STINNER Victor added the comment:
bench_bytes_format.py: micro-benchmark testing a few formats. Some tests are
focused on the implementation of _PyBytesWriter to ensure that the optimization
is efficient.
Except of a single test (which is not really revelant, it takes less than 500
nanoseconds), all tests are faster.
The b"xxxxxx %s" % b"y" test confirms that the optimization disabling
overallocation for the last write is effective.
Results:
Common platform:
Timer info: namespace(adjustable=False,
implementation='clock_gettime(CLOCK_MONOTONIC)', monotonic=True,
resolution=1e-09)
Python unicode implementation: PEP 393
CPU model: Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz
Platform: Linux-4.1.6-200.fc22.x86_64-x86_64-with-fedora-22-Twenty_Two
CFLAGS: -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g
-fwrapv -O3 -Wall -Wstrict-prototypes
Timer: time.perf_counter
Bits: int=32, long=64, long long=64, size_t=64, void*=64
Platform of campaign orig:
SCM: hg revision=1aae9b6a6929 tag=tip branch=default date="2015-10-09 01:34
-0400"
Timer precision: 64 ns
Python version: 3.6.0a0 (default:1aae9b6a6929, Oct 9 2015, 11:33:56) [GCC 5.1.1
20150618 (Red Hat 5.1.1-4)]
Date: 2015-10-09 11:34:11
Platform of campaign writer:
SCM: hg revision=fc2c11a19ae1+ tag=tip branch=default date="2015-10-09 11:48
+0200"
Timer precision: 61 ns
Python version: 3.6.0a0 (default:fc2c11a19ae1+, Oct 9 2015, 12:16:16) [GCC
5.1.1 20150618 (Red Hat 5.1.1-4)]
Date: 2015-10-09 12:16:31
---------------------------+------------+--------------
use smaller buffer | orig | writer
---------------------------+------------+--------------
b"hello %s" % b"world" | 13 ns (*) | 12 ns (-5%)
b"hello %-100s" % b"world" | 158 ns (*) | 98 ns (-38%)
b"x=%d" % 123 | 13 ns (*) | 12 ns
b"x=%f" % 1.2 | 13 ns (*) | 13 ns
b"x=%100d" % 123 | 156 ns (*) | 166 ns (+7%)
---------------------------+------------+--------------
Total | 353 ns (*) | 301 ns (-15%)
---------------------------+------------+--------------
-------------------------------------------------+-------------+---------------
"hello %s" % long_string | orig | writer
-------------------------------------------------+-------------+---------------
fmt = b"hello %s"; arg = b"x" * 10; fmt % arg | 98 ns (*) | 86 ns (-12%)
fmt = b"hello %s"; arg = b"x" * 100; fmt % arg | 85 ns (*) | 87 ns
fmt = b"hello %s"; arg = b"x" * 10**3; fmt % arg | 298 ns (*) | 208 ns (-30%)
fmt = b"hello %s"; arg = b"x" * 10**5; fmt % arg | 4.8 us (*) | 4.39 us (-9%)
-------------------------------------------------+-------------+---------------
Total | 5.28 us (*) | 4.77 us (-10%)
-------------------------------------------------+-------------+---------------
---------------------------------------+-------------+---------------
b"xxxxxx %s" % b"y" | orig | writer
---------------------------------------+-------------+---------------
fmt = b"x" * 10 + b"%s"; fmt % b"y" | 99 ns (*) | 81 ns (-18%)
fmt = b"x" * 100 + b"%s"; fmt % b"y" | 189 ns (*) | 87 ns (-54%)
fmt = b"x" * 10**3 + b"%s"; fmt % b"y" | 1.12 us (*) | 209 ns (-81%)
fmt = b"x" * 10**5 + b"%s"; fmt % b"y" | 88.4 us (*) | 8.49 us (-90%)
---------------------------------------+-------------+---------------
Total | 89.8 us (*) | 8.87 us (-90%)
---------------------------------------+-------------+---------------
----------------------------------------------------------+-------------+---------------
%f | orig |
writer
----------------------------------------------------------+-------------+---------------
n = 200; fmt = b"%f" * n; arg = tuple([1.2]*n); fmt % arg | 37.2 us (*) | 29.6
us (-21%)
----------------------------------------------------------+-------------+---------------
------------------------------------------------------------+-------------+---------------
%i | orig |
writer
------------------------------------------------------------+-------------+---------------
n = 200; fmt = b"%f" * n; arg = tuple([12345]*n); fmt % arg | 49.4 us (*) |
42.8 us (-13%)
------------------------------------------------------------+-------------+---------------
-------------------------+-------------+---------------
Summary | orig | writer
-------------------------+-------------+---------------
use smaller buffer | 353 ns (*) | 301 ns (-15%)
"hello %s" % long_string | 5.28 us (*) | 4.77 us (-10%)
b"xxxxxx %s" % b"y" | 89.8 us (*) | 8.87 us (-90%)
%f | 37.2 us (*) | 29.6 us (-21%)
%i | 49.4 us (*) | 42.8 us (-13%)
-------------------------+-------------+---------------
Total | 182 us (*) | 86.3 us (-53%)
-------------------------+-------------+---------------
----------
Added file: http://bugs.python.org/file40726/bench_bytes_format.py
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue25349>
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