[Octave-bug-tracker] [bug #31305] slow contour plot

[David Bateman]

Update of bug #31305 (project octave):

                  Status:                    None => Need Info              

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Follow-up Comment #1:

Using __go_patch__ rather than patch will save the sending up of the listener
functions that mean that changes to the patch xdata etc affects the vertices
and faces variables. As the patch objects are wrapped in a contourgroup where
the user is supposed to change the variables, that seems pretyy save. Doing
that on my atom bring the execution time of contour(rand(15)) down from 8.3sec
to 3.5sec on my atom machine, which is nice but not enough.

I suppose we can do what is done in the scatter function to treat all the
patches with the same contourlevel as the same patch. However before doing
this it would be interesting the known the behavior of matlab in these case. I
suspect they also group contours in this manner. Could you run 

a=[-1,0,1,0,-1,0,1,0,-1];
[c,h]=contour(kron(a,a'),-0.75:0.25:0.75);
length(get(h,'children')

in matlab and tell me what it gives? If it plots a patch for each contour it
should give "87" as Octave currently does.

D.


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