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bpo-32677: Optimize str.isascii()#5356

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methane merged 2 commits intopython:masterfrom
methane:optimize-str-isascii
Jan 28, 2018
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bpo-32677: Optimize str.isascii()#5356
methane merged 2 commits intopython:masterfrom
methane:optimize-str-isascii

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@methane methane commented Jan 27, 2018 •
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vstinner commented Jan 27, 2018

Can you try a microbenchmark of bytes object of 256 bytes and 1 MB?

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methane commented Jan 27, 2018 

$ ./python -m perf timeit --compare-to=`pwd`/python-master -s 'b=b"x"*(1024**2)' -- 'b.isascii()'
python-master: ..................... 679 us +- 0 us
python: ..................... 84.9 us +- 0.0 us

Mean +- std dev: [python-master] 679 us +- 0 us -> [python] 84.9 us +- 0.0 us: 7.99x faster (-87%)

$ ./python -m perf timeit --compare-to=`pwd`/python-master -s 'b=b"x"*256' -- 'b.isascii()'
python-master: ..................... 228 ns +- 1 ns
python: ..................... 76.8 ns +- 1.8 ns

Mean +- std dev: [python-master] 228 ns +- 1 ns -> [python] 76.8 ns +- 1.8 ns: 2.97x faster (-66%)

$ ./python -m perf timeit --compare-to=`pwd`/python-master -s 'b=b"x"*39' -- 'b.isascii()'
python-master: ..................... 81.5 ns +- 2.1 ns
python: ..................... 64.3 ns +- 1.1 ns

Mean +- std dev: [python-master] 81.5 ns +- 2.1 ns -> [python] 64.3 ns +- 1.1 ns: 1.27x faster (-21%)

@methane methane changed the title [wip] bpo-32677: Optimize str.isascii() bpo-32677: Optimize str.isascii() Jan 27, 2018
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vstinner approved these changes Jan 27, 2018
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LGTM.

Impressive benchmark, it's really 8x faster for long strings. 20 ns faster on 80 ns for short strings is also nice to have!

@methane methane merged commit bea5706 into python:master Jan 28, 2018
@methane methane deleted the optimize-str-isascii branch January 28, 2018 00:59
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