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MRO computation could be faster #76560

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pitrou opened this issue Dec 19, 2017 · 5 comments
Closed

MRO computation could be faster #76560

pitrou opened this issue Dec 19, 2017 · 5 comments
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3.7 (EOL) end of life interpreter-core (Objects, Python, Grammar, and Parser dirs) performance Performance or resource usage

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@pitrou
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pitrou commented Dec 19, 2017

BPO 32379
Nosy @pitrou, @vstinner, @methane, @serhiy-storchaka
PRs
  • bpo-32379: Faster MRO computation for single inheritance #4932
    		•

    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 2017-12-20.14:58:51.444>
created_at = <Date 2017-12-19.19:54:59.746>
labels = ['interpreter-core', '3.7', 'performance']
title = 'MRO computation could be faster'
updated_at = <Date 2017-12-20.14:58:51.443>
user = 'https://github.com/pitrou'

    bugs.python.org fields:

    activity = <Date 2017-12-20.14:58:51.443>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2017-12-20.14:58:51.444>
closer = 'pitrou'
components = ['Interpreter Core']
creation = <Date 2017-12-19.19:54:59.746>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 32379
keywords = ['patch']
message_count = 5.0
messages = ['308674', '308675', '308733', '308734', '308737']
nosy_count = 4.0
nosy_names = ['pitrou', 'vstinner', 'methane', 'serhiy.storchaka']
pr_nums = ['4932']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue32379'
versions = ['Python 3.7']
    @pitrou
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    pitrou commented Dec 19, 2017

    MRO computation involves a complicated merge calculation over several lists. But, for the simple (common) case where a class has a single base, the computation could be much simpler: take the base's MRO and prepend the derived class.

    @pitrou pitrou added 3.7 (EOL) end of life interpreter-core (Objects, Python, Grammar, and Parser dirs) performance Performance or resource usage labels Dec 19, 2017
    @pitrou
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    pitrou commented Dec 19, 2017

    Benchmarks:

    • before:
    $ ./env-orig/bin/pyperf timeit "class Test: pass"
.....................
Mean +- std dev: 9.51 us +- 0.17 us
    • after:
    $ ./env/bin/pyperf timeit "class Test: pass"
.....................
Mean +- std dev: 8.89 us +- 0.09 us

    @serhiy-storchaka
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    LGTM in general. But mro() returns a list.

    "class Test: pass" is a trivial case. What are results if the class has a parent?

    @pitrou
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    pitrou commented Dec 20, 2017

    Benchmarks with a parent:

    • Before:
    $ ./env-orig/bin/pyperf timeit -s "from unittest import TestCase" "class Test(TestCase): pass"
.....................
Mean +- std dev: 10.4 us +- 0.1 us
    • After:
    $ ./env/bin/pyperf timeit -s "from unittest import TestCase" "class Test(TestCase): pass"
.....................
Mean +- std dev: 9.89 us +- 0.12 us

    @pitrou
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    pitrou commented Dec 20, 2017

    New changeset 1f1a34c by Antoine Pitrou in branch 'master':
    bpo-32379: Faster MRO computation for single inheritance (bpo-4932)
    1f1a34c

    @pitrou pitrou closed this as completed Dec 20, 2017
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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