[issue14874] Faster charmap decoding

[Roundup Robot]

Roundup Robot  added the comment:

New changeset 8f3a5308f50b by Antoine Pitrou in branch 'default':
Issue #14874: Restore charmap decoding speed to pre-PEP 393 levels.
http://hg.python.org/cpython/rev/8f3a5308f50b

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[issue14874] Faster charmap decoding

[Antoine Pitrou]

Antoine Pitrou  added the comment:

Thank you for the patch! Now pushed to 3.3.

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resolution:  -> fixed
stage: patch review -> committed/rejected
status: open -> closed

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[issue14874] Faster charmap decoding

[Antoine Pitrou]

Changes by Antoine Pitrou :


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[issue14874] Faster charmap decoding

[Antoine Pitrou]

Changes by Antoine Pitrou :


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stage:  -> patch review

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[issue14874] Faster charmap decoding

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


Added file: http://bugs.python.org/file25666/bench-diff.py

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[issue14874] Faster charmap decoding

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


Added file: http://bugs.python.org/file25665/charmapdecodebench.py

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[issue14874] Faster charmap decoding

[Serhiy Storchaka]

New submission from Serhiy Storchaka :

Charmap decoders are not as important as UTF decoders, but are still widely 
used. In Python 3.3 with PEP 393 they slowed down 4x. The proposed patch 
restores the performance.

Optimized only the most common case, when the decoder is specified by the UCS2 
table with length >= 256. Map-based decoders translated to table-based. UCS1 
tables widened to UCS2 by adding 257th fake characters.

Benchmark results:

 3.2   3.3(vanilla)  3.3(patched)

cp1251'A'*1  111 (+10%)31 (+294%)122
cp1251'\xa0'*1   111 (+8%) 29 (+314%)120
cp1251'\u0402'*1 111 (+6%) 25 (+372%)118

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components: Interpreter Core, Unicode
files: decode_charmap.patch
keywords: patch
messages: 161301
nosy: ezio.melotti, haypo, lemburg, pitrou, storchaka
priority: normal
severity: normal
status: open
title: Faster charmap decoding
type: performance
versions: Python 3.3
Added file: http://bugs.python.org/file25664/decode_charmap.patch

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