[Octave-bug-tracker] [bug #57279] Slow plotting of multiple lines

[Milan]

URL:
  <https://savannah.gnu.org/bugs/?57279>

                 Summary: Slow plotting of multiple lines
                 Project: GNU Octave
            Submitted by: mxarko
            Submitted on: Wed 20 Nov 2019 04:05:45 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
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: GNU/Linux

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Details:

Octave plotting became much slower since v. 4.2.2. I have four OS-es installed
- Linux Mint 19.2 Cinnamon (kernel 4.15), Debian 10.1 Cinnamon (kernel 4.19),
MX Linux 19 (kernel 4.19), Windows 10 - and installed Octave on all of them.
Corresponding versions are: Mint - 4.2.2, Debian - 4.4.1, MX - 4.4.1, Windows
- 5.1.0. When I run plotting test example (shown below) by "grafTs(35)" only
on Mint it takes less than 1 s to execute and on the other systems it takes
around 14 s. Moreover, if I input bigger argument, say 55, on Mint the time
remains small (around 0.5 s) and on the other systems it goes up to 50 s. It
doesn't make big difference if the graphics toolkit is Qt, Fltk or Gnuplot.
Just to be clear: I measure the time not for the first run, i.e. the first
figure window, but for the runs from the second onwards.

These are pretty fresh installations, both the OS-es and Octave, for which I
didn't install any additional packages. But I did install the recommended
packages.

For testing purpose, I installed Octave 5.1.0 on Mint via Flatpak, and it is
slow like the other newer versions, from 4.4.1 onwards. Until now I didn't
find the way to revert to the original 4.2.2 installation, because now, after
purging the Flatpak one, even 4.2.2 is slow. But it is another problem, which
I don't observe here.

Is there a solution, to bring the speed of plotting in the newer versions of
Octave to the one in 4.2.2, I primarily mean for Linux? And will OOTB plot in
the following versions of Octave again be as fast as it once was?


function grafTs(k)
hf=figure;
ha=gca;
axis auto
axis equal
hold on
set(hf,'Renderer','painters')
cx=zeros(3,1e5);
cy=cx;
%k=55%;125%
e=[1;1;1];
s=sqrt(3)/2;
tx=[0;1;.5];
ty=[0;0;s];
b='c';
o=0;
for x=0:k-1
  for y=0:k-1-x
    o=o+1;
    cx(:,o)=(x+y/2)*e+tx;
    cy(:,o)=s*y*e+ty;
end,end
cx=cx(:,1:o);
cy=cy(:,1:o);
tic
plot(cx,cy,b,'Parent',ha)%fill
toc






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