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

[Tatsuro MATSUOKA]

Follow-up Comment #11, bug #48085 (project octave):

I have built octave-3.8.2 on native windows using the same LAPACK (3.5.0) and
openblas (0.2.18) that are used for 4.0.2 and 4.1.0+.

And execute


Simple left division
Elapsed time is 0.0590401 seconds.
LU decomposition
c=P*B
Elapsed time is 0 seconds.
y=L\c
Elapsed time is 0.002002 seconds.
x=U\y
Elapsed time is 0.00100088 seconds.


Elapsed time for y=L\c and x=U\y on 3.8.2 is faster that those on octave 4
also on windows.

Thus this issue is not related to the LAPACK and blas version and seems to be
platform independent except for slowness of all left division on 4.1.0+ on
windows.

I propose that 
1. I will make a new file of bug tracker for slowness all left division on
4.1.0+ on windows 

and 

2. this tracker are kept for slow left division by triangular matrix on octave
4 (platform independent.)
  
The titles proposed are

1. Slowness of left division on 4.1.0+ on windows

2. Slowness of left division by triangular matrix on octave ver. 4

respectively.

I hope that someone improve the title because my English is poor.

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