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

[Milan]

Follow-up Comment #5, bug #57279 (project octave):

I have some new interesting findings. When I started this topic, Octave 4.2.2.
had plotted fast. After my activities which I exposed I didn't manage to have
it plot fast again. It had been very strange to me. Now I think that those my
changes of the system accidentally took place in the same time as some change
in Octave's behaviour, so Octave wouldn't plot fast any more even if I had not
touched it. I don't know what caused that change, probably some change in the
OS's behaviour due to updates. The fact that Octave 4.2.2. doesn't plot fast
any more even on another PC, also with Linux Mint, which I haven't messed with
in the meantime, supports that assumption.

Anyway, now I find that Octave 4.2.2. fills polygons fast, although it plots
slow! I modified my test program, so it accepts even the second argument,
which has logical meaning: apply "plot", not "fill". I measured plotting and
filling of Octave 5.1.0. via Flatpak and 4.2.2. on Mint 19.3 Cinnamon and of
Octave 4.4.1. on MX-19 Linux, all in VirtualBox.

New test program (0 means "fill"):

function grafTs(k,p)
hf=figure;
axis auto
axis equal
hold on
set(hf,'Renderer','painters')
cx=zeros(3,1e5);
cy=cx;
%k=55%;125%
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+=1;
    cx(:,o)=x+y/2+tx;
    cy(:,o)=s*y+ty;
end,end
cx=cx(:,1:o);
cy=cy(:,1:o);
tic
if p
  plot(cx,cy,b)
else
  fill(cx,cy,'w','EdgeColor','g')%fill%plot
end
toc


Octave 4.2.2. on Mint plotting and filling times:

>> grafTs(35,0)
Elapsed time is 0.107815 seconds.
>> grafTs(35,0)
Elapsed time is 0.0381899 seconds.
>> grafTs(35,0)
Elapsed time is 0.0344501 seconds.
>> grafTs(35,1)
Elapsed time is 20.0317 seconds.
>> grafTs(35,1)
Elapsed time is 21.6269 seconds.
>> grafTs(35,1)
Elapsed time is 22.7793 seconds.
>>


Octave 5.1.0. via Flatpak on Mint:

>> grafTs(35,0)
Elapsed time is 34.8323 seconds.
>> grafTs(35,0)
Elapsed time is 34.2146 seconds.
>> grafTs(35,1)
Elapsed time is 27.41 seconds.
>> grafTs(35,1)
Elapsed time is 28.1357 seconds.
>>


Octave 4.2.2. on Mint, after uninstalling 5.1.0. and reinstalling (maybe it is
interesting that the results are slightly different than at first
installation):

>> grafTs(35,0)
Elapsed time is 0.047008 seconds.
>> grafTs(35,0)
Elapsed time is 0.0826879 seconds.
>> grafTs(35,1)
Elapsed time is 15.3278 seconds.
>> grafTs(35,1)
Elapsed time is 15.9453 seconds.
>> grafTs(35,1)
Elapsed time is 16.7367 seconds.
>>


Octave 4.4.1. on MX:

>> grafTs(35,0)
Elapsed time is 15.117 seconds.
>> grafTs(35,0)
Elapsed time is 16.037 seconds.
>> grafTs(35,0)
Elapsed time is 15.8229 seconds.
>> grafTs(35,1)
Elapsed time is 18.9274 seconds.
>> grafTs(35,1)
Elapsed time is 19.4115 seconds.
>>


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