[Octave-bug-tracker] [bug #47052] Plotting many lines on a graph is slow

[Lachlan Andrew]

Update of bug #47052 (project octave):

                  Status:                    None => Patch Submitted        
             Assigned to:                    None => lachlan                

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Follow-up Comment #5:

Here is a patch ready for feedback.

Before:


octave:1> a = rand (48, 365);
octave:2> tic; for i = 1:100; plot (a'); end; toc
Elapsed time is 87.1696 seconds.
octave:3> tic; for i = 1:100; plot (a); end; toc
Elapsed time is 682.938 seconds.
octave:4> 


After:


octave:1> a = rand (48, 365);
octave:2> tic; for i = 1:100; plot (a'); end; toc
Elapsed time is 9.98498 seconds.
octave:3> tic; for i = 1:100; plot (a); end; toc
Elapsed time is 51.0427 seconds.


The optimizations are:
1. Call __go_line__ directly instead of calling line.m many times.  (This is
in bug_plot2vm.cset -- all other changes are in bug_47052_v1.cset)
2. make __go_line__ accept a matrix consisting of many lines, instead of a
single line
3. Instead of creating a new line from scratch each time, clone the first line
and change its y properties.  (This seems to make the most difference, but I
can't see why.)


Things still to do include:
- Calculate line style and line marker (__next_linestyle__ into C++); handle
colours with "hold all"
- Set xsource correctely for each line


Questions I have are:
- Is there an obvious flaw in doing this?
- Is there a better way of doing this?
- Is the an underlying reason for the slowness that should be fixed instead of
worked around?
- Once this is finished, should it also be done for primitives like surf?

(file #36326)
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Additional Item Attachment:

File name: bug_47052_v1.cset              Size:12 KB


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