[Bug]: Memory leak with colorbar.make_axes · Issue #22085 · matplotlib/matplotlib · GitHub

Bug summary

When using matplotlib.colorbar.make_axes function, plt.close() does not clear the new colorbar axes from memory. Tested for the Qt5 backend only. Maybe related to #22002, at least in the sense that I see no leak for Qt5 when no colorbar axes are added.

Code for reproduction

%pylab qt5
from matplotlib import colorbar
import psutil
import gc

p = psutil.Process()
for i in range(5):
    fig, ax = plt.subplots(1,1)
    ax.imshow(random.normal(size=(100,100)))
    cax = colorbar.make_axes(ax)
    plt.savefig("test.png")
    plt.pause(0.1)
    plt.close(fig)
    del fig
    del ax
    del cax
    gc.collect()
    print(p.memory_full_info().uss/1e6)

Actual outcome

250.744832
255.209472
259.514368
264.13056
268.099584

Expected outcome

Constant memory usage, as is when the line
cax = colorbar.make_axes(ax)
is commented out.

Additional information

No response

Operating system

Windows

Matplotlib Version

3.4.2

Matplotlib Backend

Qt5Agg (PyQt)

Python version

3.7.6

Jupyter version

No response

Installation

from source (.tar.gz)

Oh, also just found #22040, probably mine is a duplicate. The difference is that I do not yet know, how to workaround the problem in my example.

Perhaps also test the latest matplotlib. There were substantial changes to colorbar for 3.5. FWIW, I don;t know what make_axes is supposed to do in your code.

OK, I can confirm this when make_axes is used. When make_axes_gridspec is used, there is no memory leak.

If I insert

...
    del ax 
    del cax._colorbar_info
    del cax
...

then the memory leak goes away.

This is defined in make_axes:

matplotlib/lib/matplotlib/colorbar.py

Lines 1463 to 1471 in 0c1aa86

    
           cax._colorbar_info = dict( 
        
               location=location, 
        
               parents=parents, 
        
               shrink=shrink, 
        
               anchor=anchor, 
        
               panchor=panchor, 
        
               fraction=fraction, 
        
               aspect=aspect0, 
        
               pad=pad)

and used by constrained_layout. I am not clear why adding a dictionary to an object would leave the dictionary orphaned when the parent is deleted?

Yes, I found that grid spec helps, too, thank you!

The culprit is parents = np.atleast_1d(parents).ravel(). If I get rid of this, no memory leak. However, this is needed, and I am not sure why it leaks.

@jklymak Thank you very much!

[Bug]: Memory leak with colorbar.make_axes · Issue #22085 · matplotlib/matplotlib · GitHub

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[Bug]: Memory leak with colorbar.make_axes #22085

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	cax._colorbar_info = dict(
	location=location,
	parents=parents,
	shrink=shrink,
	anchor=anchor,
	panchor=panchor,
	fraction=fraction,
	aspect=aspect0,
	pad=pad)

[Bug]: Memory leak with colorbar.make_axes · Issue #22085 · matplotlib/matplotlib · GitHub

Repository navigation

[Bug]: Memory leak with colorbar.make_axes #22085

Description

Bug summary

Code for reproduction

Actual outcome

Expected outcome

Additional information

Operating system

Matplotlib Version

Matplotlib Backend

Python version

Jupyter version

Installation

Activity

vdrhtc commented on Jan 2, 2022

jklymak commented on Jan 2, 2022

jklymak commented on Jan 3, 2022

jklymak commented on Jan 3, 2022

vdrhtc commented on Jan 3, 2022

jklymak commented on Jan 3, 2022

vdrhtc commented on Jan 3, 2022

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