Re: [Matplotlib-users] memory usage (leakage?) in ipython interactive mode

[Gary R. <gr...@bi...>]

Hi Michael,

Thanks for your explanation. It turns out that it is a combination of
(1) and (3). I hadn't thought about (1) and I hadn't done enough
playing to see the python interpreter releasing blocks of memory. As
you suggested, the "solution" is to limit the iPython cache by using
the iPython -cs option.

thanks for your help,
Gary

Michael Droettboom wrote:
> There are at least three possible causes of what you're seeing here:
> 
> 1) ipython stores references to all results in the console.  (ipython 
> maintains a history of results so they can easily be accessed later).  I 
> don't recall the details, but it may be possible to turn this feature 
> off or limit the number of objects stored.
> 
> 2) matplotlib stores references to all figures until they are explicitly 
> closed with pyplot.close(fignum)
> 
> 3) Python uses pools of memory, and is often imposes a significant delay 
> returning memory to the operating system.  It is actually very hard to 
> determine from the outside whether something is leaking or just pooling 
> without compiling a special build of Python with memory pooling turned off.
> 
> In general, interactive use is somewhat at odds with creating many large 
> plots in a single session, since all of the nice interactive features 
> (history etc.) do not know automagically when the user is done with 
> certain objects.
> 
> I am not aware of any memory leaks in current versions of matplotlib 
> with *noninteractive* use, other than small leaks caused by bugs in 
> older versions of some of the GUI toolkits (notably gtk+).  If you find 
> a script that produces a leak reproducibly, please share so we can track 
> down the cause.
> 
> Gary Ruben wrote:
>> Doing plot(rand(1000000)) or matshow(rand(1000,1000)) for example eats 
>> a big chunk of memory (tried with TkAgg and WxAgg in Windows (mpl 
>> v0.98.5.2) and Linux (mpl v0.98.3)), most of which is not returned 
>> when the window is closed. The same goes if you create an array, plot 
>> it, and explicitly del it after closing the window.
> Can you elaborate on these steps?  It's possible that the del has little 
> effect, since del only deletes a single reference to the object, not all 
> references which may be keeping it alive (such as the figure, which 
> matplotlib itself keeps a reference to).  In general, you need to 
> explicitly call pyplot.close(fignum) to delete a figure.
> 
> Cheers,
> Mike
>