I figured the reference to the object through the local scope would also be tracked by the GC somehow, since the entire stack frame can be regarded as a separate object itself, but apparently not.
On Mon, Sep 15, 2014 at 1:06 PM, Mads Ipsen <mads.ip...@gmail.com> wrote: > Thanks to everybody for taking time to answer! > > Best regards, > > Mads > > On 15/09/14 12:11, Sebastian Berg wrote: > > On Mo, 2014-09-15 at 12:05 +0200, Eelco Hoogendoorn wrote: > >> > >> > >> > >> On Mon, Sep 15, 2014 at 11:55 AM, Sebastian Berg > >> <sebast...@sipsolutions.net> wrote: > >> On Mo, 2014-09-15 at 10:16 +0200, Mads Ipsen wrote: > >> > Hi, > >> > > >> > I am trying to inspect the reference count of numpy arrays > >> generated by > >> > my application. > >> > > >> > Initially, I thought I could inspect the tracked objects > >> using > >> > gc.get_objects(), but, with respect to numpy objects, the > >> returned > >> > container is empty. For example: > >> > > >> > import numpy > >> > import gc > >> > > >> > data = numpy.ones(1024).reshape((32,32)) > >> > > >> > objs = [o for o in gc.get_objects() if isinstance(o, > >> numpy.ndarray)] > >> > > >> > print objs # Prints empty list > >> > print gc.is_tracked(data) # Print False > >> > > >> > Why is this? Also, is there some other technique I can use > >> to inspect > >> > all numpy generated objects? > >> > > >> > >> Two reasons. First of all, unless your array is an object > >> arrays (or a > >> structured one with objects in it), there are no objects to > >> track. The > >> array is a single python object without any referenced objects > >> (except > >> possibly its `arr.base`). > >> > >> Second of all -- and this is an issue -- numpy doesn't > >> actually > >> implement the traverse slot, so it won't even work for object > >> arrays > >> (numpy object arrays do not support circular garbage > >> collection at this > >> time, please feel free to implement it ;)). > >> > >> - Sebastian > >> > >> > >> > >> > >> > >> > >> Does this answer why the ndarray object itself isn't tracked though? I > >> must say I find this puzzling; the only thing I can think of is that > >> the python compiler notices that data isn't used anymore after its > >> creation, and deletes it right after its creation as an optimization, > >> but that conflicts with my own experience of the GC. > >> > >> > > > > Not sure if it does, but my quick try and error says: > > In [15]: class T(tuple): > > ....: pass > > ....: > > > > In [16]: t = T() > > > > In [17]: objs = [o for o in gc.get_objects() if isinstance(o, T)] > > > > In [18]: objs > > Out[18]: [()] > > > > In [19]: a = 123. > > > > In [20]: objs = [o for o in gc.get_objects() if isinstance(o, float)] > > > > In [21]: objs > > Out[21]: [] > > > > So I guess nothing is tracked, unless it contains things, and numpy > > arrays don't say they can contain things (i.e. no traverse). > > > > - Sebastian > > > > > > > >> _______________________________________________ > >> NumPy-Discussion mailing list > >> NumPy-Discussion@scipy.org > >> http://mail.scipy.org/mailman/listinfo/numpy-discussion > > > > > > > > _______________________________________________ > > NumPy-Discussion mailing list > > NumPy-Discussion@scipy.org > > http://mail.scipy.org/mailman/listinfo/numpy-discussion > > > > -- > +---------------------------------------------------------+ > | Mads Ipsen | > +----------------------+----------------------------------+ > | Gåsebæksvej 7, 4. tv | phone: +45-29716388 | > | DK-2500 Valby | email: mads.ip...@gmail.com | > | Denmark | map : www.tinyurl.com/ns52fpa | > +----------------------+----------------------------------+ > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion >
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