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Optimize UTF-8 decoder with error handlers #69488

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vstinner opened this issue Oct 2, 2015 · 6 comments
Closed

Optimize UTF-8 decoder with error handlers #69488

vstinner opened this issue Oct 2, 2015 · 6 comments
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expert-unicode performance Performance or resource usage

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@vstinner
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vstinner commented Oct 2, 2015

BPO 25301
Nosy @vstinner, @ezio-melotti
Files
  • utf8_decoder.patch
  • bench.py
  • Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
    closed_at = <Date 2015-10-05.11:44:37.727>
    created_at = <Date 2015-10-02.14:44:42.656>
    labels = ['expert-unicode', 'performance']
    title = 'Optimize UTF-8 decoder with error handlers'
    updated_at = <Date 2015-10-05.11:49:36.115>
    user = 'https://github.com/vstinner'

    bugs.python.org fields:

    activity = <Date 2015-10-05.11:49:36.115>
    actor = 'python-dev'
    assignee = 'none'
    closed = True
    closed_date = <Date 2015-10-05.11:44:37.727>
    closer = 'vstinner'
    components = ['Unicode']
    creation = <Date 2015-10-02.14:44:42.656>
    creator = 'vstinner'
    dependencies = []
    files = ['40663', '40671']
    hgrepos = []
    issue_num = 25301
    keywords = ['patch']
    message_count = 6.0
    messages = ['252117', '252181', '252264', '252319', '252320', '252321']
    nosy_count = 3.0
    nosy_names = ['vstinner', 'ezio.melotti', 'python-dev']
    pr_nums = []
    priority = 'normal'
    resolution = 'fixed'
    stage = None
    status = 'closed'
    superseder = None
    type = 'performance'
    url = 'https://bugs.python.org/issue25301'
    versions = ['Python 3.6']

    @vstinner
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    vstinner commented Oct 2, 2015

    The issue bpo-24870 optimized the ASCII decoder with error handlers:

    New changeset 3c430259873e by Victor Stinner in branch 'default':
    Issue bpo-24870: Optimize the ASCII decoder for error handlers: surrogateescape,
    https://hg.python.org/cpython/rev/3c430259873e

    We should also optimize the UTF-8 decoder with error handlers.

    I will work on a patch next days.

    @vstinner vstinner added expert-unicode performance Performance or resource usage labels Oct 2, 2015
    @vstinner
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    vstinner commented Oct 3, 2015

    Here is a first patch. It is written to keep best performances for valid UTF-8 encoded string, but speedup strings with a few undecodable bytes.

    @vstinner
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    vstinner commented Oct 4, 2015

    Results of the microbenchmark on the UTF-8 decoder.

    As expected, performances on valid UTF-8 is unchanged, which was an important goal for me.

    Decoding with error handlers optimized by the patch are *much* faster.

    backslashreplace is still slow, because I didn't optimize it.

    Common platform:
    Python unicode implementation: PEP-393
    Timer: time.perf_counter
    Platform: Linux-4.1.5-200.fc22.x86_64-x86_64-with-fedora-22-Twenty_Two
    CPU model: Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz
    Timer info: namespace(adjustable=False, implementation='clock_gettime(CLOCK_MONOTONIC)', monotonic=True, resolution=1e-09)
    Bits: int=32, long=64, long long=64, size_t=64, void*=64
    CFLAGS: -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes
    Timer precision: 55 ns

    Platform of campaign before:
    SCM: hg revision=f51921883f50 tag=tip branch=default date="2015-10-04 01:19 -0400"
    Python version: 3.6.0a0 (default:f51921883f50, Oct 4 2015, 10:19:37) [GCC 5.1.1 20150618 (Red Hat 5.1.1-4)]
    Date: 2015-10-04 10:19:44

    Platform of campaign after:
    SCM: hg revision=f51921883f50+ tag=tip branch=default date="2015-10-04 01:19 -0400"
    Python version: 3.6.0a0 (default:f51921883f50+, Oct 4 2015, 10:14:05) [GCC 5.1.1 20150618 (Red Hat 5.1.1-4)]
    Date: 2015-10-04 10:18:55

