NUM_THREADS')

ans = 2

>> A=randn(4000);
>> tic;AA=A'*A;toc

Elapsed time is 6.40621 seconds.

>> tic;chol(AA);toc

Elapsed time is 2.50854 seconds.

>> tic;svd(A);toc

Elapsed time is 47.2539 seconds.

Compiled with NO_LAPACK=0
-------------------------

>> getenv('OPENBLAS_NUM_THREADS')

ans = 1

>> A=randn(4000);
>> tic;AA=A'*A;toc

Elapsed time is 11.7115 seconds.

>> tic;chol(AA);toc

Elapsed time is 4.24126 seconds.

>> tic;svd(A);toc

Elapsed time is 60.4084 seconds.

>> getenv('OPENBLAS_NUM_THREADS')

ans = 2

>> A=randn(4000);
>> tic;AA=A'*A;toc

Elapsed time is 6.55407 seconds.

>> tic;chol(AA);toc

Elapsed time is 2.51173 seconds.

>> tic;svd(A);toc

Elapsed time is 46.6011 seconds.

Ceral Paquet <octavebugs>
Fri 29 May 2015 01:12:35 PM UTC, comment #1:

Can you post the test you used, so that it can also be tried on windows?

John Donoghue <lostbard>
Project Member
Fri 29 May 2015 02:01:57 AM UTC, original submission:

I noticed with some linear algebra methods that only 1 of my CPU cores was being used despite using Openblas and specifiying export OPENBLAS_NUM_THREADS=2.

A'*A uses both cores but chol, svd do not. Openblas provides some of these LAPACK functions.

I ran a little test with chol and svd and noticed they both run about 1.5 times faster with NO_LAPACK=0 in src/openblas.mk - both CPUs are used rather than only 1 when NO_LAPACK=1. I can't think of a downside.

Ceral Paquet <octavebugs>

 

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  • -unavailable- added by jwe (Posted a comment)
  • -unavailable- added by mtmiller (Posted a comment)
  • -unavailable- added by godfrey (Posted a comment)
  • -unavailable- added by lostbard (Posted a comment)
  • -unavailable- added by octavebugs (Submitted the item)
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    Follow 5 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Tue 02 Jun 2015 04:50:22 PM UTCjweRelease4.0.0-rc4=>4.0.0
    Sun 31 May 2015 04:08:52 PM UTCmtmillerCategoryNone=>Configuration and Build System
      Item GroupNone=>Performance
      StatusNone=>Invalid
      Open/ClosedOpen=>Closed

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