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Fri Jun 20 17:04:00 CEST 2008 · http://mail.python.org/pipermail/python-dev/2008-June/080551.html

On Fri, Jun 20, 2008 at 10:25 AM, Antoine Pitrou <solipsis at pitrou.net>
wrote:

>
> Kevin Jacobs <jacobs <at> bioinformed.com> <bioinformed <at> gmail.com>
> writes:
> >
> > +1 on a C API for enabling and disabling GC.  I have several instances
> where
> I create a large number of objects non-cyclic objects where I see huge GC
> overhead (30+ seconds with gc enabled, 0.15 seconds when disabled).
>
> Could you try to post a stripped-down, self-contained example of such
> behaviour?

$ python -m timeit 'zip(*[range(1000000)]*5)'
10 loops, best of 3: 496 msec per loop

$ python -m timeit -s 'import gc; gc.enable()' 'zip(*[range(1000000)]*5)'
10 loops, best of 3: 2.93 sec per loop

Note that timeit cheats and disables GC by default.

Attached is a less stripped down script to demonstrate the super-linear
behavior for somewhat naively coded transpose operators.  The output is
listed below:

FUNCTION        ROWS         COLUMNS     GC ENABLED    GC DISABLED
--------------  -----------  ----------  ------------  ------------
transpose_comp            5           0        0.0000        0.0000
transpose_comp            5      250000        0.5535        0.3537
transpose_comp            5      500000        1.4359        0.6868
transpose_comp            5      750000        2.7148        1.0760
transpose_comp            5     1000000        3.8070        1.3936
transpose_comp            5     1250000        5.5184        1.7617
transpose_comp            5     1500000        7.8828        2.1308
transpose_comp            5     1750000        9.3279        2.5364
transpose_comp            5     2000000       11.8248        2.7399
transpose_comp            5     2250000       14.7436        3.1585
transpose_comp            5     2500000       18.4452        3.5818
transpose_comp            5     2750000       21.4856        3.8988
transpose_comp            5     3000000       24.4110        4.3148
transpose_zip             5           0        0.0000        0.0000
transpose_zip             5      250000        0.2537        0.0658
transpose_zip             5      500000        0.8380        0.1324
transpose_zip             5      750000        1.7507        0.1989
transpose_zip             5     1000000        2.6169        0.2648
transpose_zip             5     1250000        4.0760        0.3317
transpose_zip             5     1500000        5.8852        0.4145
transpose_zip             5     1750000        7.3925        0.5161
transpose_zip             5     2000000       10.0755        0.6708
transpose_zip             5     2250000       14.2698        0.7760
transpose_zip             5     2500000       16.7291        0.9022
transpose_zip             5     2750000       20.3833        1.0179
transpose_zip             5     3000000       24.5515        1.0971

Hope this helps,
-Kevin
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[Python-Dev] C API for gc.enable() and gc.disable()