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[Octave-bug-tracker] [bug #45890] Sparse A*x and A+B are a bit slow

From: Marco Caliari
Subject: [Octave-bug-tracker] [bug #45890] Sparse A*x and A+B are a bit slow
Date: Wed, 15 Aug 2018 16:25:30 -0400 (EDT)
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0

Follow-up Comment #13, bug #45890 (project octave):

@Rik: I do not see your bm_sparse.m, but I run the original test. I do not see
at all the problem with A'*x. My A'*x is faster than A*x, as in the original
report. In general, my results agree with the original report. About A+B, I
thought it was due to multithreading in matlab, but this is not true. That is,
matlab is faster also forcing it to use a single thread (matlab
-singleCompThread). To summarize:

octave:7> bm_sparse
GNU Octave Version: 5.0.0 (hg id: 8df89a90fdba+)
GNU Octave License: GNU General Public License
Operating System: Linux 4.4.0-131-generic #157~14.04.1-Ubuntu SMP Fri Jul 13
08:53:17 UTC 2018 x86_64
no packages installed.

N=1000000 NNZ=20000000 NRUNS=5
 sparse: 3.138752 (0.058661)
 2*A   : 0.215353 (0.006110)
 A'    : 2.566570 (0.058285)
 A+B   : 0.744875 (0.027312)
 A*x   : 0.420970 (0.012134)
 A'*x  : 0.194607 (0.009360)

and matlab -singleCompThread

MATLAB Version: (R2017b)


N=1000000 NNZ=20000000 NRUNS=5
 sparse: 3.604938 (0.018558)
 2*A   : 0.149879 (0.001227)
 A'    : 2.547904 (0.097282)
 A+B   : 0.378851 (0.001527)
 A*x   : 0.243945 (0.004315)
 A'*x  : 0.177749 (0.007021)


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