Antoine Pitrou pit...@free.fr added the comment:
Raymond, unless you object, I'd like to commit this before beta1.
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Changes by Philip Jenvey pjen...@underboss.org:
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Raymond Hettinger rhettin...@users.sourceforge.net added the comment:
Thx.
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resolution: - accepted
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Antoine Pitrou pit...@free.fr added the comment:
Modified patch committed in r86905. Thanks!
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resolution: accepted - fixed
stage: patch review - committed/rejected
status: open - closed
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Jean-Paul Calderone inva...@example.invalid added the comment:
I'll be looking at it shortly. Py3.2 is still aways from release so there is
no hurry.
I would consider reviewing and possibly apply this change, but I don't want to
invade anyone's territory.
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Antoine Pitrou pit...@free.fr added the comment:
I would consider reviewing and possibly apply this change, but I don't
want to invade anyone's territory.
I don't think there would be any invasion. I think the patch is simple enough,
and seems to provide a nice benefit.
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Raymond Hettinger rhettin...@users.sourceforge.net added the comment:
Please leave this for me.
Thank you.
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Changes by Daniel Stutzbach dan...@stutzbachenterprises.com:
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Andrew Bennetts s...@users.sourceforge.net added the comment:
On 2010-05-17 rhettinger wrote:
Will look at this when I get back to the U.S.
Ping! This patch (set-difference-speedup-2.diff) has been sitting around for a
fair few weeks now. It's a small patch, so it should be relatively easy
Changes by Florent Xicluna florent.xicl...@gmail.com:
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Alexander Belopolsky belopol...@users.sourceforge.net added the comment:
Andrew,
This issue is somewhat similar to issue8425. I may be reading too much into
the priority field, but it looks like Raymond would like to review #8425
first. You can help by commenting on how the two issues
Raymond Hettinger rhettin...@users.sourceforge.net added the comment:
I'll be looking at it shortly. Py3.2 is still aways from release so there is
no hurry.
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Andrew Bennetts s...@users.sourceforge.net added the comment:
Alexander: yes, they are complementary. My patch improves set.difference,
which always creates a new set. issue8425 on the other hand improves in-place
difference (via the -= operator or set.difference_update). Looking at the two
Raymond Hettinger rhettin...@users.sourceforge.net added the comment:
Will look at this when I get back to the U.S.
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Andrew Bennetts s...@users.sourceforge.net added the comment:
Antoine: Thanks for the updated benchmark results! I should have done that
myself earlier.
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Antoine Pitrou pit...@free.fr added the comment:
The current patch gives much smaller benefits than the originally posted
benchmarks, although they are still substantial:
$ ./python -m timeit -s a = set(range(10)); sd = a.difference; b =
set(range(1000)) sd(b)
- before: 5.56 msec per loop
Changes by Andrew Bennetts s...@users.sourceforge.net:
Added file: http://bugs.python.org/file17306/set-mem.py
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Antoine Pitrou pit...@free.fr added the comment:
1. In constrained memory environments, creating a temporary internal
copy of a large set may cause the difference operation to fail that
would otherwise succeed.
It's a space/time tradeoff. There's nothing wrong about that.
(do note that hash
Andrew Bennetts s...@users.sourceforge.net added the comment:
Regarding memory, good question... but this patch turns out to be an
improvement there too.
This optimisation only applies when len(x) len(y) * 4. So the minimum size
of the result is a set with 3/4 of the elems of x (and
New submission from Andrew Bennetts s...@users.sourceforge.net:
set.difference(s), when s is also a set, basically does::
res = set()
for elem in self:
if elem not in other:
res.add(elem)
This is wasteful when len(self) is much greater than len(other):
$ python -m
Andrew Bennetts s...@users.sourceforge.net added the comment:
Oops, obvious bug in this patch. set('abc') - set('bcd') != set('bcd') -
set('abc'). I'll see if I can make a more sensible improvement.
See also http://bugs.python.org/issue8425. Thanks dickinsm on #python-dev.
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Changes by Mark Dickinson dicki...@gmail.com:
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nosy: +rhettinger
versions: +Python 3.2
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Andrew Bennetts s...@users.sourceforge.net added the comment:
Ok, this time test_set* passes :)
Currently if you have large set and small set the code will do len(large)
lookups in the small set. When large is than small, it is cheaper to copy
large and do len(small) lookups in large. On
Changes by Alexander Belopolsky belopol...@users.sourceforge.net:
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Alexander Belopolsky belopol...@users.sourceforge.net added the comment:
I have two problems with this proposal:
1. In constrained memory environments, creating a temporary internal copy of a
large set may cause the difference operation to fail that would otherwise
succeed.
2. The break-even
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