Octave 3.0.1 plotting is very slow

[Alakazam]

Hi !

On 30 mai 08, at 06:41, Jerry wrote:

> I noticed that plotting with the new Octave version 3.0.1 on Macports
> is very slow compared to older versions of Octave, e.g. 2.1.71. In
> the old Octave, small plots appear instantaneously, probably before
> the Return key hits its stop. In Octave 3.0.1, there is a lag of
> about a second--enough to be slightly annoying. On larger plots, the
> problem gets much worse. Plotting a 100,000 point vector on old
> Octave takes 3 seconds but on Octave 3.0.1 it takes 21 seconds.
>
> I suppose this is something that I should take up with the Octave
> people but I thought I'd tweak this list and the maintainer just in
> case it is something obviously wrong with this particular version.

Let me start with my (quick) tests :

> octave:1> t = time(); x = [1:100000]; y = cos(x); plot(x, y); time()  
> - t
> ans =  0.29453

But as you have noted, the graphic only appears after several seconds  
(~10s on my Nov '07 Mac Book).

So octave still manages the points very fast, but the graphics backend  
(X11 GnuPlot) seems to lag a bit.

If my example is not valid, and doesn't illustrate your problem  
correctly, could you give some reduction cases please ?

I also have a couple of questions which might help understand the  
cause of the problem.

   - What machine are you running octave on ?
   - What version of Mac OS X are you running ?
   - How did you compile octave 2.1 ?
   - What graphics backend does octave 2.1 use for plotting ?

My guess would be that your octave 2.1 doesn't use GnuPlot in the same  
way as the macports version of octave 3.0.

This might be fixable by changing configure/build options, though. If  
we reduce the problem to the graphics backend, as I suspect is the  
case, then we can look if the graphics backend has changed for all  
octave3.0s from octave2.1s, or if this is indeed configurable, and it  
is possible to get the old plotting infrastructure back.

> BTW, the first time or two that I tried to make a plot (simple, like
> plot(x, y)) with the newly installed version of Octave from Macports,
> it failed completely and emitted about 10 lines of Octave-related
> errors. One or two restarts resulted in plots being made, but slowly,
> as noted above.


Are you able to reproduce the errors, or at least do you still have  
the corresponding octave output ? Did anything (files, paths, relaunch  
shell) change between restarts ? Are you talking about Mac OS X  
restarts, or simply exiting octave and launching it again immediately ?

Regards,
-- 
Alakazam <alakazam at melix.net>