STINNER Victor added the comment: pow2_specialized.patch: here is a different approach, a little bit faster. I wrote a dedicated long_pow2() function which computes 2**k.
Arguments in favor of pow2_specialized.patch instead of pow2.patch: - it's a little bit faster - don't touch long_lshift(), so there is no risk of performance regression - it becomes easier to implement #21419 optimization: use calloc() instead of malloc() for very large power of 2, to avoid allocating physical memory pages for zeros Results of bench_pow2.py comparing original Python, pow2.pathc and pow2_specialized.patch: Common platform: Platform: Linux-3.13.9-200.fc20.x86_64-x86_64-with-fedora-20-Heisenbug Timer info: namespace(adjustable=False, implementation='clock_gettime(CLOCK_MONOTONIC)', monotonic=True, resolution=1e-09) Python unicode implementation: PEP 393 Bits: int=32, long=64, long long=64, size_t=64, void*=64 Timer: time.perf_counter CPU model: Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz CFLAGS: -Wno-unused-result -Werror=declaration-after-statement -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes Platform of campaign orig: SCM: hg revision=62438d1b11c7 tag=tip branch=default date="2014-05-02 23:26 +0200" Date: 2014-05-03 14:42:56 Timer precision: 46 ns Python version: 3.5.0a0 (default:62438d1b11c7, May 3 2014, 14:41:50) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] Platform of campaign pow2: SCM: hg revision=62438d1b11c7+ tag=tip branch=default date="2014-05-02 23:26 +0200" Python version: 3.5.0a0 (default:62438d1b11c7+, May 3 2014, 14:41:13) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] Date: 2014-05-03 14:41:21 Timer precision: 51 ns Platform of campaign pow2_specialized: SCM: hg revision=62438d1b11c7+ tag=tip branch=default date="2014-05-02 23:26 +0200" Date: 2014-05-03 14:40:26 Python version: 3.5.0a0 (default:62438d1b11c7+, May 3 2014, 14:40:18) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] Timer precision: 46 ns ---------------+--------------------+--------------+----------------- Tests | orig | pow2 | pow2_specialized ---------------+--------------------+--------------+----------------- 2 ** 0 | 39 ns (*) | 44 ns (+11%) | 41 ns 2 ** 1 | 264 ns (+531%) | 62 ns (+48%) | 42 ns (*) 2 ** 3 | 269 ns (+554%) | 62 ns (+50%) | 41 ns (*) 2 ** 5 | 269 ns (+560%) | 62 ns (+51%) | 41 ns (*) 2 ** 10 | 279 ns (+410%) | 63 ns (+15%) | 55 ns (*) 2 ** 15 | 299 ns (+460%) | 62 ns (+16%) | 53 ns (*) 2 ** 20 | 287 ns (+426%) | 62 ns (+14%) | 55 ns (*) 2 ** 25 | 302 ns (+466%) | 62 ns (+16%) | 53 ns (*) 2 ** 28 | 293 ns (+438%) | 62 ns (+14%) | 55 ns (*) 2 ** (2 ** 0) | 264 ns (+549%) | 62 ns (+52%) | 41 ns (*) 2 ** (2 ** 1) | 264 ns (+524%) | 62 ns (+48%) | 42 ns (*) 2 ** (2 ** 3) | 263 ns (+548%) | 62 ns (+52%) | 41 ns (*) 2 ** (2 ** 5) | 283 ns (+346%) | 68 ns (+8%) | 63 ns (*) 2 ** (2 ** 10) | 715 ns (+950%) | 68 ns (*) | 69 ns 2 ** (2 ** 15) | 89.6 us (+51109%) | 175 ns (*) | 177 ns 2 ** (2 ** 20) | 3.89 ms (+100603%) | 3.86 us (*) | 3.86 us 2 ** (2 ** 25) | 152 ms (+66557%) | 240 us (+5%) | 228 us (*) 2 ** (2 ** 28) | 1.35 sec (+33851%) | 3.99 ms (*) | 3.99 ms ---------------+--------------------+--------------+----------------- Total | 1.51 sec (+35664%) | 4.23 ms | 4.22 ms (*) ---------------+--------------------+--------------+----------------- ---------- Added file: http://bugs.python.org/file35145/pow2_specialized.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue21420> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
