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gh-133968: Add fast path to PyUnicodeWriter_WriteStr() #133969

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Merged
merged 1 commit into from
May 13, 2025
Merged

gh-133968: Add fast path to PyUnicodeWriter_WriteStr() #133969

merged 1 commit into from
May 13, 2025

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@vstinner vstinner commented May 13, 2025 •
edited by bedevere-app bot
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Don't call PyObject_Str() if the input type is str.

@vstinner
pythongh-133968: Add fast path to PyUnicodeWriter_WriteStr()
8613170 
Don't call PyObject_Str() if the input type is str.
@vstinner vstinner added skip news needs backport to 3.14 bugs and security fixes labels May 13, 2025
@bedevere-app bedevere-app bot mentioned this pull request May 13, 2025
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@vstinner vstinner mentioned this pull request May 13, 2025
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Microbenchmark:

Mean +- std dev: [ref] 70.5 ns +- 1.1 ns -> [change] 58.3 ns +- 3.8 ns: 1.21x faster

from _testcapi import PyUnicodeWriter
import pyperf

range_100 = range(100)

def bench_write_str():
    writer = PyUnicodeWriter(0)
    for _ in range_100:
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")
        writer.write_str("true")

runner = pyperf.Runner()
runner.bench_func('write_str', bench_write_str, inner_loops=1_000)

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JSON benchmark: #133832 (comment)

Benchmark ref change
encode 100 booleans 9.52 us 7.18 us: 1.33x faster
encode 100 integers 13.9 us 11.6 us: 1.20x faster
encode 100 floats 25.1 us 20.6 us: 1.22x faster
encode 100 "ascii" strings 17.3 us 13.2 us: 1.31x faster
encode ascii string len=100 913 ns 902 ns: 1.01x faster
encode escaped string len=128 1.11 us 1.10 us: 1.01x faster
encode Unicode string len=100 1.09 us 1.07 us: 1.02x faster
encode 1000 booleans 59.6 us 38.9 us: 1.53x faster
encode 1000 integers 104 us 82.7 us: 1.26x faster
encode 1000 floats 210 us 166 us: 1.27x faster
encode 1000 "ascii" strings 132 us 93.2 us: 1.42x faster
encode ascii string len=1000 3.48 us 3.49 us: 1.00x slower
encode escaped string len=896 4.12 us 4.11 us: 1.00x faster
encode Unicode string len=1000 4.90 us 4.91 us: 1.00x slower
encode 10000 booleans 553 us 343 us: 1.61x faster
encode 10000 integers 1.00 ms 805 us: 1.25x faster
encode 10000 floats 2.07 ms 1.62 ms: 1.28x faster
encode 10000 "ascii" strings 1.27 ms 868 us: 1.46x faster
encode ascii string len=10000 28.4 us 28.5 us: 1.00x slower
encode escaped string len=9984 38.5 us 38.6 us: 1.00x slower
encode Unicode string len=10000 42.3 us 42.4 us: 1.00x slower
Geometric mean (ref) 1.18x faster

Encoding booleans is now up to 1.61x faster which is quite appealing!

@vstinner vstinner merged commit fe9f6e8 into python:main May 13, 2025
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@vstinner vstinner deleted the write_str branch May 13, 2025 13:31
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Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request May 13, 2025
@vstinner @miss-islington
pythongh-133968: Add fast path to PyUnicodeWriter_WriteStr() (pythonG…
616ee64 
…H-133969)

Don't call PyObject_Str() if the input type is str.
(cherry picked from commit fe9f6e8)

Co-authored-by: Victor Stinner <vstinner@python.org>
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bedevere-app bot commented May 13, 2025

GH-133971 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label May 13, 2025
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When I wrote PyUnicodeWriter_WriteStr(), I skipped this fast path since PyObject_Str() already has a fast path. But it seems like adding one in PyUnicodeWriter_WriteStr() makes a big difference on microbenchmarks!

vstinner added a commit that referenced this pull request May 13, 2025
@miss-islington @vstinner
[3.14] gh-133968: Add fast path to PyUnicodeWriter_WriteStr() (GH-133969
5632e93 
) (#133971)

gh-133968: Add fast path to PyUnicodeWriter_WriteStr() (GH-133969)

Don't call PyObject_Str() if the input type is str.
(cherry picked from commit fe9f6e8)

Co-authored-by: Victor Stinner <vstinner@python.org>
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