slow rendering with backend_macosx on El Capitan #5964

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1. efiring

   added

   GUI: MacOSX

   on Feb 3, 2016
2. efiring

   added this to the 1.5.2 (Critical bug fix release)This milestone has been deleted milestone on Feb 3, 2016
3. mdboom commented on Feb 3, 2016

   

   mdboom

   on Feb 3, 2016

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   Did this also happen on Mavericks, or is it new to El Capitan? (I'm still on Mavericks, so can confirm one way or the other if you can provide a script to reproduce...)

   Is the copy-and-paste into IPython window critical, or does it also happen when running as a script?
4. efiring commented on Feb 5, 2016

   

   efiring

   on Feb 5, 2016

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   It can be demonstrated with the script below, so it does not depend on cut/paste. On a new Macbook Air, part of the plot is displayed, it pauses, and then displays the rest. On Macbook Pro Retina machines, one with Mavericks and the other with Yosemite, it doesn't display anything until the plot is complete. On the Mavericks machine (mine) I can hear the fan and see the power consumption, so evidently it is working rather than waiting. Contrary to my initial guess, I think we are just seeing slower rendering of a very large number of points with the macosx backend compared to any agg backend. I suspect this has always been the case.
   Nevertheless, I think this is one more reason for discouraging use of the macosx backend whenever an alternative is available--as it is in any Anaconda installation.

   #/usr/bin/env python
   
   import sys
   backend = sys.argv[1]
   
   import matplotlib
   matplotlib.use(backend)
   
   import matplotlib.pyplot as plt
   import numpy as np
   
   fig, axs = plt.subplots(nrows=3)
   nw = 101
   n = 300000
   x = np.arange(n, dtype=float)
   y = np.cumsum(np.random.randn(n))
   w = np.ones(nw, float) / nw
   y = np.convolve(y, w, mode='same')
   
   axs[0].plot(x, y, '.')
   axs[1].plot(x, y, '.')
   axs[2].plot(x, y, '.')
   
   plt.show()
5. tacaswell commented on Feb 5, 2016

   

   tacaswell

   on Feb 5, 2016

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   This is not super snappy with Agg

   In [12]: %timeit fig.canvas.draw()
   1 loops, best of 3: 691 ms per loop
   

   Switching to using pixel markers (',') gives

   In [14]: %timeit fig.canvas.draw()
   10 loops, best of 3: 123 ms per loop
   

   and using a line (with no markers) gives

   In [16]: %timeit fig.canvas.draw()
   10 loops, best of 3: 59.3 ms per loop
   

   Using 'o' as the marker is worse

   In [18]: %timeit fig.canvas.draw()
   1 loops, best of 3: 1.16 s per loop
   
   
6. efiring commented on Feb 5, 2016

   

   efiring

   on Feb 5, 2016

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   On my Retina with the '.' marker and macosx:

    In [15]: %timeit fig.canvas.draw()
   1 loops, best of 3: 58.9 s per loop
   

   and with qt4agg:

   In [15]: %timeit fig.canvas.draw()
   1 loops, best of 3: 614 ms per loop
   

   It will be interesting to see how qt5agg handles it when that becomes available; according to @mdboom, it will support the full resolution, while qt4agg is operating in lo-res mode.
   Presumably it will be something like the result of saving a png at high dpi:

   In [16]: %timeit fig.savefig('test.png', dpi=320)
   1 loops, best of 3: 4.26 s per loop
   
7. efiring

   modified the milestones: unassignedThis milestone has been deleted, 1.5.2 (Critical bug fix release)This milestone has been deleted on Mar 16, 2016
8. efiring commented on Mar 16, 2016

   

   efiring

   on Mar 16, 2016

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   I switched the milestone to "unassigned" because this is not something we can fix in the present macosx backend. The solution will be to use an agg-based backend, either a presently existing one, or a modification of macosx to use agg.
9. mdboom commented on Mar 21, 2016

   

   mdboom

   on Mar 21, 2016

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   Fixed by #6178
10. tacaswell

    closed this as completedon Mar 28, 2016
11. QuLogic

    modified the milestones: 2.0 (style change major release)This milestone has been deleted, unassignedThis milestone has been deleted on Mar 28, 2016