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timeit: use powers of 2 in autorange(), instead of powers of 10 #72655

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vstinner opened this issue Oct 18, 2016 · 8 comments
Closed

timeit: use powers of 2 in autorange(), instead of powers of 10 #72655

vstinner opened this issue Oct 18, 2016 · 8 comments
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3.7 (EOL) end of life performance Performance or resource usage stdlib Python modules in the Lib dir

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@vstinner
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BPO 28469
Nosy @vstinner, @serhiy-storchaka
PRs
  • [Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
    		•
    Files
  • timeit_autorange_pow2.patch
  • timeit_autorange_numbers.patch
    		•

    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 2016-10-23.12:19:09.850>
created_at = <Date 2016-10-18.16:13:11.315>
labels = ['3.7', 'library', 'performance']
title = 'timeit: use powers of 2 in autorange(), instead of powers of 10'
updated_at = <Date 2017-03-31.16:36:15.077>
user = 'https://github.com/vstinner'

    bugs.python.org fields:

    activity = <Date 2017-03-31.16:36:15.077>
actor = 'dstufft'
assignee = 'none'
closed = True
closed_date = <Date 2016-10-23.12:19:09.850>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2016-10-18.16:13:11.315>
creator = 'vstinner'
dependencies = []
files = ['45134', '45186']
hgrepos = []
issue_num = 28469
keywords = ['patch']
message_count = 8.0
messages = ['278899', '278905', '278906', '278915', '278916', '279187', '279245', '279254']
nosy_count = 3.0
nosy_names = ['vstinner', 'python-dev', 'serhiy.storchaka']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue28469'
versions = ['Python 3.7']
    @vstinner
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    In the issue bpo-28240, I changed the default repeat from 3 to 5 in timeit. Serhiy wrote (msg277157): "For now default timeit run takes from 0.8 to 8 sec. Adding yet 5 sec makes a user more angry."

    I propose to use powers to 2, instead of powers of 10, in timeit autorange to reduce the total duration of the microbenchmark.

    • Without the patch, the worst case: 4.0 * 6 = 24 seconds.

    • With the patch, the worst case is: 0.4 * 6 = 2.4 seconds

    • 6: autorange (1 iteration) + 5 repeatition

    • autorange uses a minimum of 200 ms, so the worst case is 200 ms * 10 before, or 200 ms * 2 after

    @vstinner vstinner added 3.7 (EOL) end of life performance Performance or resource usage labels Oct 18, 2016
    @serhiy-storchaka
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    "131072 loops" in a report looks not human friendly. I would prefer using a sequence of round numbers: 1, 2, 5, 10, 20, 50, 100, ...

    @vstinner
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    "131072 loops" in a report looks not human friendly.

    In my perf module, I use 2^n syntax for numbers larger than 1024. Syntax accepted in command line arguments.

    @serhiy-storchaka
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    The perf module doesn't report the number of loops by default.

    @vstinner
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    The perf module doesn't report the number of loops by default.

    Right, it's hidden by default. I consider that it's not an useful information for end users.

    If you want more details (see the number of inner and outer loops), use --verbose ("python3 -m perf timeit -v ...") or the stats commands ("python3 -m perf stats file.json").

    @serhiy-storchaka
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    Following patch takes numbers from the sequence 1, 2, 5, 10, 20, 50, ... It also updates the documentation and tests.

    @serhiy-storchaka serhiy-storchaka added the stdlib Python modules in the Lib dir label Oct 22, 2016
    @vstinner
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    timeit_autorange_numbers.patch: LGTM.

    @python-dev
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    Mannequin

    python-dev mannequin commented Oct 23, 2016

    New changeset 8e6cc952adc6 by Serhiy Storchaka in branch 'default':
    Issue bpo-28469: timeit now uses the sequence 1, 2, 5, 10, 20, 50,... instead
    https://hg.python.org/cpython/rev/8e6cc952adc6

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