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gh-144650: support Vectorcall for _decimal.Decimal's - #158207

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skirpichev:decimal-ac/144650
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gh-144650: support Vectorcall for _decimal.Decimal's#158207
skirpichev wants to merge 11 commits into
python:mainfrom
skirpichev:decimal-ac/144650

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@skirpichev

@skirpichev skirpichev commented Sep 26, 2026 •
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This shows almost no effect on "official" pyperformance benchmarks (see python/pyperformance#473):

Benchmarks with tag 'decimal':
==============================

decimal_pi: Mean +- std dev: [ref] 1.97 sec +- 0.01 sec -> [patch] 1.95 sec +- 0.02 sec: 1.01x faster

Benchmark hidden because not significant (1): decimal_factorial

Geometric mean: 1.01x faster

But on micro-benchmarks:

Benchmark ref patch
Decimal(0) 620 ns 537 ns: 1.15x faster
Decimal(123) 621 ns 540 ns: 1.15x faster
Decimal('123') 788 ns 677 ns: 1.16x faster
Geometric mean (ref) 1.16x faster

(Default ./configure options, gcc 14.2)

Details 
# bench.py
import pyperf
from decimal import Decimal

runner = pyperf.Runner()
for x in [0, 123, '123']:
    h = f"Decimal({x!r})"
    runner.bench_func(h, Decimal, x)

@skirpichev skirpichev changed the title Support Vectorcall for _decimal.Decimal's gh-144650: support Vectorcall for _decimal.Decimal's Sep 26, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Sep 26, 2026
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@cmaloney

cmaloney commented Sep 26, 2026

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#157968 may help with the build failures (changes how the assert works which should make it better across module boundaries)

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skirpichev commented Sep 26, 2026

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Thanks. The Decimal is only possible candidate being a heap type in the stdlib. That was worked before in skirpichev#18

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skirpichev marked this pull request as draft September 26, 2026 03:02
@skirpichev skirpichev self-assigned this Sep 26, 2026
@cmaloney

cmaloney commented Sep 26, 2026

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👍 hopefully will get more of these landed soon :). str and list still need some special work for stable performance over the change which I'm still root causing (likely compiler inlining vs. existing hand inlining). If there are ways I can help enable / particular edge cases you find let me know. Otherwise planning to make PRs as I have time + performance results for existing cases across the codebase (int, float, str, list, bytes, bytearray, bool, filter, set, frozenset are on my radar).

cmaloney and others added 3 commits September 26, 2026 06:31
@cmaloney @skirpichev
pythongh-150097: Move _testclinic to multi-phase init
6c3d922 
Convert the static types to heap types. Move empty init vectorcall to
share with existing no-arg __init__ case. Add support for no-argument
vectorcall so the no-arg __init__ cases actually work (rather than
adding an arg). Produce the same error string as the PyArg helpers do.

The vectorcall types no longer have a C address for the generated
`Py_Is` so instead compare the slot function instead. This drops the
requirement that a class using vectorcall declare a type object.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

(cherry-picked from python#157968)
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run AC
6df90e5
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+1
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skirpichev marked this pull request as ready for review September 26, 2026 03:41
@skirpichev skirpichev removed their assignment Oct 2, 2026
@bedevere-app bedevere-app Bot added the type-feature A feature request or enhancement label Oct 6, 2026
@skirpichev

skirpichev commented Oct 8, 2026 •
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CC @vstinner, does it make sense for you?

Edit: N.B., this depends on #157968.

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Merge branch 'master' into decimal-ac/144650
40253f5 
# Conflicts:
#	Modules/clinic/_testclinic.c.h
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@skirpichev skirpichev closed this Oct 17, 2026
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skirpichev deleted the decimal-ac/144650 branch October 17, 2026 03:07
@vstinner

vstinner commented Oct 18, 2026

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Did you close it because you consider that it's not worth it?

@skirpichev

skirpichev commented Oct 18, 2026

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I think it still worth it, assuming micro-benchmarks. It's for free, anyway.

But it's on top of #157968. If you are ok, I'll reopen this one that pr (or some its alternative) will be merged.

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