On Thu, Jan 13, 2011 at 7:54 AM, CASOLI Jules <jules.cas...@cea.fr> wrote:
> Hello to all,
>
> This is yet another question about matplotlib not freeing memory, when
> closing a figure (using close()).
> Here is what I'm doing (tried with several backends, on MacOSX and Linux,
> with similar results):
> --------------------
> import matplotlib as mpl
> from matplotlib import pylot as plt
> import numpy as np
>
> a = np.arange(1000000)
> mpl.cbook.report_memory()
> # -> output: 54256
> plt.plot(a)
> mpl.cbook.report_memory()
> # -> output: 139968
> plt.close()
> mpl.cbook.report_memory()
> # -> output: 138748
> --------------------
>
> Shouldn't plt.close() close the figure _and_ free the memory used by it?
> What am I doing wrong ?
> I tried several other ways to free the memory, such as f = figure(); ... ;
> del f, without luck.
>
> Any help appreciated !
>
> P.S. : side question : how come the call to plot take so much memory (90MB
> for a 8MB array ?). I have read somewhere that each point is coded on three
> RGB floats, but it only means an approx. 12MB plot... (plus small overhead)
>
> Jules
>
>
>
Jules,
Which version of Matplotlib are you using and which backend? On my Linux
install of matplotlib (development branch) using GTKAgg, the memory usage
does get high during the call to show(), but returns to (near) normal
amounts after I close. An interesting observation is that if the
interactive mode is off, the memory usage returns back to just a few
kilobytes above where it was before, but if interactive mode was turned on,
the memory usage returned to being a few hundred kilobytes above where it
started.
Ben Root
P.S. - As a side note, estimating the memory size of these plots from the
given data isn't as straight-forward as multiplying by three (actually, it
would be four because of the transparency value in addition to rgb). There
are many other parts of the graph that needs to be represented (all having
rgba values) but there are also a lot of simplifications that are done to
reduce the amount of memory needed to represent these objects.
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