    ---------------------+-------------+--------
    valid UTF-8 (strict) | before | after
    ---------------------+-------------+--------
    100 x 10**1 bytes | 297 ns () | 297 ns
    100 x 10**3 bytes | 7.4 us (
    ) | 7.44 us
    100 x 10**2 bytes | 929 ns () | 924 ns
    100 x 10**4 bytes | 80.4 us (
    ) | 80.4 us
    ---------------------+-------------+--------
    Total | 89.1 us (*) | 89 us
    ---------------------+-------------+--------

    ------------------+-------------+---------------
    ignore | before | after
    ------------------+-------------+---------------
    100 x 10**1 bytes | 6.68 us () | 743 ns (-89%)
    100 x 10**3 bytes | 561 us (
    ) | 42.6 us (-92%)
    100 x 10**2 bytes | 56.8 us () | 4.55 us (-92%)
    100 x 10**4 bytes | 6.02 ms (
    ) | 425 us (-93%)
    ------------------+-------------+---------------
    Total | 6.65 ms (*) | 473 us (-93%)
    ------------------+-------------+---------------

    ------------------+-------------+---------------
    replace | before | after
    ------------------+-------------+---------------
    100 x 10**1 bytes | 7.61 us () | 890 ns (-88%)
    100 x 10**3 bytes | 639 us (
    ) | 50.3 us (-92%)
    100 x 10**2 bytes | 64.8 us () | 5.37 us (-92%)
    100 x 10**4 bytes | 7.09 ms (
    ) | 505 us (-93%)
    ------------------+-------------+---------------
    Total | 7.81 ms (*) | 561 us (-93%)
    ------------------+-------------+---------------

    ------------------+-------------+---------------
    surrogateescape | before | after
    ------------------+-------------+---------------
    100 x 10**1 bytes | 7.96 us () | 855 ns (-89%)
    100 x 10**3 bytes | 674 us (
    ) | 50.2 us (-93%)
    100 x 10**2 bytes | 68.8 us () | 5.35 us (-92%)
    100 x 10**4 bytes | 7.38 ms (
    ) | 504 us (-93%)
    ------------------+-------------+---------------
    Total | 8.13 ms (*) | 560 us (-93%)
    ------------------+-------------+---------------

    ------------------+-------------+--------
    backslashreplace | before | after
    ------------------+-------------+--------
    100 x 10**1 bytes | 7.66 us () | 7.89 us
    100 x 10**3 bytes | 633 us (
    ) | 633 us
    100 x 10**2 bytes | 64.1 us () | 64.6 us
    100 x 10**4 bytes | 6.9 ms (
    ) | 6.93 ms
    ------------------+-------------+--------
    Total | 7.61 ms (*) | 7.64 ms
    ------------------+-------------+--------

    ---------------------+-------------+---------------
    Summary | before | after
    ---------------------+-------------+---------------
    valid UTF-8 (strict) | 89.1 us () | 89 us
    ignore | 6.65 ms (
    ) | 473 us (-93%)
    replace | 7.81 ms () | 561 us (-93%)
    surrogateescape | 8.13 ms (
    ) | 560 us (-93%)
    backslashreplace | 7.61 ms () | 7.64 ms
    ---------------------+-------------+---------------
    Total | 30.3 ms (
    ) | 9.32 ms (-69%)
    ---------------------+-------------+---------------

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    python-dev mannequin commented Oct 5, 2015

    New changeset 3152e4038d97 by Victor Stinner in branch 'default':
    Issue bpo-25301: The UTF-8 decoder is now up to 15 times as fast for error
    https://hg.python.org/cpython/rev/3152e4038d97

    @vstinner
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    vstinner commented Oct 5, 2015

    I pushed my optimization. I close the issue.

    @vstinner vstinner closed this as completed Oct 5, 2015
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    python-dev mannequin commented Oct 5, 2015

    New changeset 5b9ffea7e7c3 by Victor Stinner in branch 'default':
    Issue bpo-25301: Fix compatibility with ISO C90
    https://hg.python.org/cpython/rev/5b9ffea7e7c3

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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