[Octave-bug-tracker] [bug #61259] slow printing of images

[Fabio]

URL:
  <https://savannah.gnu.org/bugs/?61259>

                 Summary: slow printing of images
                 Project: GNU Octave
            Submitted by: efferre79
            Submitted on: Thu 30 Sep 2021 10:17:17 PM UTC
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: 6.2.0
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:

I am facing a performance issue when trying to export an image if the data
size is huge. The result is quite different when the figure is visible or not.
The exec time is independent of bitmap/vector output format.

I am using the qt toolkit but I have tried all toolkits with more or less the
same result. I have written the following test:


agt=available_graphics_toolkits;
x=linspace(1,2,1e6);
v={'on','off'};

for j=1:length(v)
    fprintf(1,'figure visibility is %s\n', v{j})
    figure(1,'visible', v{j})

    for k=1:length(agt)
        graphics_toolkit(agt{k});
        fprintf(1,'toolkit is %s\n', agt{k})

        clf
        plot(x,x)
        tic;print('test_large.png');et=toc;
        fprintf(1,'printing of png took %f seconds\n', et)
        tic;print('test_large.pdf');et=toc;
        fprintf(1,'printing of pdf took %f seconds\n', et)
    end
end


with 1e5 points:

figure visibility is on
toolkit is fltk
printing of png took 2.512742 seconds
printing of pdf took 2.580937 seconds
toolkit is gnuplot
printing of png took 2.556829 seconds
printing of pdf took 2.565509 seconds
toolkit is qt
printing of png took 2.447250 seconds
printing of pdf took 2.536983 seconds
figure visibility is off
toolkit is fltk
printing of png took 1.164396 seconds
printing of pdf took 1.251188 seconds
toolkit is gnuplot
printing of png took 1.195915 seconds
printing of pdf took 1.297156 seconds
toolkit is qt
printing of png took 1.207151 seconds
printing of pdf took 1.240340 seconds

with 1e6 points:

figure visibility is on
toolkit is fltk
printing of png took 43.931664 seconds
printing of pdf took 44.527668 seconds
toolkit is gnuplot
printing of png took 44.168895 seconds
printing of pdf took 44.763425 seconds
toolkit is qt
printing of png took 43.786862 seconds
printing of pdf took 45.107477 seconds
figure visibility is off
toolkit is fltk
printing of png took 11.101900 seconds
printing of pdf took 11.941227 seconds
toolkit is gnuplot
printing of png took 11.286645 seconds
printing of pdf took 11.907872 seconds
toolkit is qt
printing of png took 11.394462 seconds
printing of pdf took 11.821886 seconds

with 10e6 points:

figure visibility is on
toolkit is fltk
printing of png took 989.613597 seconds
printing of pdf took 1037.992974 seconds
toolkit is gnuplot
printing of png took 978.964138 seconds
printing of pdf took 940.796408 seconds
toolkit is qt
printing of png took 950.266446 seconds
printing of pdf took 1281.552140 seconds

figure visibility is off
toolkit is fltk
printing of png took 171.231403 seconds
printing of pdf took 183.784420 seconds
toolkit is gnuplot
printing of png took 171.192138 seconds
printing of pdf took 182.603688 seconds
toolkit is qt
printing of png took 208.856389 seconds
printing of pdf took 264.242813 seconds

Here for 1e6 and 10e6 points I have filtered out from the output the following
warnings:

GL2PS info: OpenGL feedback buffer overflow
warning: gl2ps_renderer::draw: retrying with buffer size: xxx B

where the buffer size is progressively increased (even many times for each
print() call) with the effect of taking more and more time for the execution




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