Re: Octave-gui graphics problems

[Tatsuro MATSUOKA]

> From: Vic Norton 

> To: octave-maintainers 
> Cc: Sebastian ; Parsiad Azimzadeh 
> Date: 2016/6/13, Mon 06:29
> Subject: Re: Octave-gui graphics problems
> 
> I’m attaching a revised, graphic-testing script: qtbug.m
> It along with the corresponding README.txt file are contained in the
> following archive.
>     
> 
> 
> This is not a terribly complicated situation. We are talking about a
> relatively simple, nonlinear map, which maps 3-dimensional space into
> 2-dimensional space and folds everything over the image of a "critical
> line". The critical line is the line on which the rank of the
> derivative of the map collapses to 1.
> 
> The only complication is that the source 3-dimensional space is an
> affine subspace of R^253, the space of all possible adjusted closing
> prices of financial securities for the 253 market days from 2013-12-31
> to 2014-12-31 inclusive.
> 
> My script, qtbug.m, simply shows the images of a bunch randomly
> generated R^253-points near the critlcal line. This script generates
> 2*nR random points, e.g., nR = 10000, 15000, 30000, near the critical
> line; with delta = 0.10, 0.12, 0.15 specifying the closeness of the
> points to the line (the smaller the delta the closer the points). It
> then plots the image of each generated point that lies within the
> clipping bounds
>      13.5 <= e <= 14.1 and 2.6 <= sig <= 2.9.
> 
> The computations in qtbug.m are pure numerical linear algebra. Octave
> has no problems with these computations. But displaying the results
> presents significant problems.
> 
> The qtbug.m script works fine in octave-gui when
>   octave> graphics_toolkit gnuplot
>   octave> setenv GNUTERM qt
> are set, but, on my system,
>   octave> graphics_toolkit qt
> produces seriously bad graphical results, and
>   octave> graphics_toolkit fltk
> simply crashes Octave.
> 
> I am working on an iMac, running OS X 10.11.5, and I'm using the latest
> homebrew version of Octave. As far as I can tell from participants on
> this list, the graphical problems of octave-gui are not just an
> artifact of my system. But I am a mathematician, not a computer
> software specialist. I don't know what is causing the problems or how to
> fix them. I can just point out that the problems exist and leave it at
> that. And perhaps my script will help someone fix these problems.
> 
> Here are some rough elapsed time statistics (typically upper bounds)
> from experiments with qtbug.m on octave-gui
>   gnuplot-qt
>     nR = 10000, mean = 0.32 sec, stdev = 0.02
>     nR = 15000, mean = 0.39 sec, stdev = 0.02
>     nR = 20000, mean = 0.46 sec, stdev = 0.02
>     nR = 25000, mean = 0.52 sec, stdev = 0.01
>     nR = 30000, mean = 0.59 sec, stdev = 0.01
>   qt
>     nR = 10000, mean = 0.36 sec, stdev = 0.03
>     nR = 15000, mean = 0.40 sec, stdev = 0.01
>     nR = 20000, mean = 0.46 sec, stdev = 0.02
>     nR = 25000, mean = 0.56 sec, stdev = 0.04
>     nR = 30000, mean - 0.62 sec, stdev = 0.04
>   fltk
>     nR = 10000, crashes for this and any other nR
> 
> What do the graphics look like?
>   gnuplot-qt  - great! 3 illustrative PNGs are attached
>   qt    - lousy on my system
>   fltk  - sometimes a bad figure will come up before the crash
> 
> Attached PNGs: This is the way things should look (from gnuplot-qt).
>   labeling scheme:  qtbug_gnuplot-qt_nR.delta.png
>     qtbug_gnuplot-qt_10000.100.png (61.0 KB)
>     qtbug_gnuplot-qt_15000.120.png (69.9 KB)
>     qtbug_gnuplot-qt_30000.150.png (80.4 KB)
> When delta = 0.100 the random points hug the critical line.
> When delta = 0.150 the points spread more away from the critical line.
> When delta = 0.120 we are between these two parameters.
> In all cases the random points cluster at the critical line from above.
> 
> A final note.
> F154 and X represent the historical performance of two unattended
> investment portfolios over 2014. The bogus portfolio XX and the false
> efficient frontier are what MATLAB would generate from the same data.
> Past history may not be an indicator future performance, but actual
> history has got to be better than some numerical artifact reflected
> off the back wall of Plato's cave.
> 
> Regards,
> 
> Vic
> 
> P.S. I’ve tried to include informative notes in my qtbug.m script.


I think that this topic is better to move to the bug tracker 
because your posts have pointed out some bugs in current octave.

Tatsuro