[Octave-bug-tracker] [bug #48085] Slow solving simultaneous equations by LU decomposition for octave 4 on windows

[Tatsuro MATSUOKA]

Follow-up Comment #10, bug #48085 (project octave):

I have built octave-3.8.2 by myself on Ubuntu 14.04 LTS amd64 to ensure that
octave binaries use the same versions of LAPACK (3.5.0) and
BLAS(1.2.20110419).

I have executed test on comment #7 on 3.8., 4.0.2 and
4.1.0+(21793:50f49dcae277).

3.8.2

Simple left division
Elapsed time is 0.351762 seconds.
LU decomposition
c=P*B
Elapsed time is 8.79765e-05 seconds.
y=L\c
Elapsed time is 0.0066781 seconds.
x=U\y
Elapsed time is 0.00686312 seconds.


4.0.2

Elapsed time is 0.351755 seconds.
LU decomposition
c=P*B
Elapsed time is 8.01086e-05 seconds.
y=L\c
Elapsed time is 0.0207329 seconds.
x=U\y
Elapsed time is 0.0217681 seconds.


4.1.0+

Simple left division
Elapsed time is 0.349451 seconds.
LU decomposition
c=P*B
Elapsed time is 8.98838e-05 seconds.
y=L\c
Elapsed time is 0.0207131 seconds.
x=U\y
Elapsed time is 0.0217669 seconds.


It seems that slowness of left division by triangular matrix seem not to be
related by LAPACK and blas versions. 


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