Re: [Matplotlib-users] Qt4/PySide memory leak

[Christoph G. <cg...@uc...>]

On 9/24/2012 5:50 PM, Christoph Gohlke wrote:
> On 9/24/2012 3:32 PM, David Honcik wrote:
>> I've run into a large memory leak using Matplotlib with PySide and the
>> Qt4 back end.  I'm using :
>> Python 3.2
>> Numpy 1.6.2
>> Pyside 1.1.1 (qt474)
>> Matplotlib 1.2 (first the Capetown Group port to Python 3, then 1.2 RC2)
>> on Windows XP 32 bit
>> I've tried using the Python 2.7 branch of all of the above and don't see
>> the problem.  I don't see the problem with the Tk back end.  I don't see
>> the problem with the Qt4 back end and PyQt4.  Only with the above
>> mentioned versions and using the Qt4 back end with PySide.
>> The following script will reproduce the problem :
>> --------------------
>> import matplotlib
>> matplotlib.use('Qt4Agg')
>> matplotlib.rcParams['backend.qt4']='PySide'
>> import pylab
>> arrayX = []
>> arrayY = []
>> for nIndex in range(0, 100):
>> arrayX.append(nIndex)
>> arrayY.append(nIndex)
>> Figure = matplotlib.pyplot.figure(1)
>> Axes = Figure.add_axes([ 0.05, 0.05, 0.95, 0.95])
>> Axes.plot(arrayX,
>> arrayY,
>> color      = "blue",
>> marker     = "o",
>>             markersize = 5.0)
>> Axes.set_xlim(arrayX[0], arrayX[len(arrayX) - 1])
>> Axes.set_ylim(arrayY[0], arrayY[len(arrayY) - 1])
>> matplotlib.pyplot.show()
>> --------------------
>> I run the above, grab the lower right sizing handle on the plot window
>> and start resizing the window.  Watching the python process in task
>> manager, each resize leaks a noticeable amount of memory.  A few minutes
>> of this will get process memory up to ~2.5 GB. At that point it crashes.
>> I'm new here, am I in the right place?
>>
>
> I can reproduce this exactly, also with pyside 1.1.2 and an empty plot.
> Looks like QtGui.QImage is leaking.
>
> import matplotlib
> matplotlib.use('Qt4Agg')
> matplotlib.rcParams['backend.qt4']='PySide'
> from matplotlib import pyplot
> pyplot.plot()
> pyplot.show()
>
> --
> Christoph
>
>

As a workaround, until PySide is fixed, use the attached patch, which 
forcibly decreases the reference count of the string buffer after use.

Christoph