Raymond Hettinger added the comment:
Applied Sirhiy's version of the patch but may switch to the j=0 version later.
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resolution: - fixed
status: open - closed
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http://bugs.python.org/issue23269
Roundup Robot added the comment:
New changeset 0b2a3d764e63 by Raymond Hettinger in branch 'default':
Issue #23269: Tighten search_loop in set_insert_clean()
https://hg.python.org/cpython/rev/0b2a3d764e63
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nosy: +python-dev
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Python tracker
Raymond Hettinger added the comment:
May be worth to move this test outside of the loop as in the
set_lookup function.
The loop used to be this way but testing showed no benefit, so a while back I
recombined it back to a j=0 start point and the code looked much nicer. I
don't really want
Serhiy Storchaka added the comment:
I have no strong preferences. This code is used very rarely and I have no any
example which exposes performance differences. But how large the benefit of
your patch? It doesn't make the C code more clean.
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Serhiy Storchaka added the comment:
What timing results?
There is large chance that first tested entry is empty. May be worth to move
this test outside of the loop as in the set_lookup function.
i = mask; may be moved to the start of the loop.
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Added file:
Raymond Hettinger added the comment:
Reopening this with a better patch that nicely tightens the inner-loop without
an algorithmic change or any downside.
Currently, the entry computation adds a constant (i+j), masks it (mask) to
wrap on overflow, scales it to a table index ( 4), and then
Changes by Raymond Hettinger raymond.hettin...@gmail.com:
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resolution: - rejected
status: open - closed
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New submission from Raymond Hettinger:
First draft of patch to switch from a table[(i+j)mask] style of entry
calculation to an entry++ style. The entry computation simplifies from
add/shl4/and/lea to a single add16. To do this, the linear probes are limited
to the length of table rather
Changes by Serhiy Storchaka storch...@gmail.com:
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nosy: +pitrou, serhiy.storchaka
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Changes by Raymond Hettinger raymond.hettin...@gmail.com:
Added file: http://bugs.python.org/file3/measure_build_set.py
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Changes by Raymond Hettinger raymond.hettin...@gmail.com:
Added file: http://bugs.python.org/file37776/limit2.diff
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Raymond Hettinger added the comment:
Patch timings give inconsistent results. GCC-4.9 generates faster code and
CLang generates slower code :-(
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Added file: http://bugs.python.org/file37775/timings.txt
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Antoine Pitrou added the comment:
Either way the improvement doesn't look terrific, so I would suggest not to
bother with this.
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