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gh-91404: Improve re performance #91495

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Merged
brandtbucher merged 10 commits into from
Apr 15, 2022
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gh-91404: Improve re performance #91495

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89e4e5e
Try out computed gotos in the regex engine
brandtbucher Apr 12, 2022
bc378d8
Reduce indirection
brandtbucher Apr 12, 2022
fa98784
More of that
brandtbucher Apr 12, 2022
48a7f1c
Rearrange some stuff
brandtbucher Apr 12, 2022
6f8a9a0
Whitespace
brandtbucher Apr 12, 2022
03d3194
Generate sre_targets.h
brandtbucher Apr 12, 2022
24fa5a1
Catch up with main
brandtbucher Apr 13, 2022
0d30328
blurb add
brandtbucher Apr 13, 2022
fdcde9f
fixup
brandtbucher Apr 13, 2022
d38743f
What's New
brandtbucher Apr 14, 2022
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6 changes: 6 additions & 0 deletions Doc/whatsnew/3.11.rst
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Expand Up @@ -512,6 +512,12 @@ Optimizations
becomes 272 bytes from 352 bytes on 64bit platform.
(Contributed by Inada Naoki in :issue:`46845`.)

* :mod:`re`'s regular expression matching engine has been partially refactored,
and now uses computed gotos (or "threaded code") on supported platforms. As a
result, Python 3.11 executes the `pyperformance regular expression benchmarks
<https://pyperformance.readthedocs.io/benchmarks.html#regex-dna>`_ up to 10%
faster than Python 3.10.


Faster CPython
==============
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7 changes: 4 additions & 3 deletions Makefile.pre.in
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Expand Up @@ -1351,11 +1351,12 @@ regen-stdlib-module-names: build_all Programs/_testembed
$(UPDATE_FILE) $(srcdir)/Python/stdlib_module_names.h $(srcdir)/Python/stdlib_module_names.h.new

regen-sre:
# Regenerate Modules/_sre/sre_constants.h from Lib/re/_constants.py
# using Tools/scripts/generate_sre_constants.py
# Regenerate Modules/_sre/sre_constants.h and Modules/_sre/sre_targets.h
# from Lib/re/_constants.py using Tools/scripts/generate_sre_constants.py
$(PYTHON_FOR_REGEN) $(srcdir)/Tools/scripts/generate_sre_constants.py \
$(srcdir)/Lib/re/_constants.py \
$(srcdir)/Modules/_sre/sre_constants.h
$(srcdir)/Modules/_sre/sre_constants.h \
$(srcdir)/Modules/_sre/sre_targets.h

Python/compile.o Python/symtable.o Python/ast_unparse.o Python/ast.o Python/future.o: $(srcdir)/Include/internal/pycore_ast.h

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2022-04-12-19-08-13.gh-issue-91404.zjqYHo.rst
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@@ -0,0 +1,3 @@
Improve the performance of :mod:`re` matching by using computed gotos (or

@serhiy-storchaka serhiy-storchaka Apr 14, 2022

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Add that it speeds up matching by 10-20%.

@markshannon markshannon Apr 14, 2022

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Please don't. These claimed speedups are highly misleading.

The release notes for 3.9 and 3.10 have various claimed large speedups, yet 3.9 is no faster than 3.8 and 3.10 only a little bit faster.

@serhiy-storchaka serhiy-storchaka Apr 14, 2022

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The benchmark results are convincing to me.

Without this it is not clear why bother with making this change at all.

@markshannon markshannon Apr 14, 2022

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You'll only see a 10-20% speedup for these specific benchmarks, which are contrived.
Real programs, even those that spend a lot regexes will spend a much lower proportion of their time in the regex library.

Any number we give will be misleading.

@brandtbucher brandtbucher Apr 14, 2022

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This branch vs 3.10:

- regex_v8: 147 ms +- 12 ms -> 132 ms +- 11 ms: 1.11x faster
- regex_effbot: 19.1 ms +- 1.2 ms -> 17.5 ms +- 0.9 ms: 1.10x faster
- regex_dna: 1.30 sec +- 0.01 sec -> 1.24 sec +- 0.01 sec: 1.04x faster

(Those numbers are very close to what you get by combining the latest re perf regressions with the numbers from this PR.)

I'll just leave the NEWS entry as-is (very few people read it anyways). I don't have a strong opinion on what should go in What's New (but @pablogsal might).

@brandtbucher brandtbucher Apr 14, 2022

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Perhaps the wording "up to 10% faster on the pyperformance regular expression benchmarks" (or similar) might suffice.

@pablogsal pablogsal Apr 14, 2022 •
edited
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I think this should indeed go in the What's new. Could you add a small sentence in the Performance section, maybe? Specifying that the improvement is in the re engine and that it only affects re operations? If we need to remove it later is easier than the risk of forgetting to add something.

"threaded code") on supported platforms and removing expensive pointer
indirections.
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