Octave 3.0.1 plotting is very slow

[Joerg van den Hoff]

On Tue, Jun 03, 2008 at 11:10:52AM +0200, Alakazam wrote:
> >>   - What machine are you running octave on ?
> > PPC Powerbook 1.5 GHz 2 GB
> 
> Which explains why plotting takes ~20s for you, and ~10s for me.
> 
> >>   - What version of Mac OS X are you running ?
> > 10.5.11
> 
> Is that 10.4.11 or 10.5.3 ? Anyway, this obviously does not change  
> anything, since we obtain similar results on the performance tests.
> 
> > Here are some more test results from running this program:
> > The setup is this, run only once per session:
> >   x = [1:100000];
> >   y = cos(x);
> >
> > The timed part is this:
> >   t = time(); plot(x, y); time() - t
> >
> > which reports an answer (call it t1) some time before the plot
> > appears (and at which time the prompt returns)--the latter time I
> > time on my watch call t2. In all cases the plot was run at least once
> > before timing it.
> 
> This is the same test I was running, so no problem here.
> 
> > Here are some results for t1 and t2 for various versions which are:
> > 2.1.71 downloaded last year from http://hpc.sourceforge.net
> > 3.0.1  downloaded today from http://hpc.sourceforge.net
> > 3.0.1  installed by Macports a few days ago
> >
> > Octave version    Output device   t1        t2
> > ==================================================
> > Macports 3.0.1    Aquaterm        0.64575   22
> > Macports 3.0.1    X11             0.41969   22
> > HPC      2.1.71   Aquaterm        2.7057    4
> > HPC      2.1.71   X11             N/A; uses Aquaterm
> > HPC      3.0.1    Aquaterm        0.62115   22
> > HPC      3.0.1    X11             N/A; defaults to Terminal.app
> >
> > FWIW, Activity Monitor reports high CPU usage from gnuplot while
> > waiting for the plots to appear.
> 
> So it would seem the problem may not be with the octave compilation  
> options, but indeed with the octave<->gnuplot interaction.
> 
> Do any macports users still have old octave2.9s (or, less likely,  
> octave2.1s) installed (via macports) ? Would you be willing to run the  
> quick aforementioned tests to check precisely when the problem may  
> have appeared ?

hi,

if it helps:

with  

GNU Octave, version 2.1.71 (powerpc-apple-darwin).

and

G N U P L O T Version 4.0 patchlevel 0

I get t = 1.7 sec (with a 2 GHz G5 under X11)


regards,

joerg

> 
> Reading
> 
> > http://www.gnu.org/software/octave/NEWS-3.html
> 
> I see that octave 3 (and 2.9) have introduced may changes to the  
> graphics backend, in particular to the way data is output to gnuplot :
> 
> > Octave now sends data over the same pipe that is used to send  
> > commands to gnuplot. While this avoids the problem of cluttering / 
> > tmp with data files, it is no longer possible to use the mouse to  
> > zoom in on plots. This is a limitation of gnuplot, which is unable  
> > to zoom when the data it plots is not stored in a file. Some work  
> > has been done to fix this problem in newer versions of gnuplot (>  
> > 4.2.2). See for example, this thread on the gnuplot development list.
> 
> 
> I think it would be best to take this issue to the octave team, and  
> see if they can reproduce the problem (on other platforms even ?) or  
> know where it might come from.
> 
> You may also want to check the different gnuplot versions used by  
> these octave versions ; maybe changes on that end might also influence  
> the plotting performance.
> 
> Regards,
> -- 
> Alakazam <alakazam at melix.net>
> 
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