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imghdr test order makes it slow #47674

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biny mannequin opened this issue Jul 22, 2008 · 6 comments
Closed

imghdr test order makes it slow #47674

biny mannequin opened this issue Jul 22, 2008 · 6 comments
Labels
performance Performance or resource usage stdlib Python modules in the Lib dir

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@biny
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Mannequin

biny mannequin commented Jul 22, 2008

BPO 3424
Nosy @benjaminp
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  • current: Unoptimized
  • optimized: optimized
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    GitHub fields:

    assignee = None
closed_at = <Date 2008-08-16.16:29:28.786>
created_at = <Date 2008-07-22.09:30:38.898>
labels = ['library', 'performance']
title = 'imghdr test order makes it slow'
updated_at = <Date 2008-08-16.16:29:28.785>
user = 'https://bugs.python.org/biny'

    bugs.python.org fields:

    activity = <Date 2008-08-16.16:29:28.785>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2008-08-16.16:29:28.786>
closer = 'benjamin.peterson'
components = ['Library (Lib)']
creation = <Date 2008-07-22.09:30:38.898>
creator = 'biny'
dependencies = []
files = ['10958', '10959']
hgrepos = []
issue_num = 3424
keywords = []
message_count = 6.0
messages = ['70142', '70146', '70168', '70507', '70649', '71224']
nosy_count = 2.0
nosy_names = ['benjamin.peterson', 'biny']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue3424'
versions = ['Python 2.5']
    @biny
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    biny mannequin commented Jul 22, 2008

    The order of tests in imghdr makes it slow in common cases. Even without
    any statistics it is quite easy to see that jpeg is the most common
    format. In imghdr only bmp and png are after it. Also, should png really
    be the last one?

    Nearly all digital cameras produce jpegs and handling such images is one
    big use case for this module.

    Changing the test order should be easy and have big effect in common use
    cases.

    @biny biny mannequin added stdlib Python modules in the Lib dir performance Performance or resource usage labels Jul 22, 2008
    @benjaminp
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    Do you have any benchmarks to prove this with? IMO, the difference would
    be extremely insignificant.

    @biny
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    biny mannequin commented Jul 23, 2008

    Naturally it requires a big amount of files. Getting big amount of jpegs
    is easy. Getting big amount of pbms or rgbs is not so easy.

    I'll attach two profiling runs showing some difference when test_jpeg
    and test_exif are moved to be the first tests. The beginnings those
    outputs show the return value counts.

    @benjaminp
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    Ok. Would you like to propose an alternate order?

    @biny
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    biny mannequin commented Aug 3, 2008

    jpeg
    exif
    png
    gif
    tiff

    and then the rest

    @benjaminp
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    Done in r65713.

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