Serhiy Storchaka added the comment: > The important reasons for this are memory use and cache thrashing, not just > CPU time.
Memory use is not an issue unless you translate hundreds of megabytes at a time. Cache trashing at the end is performance issue. The original patch is no longer applied cleanly. Here is a patch synchronized with current sources and with fixed one error. I didn't look at it closely and don't know whether it has other bugs. Here are results of microbenchmarking. $ ./python -m perf timeit -s "table = bytes(range(256)).swapcase(); data = bytearray(range(256))*1000" -- "data = data.translate(table)" Median +- std dev: 1.48 ms +- 0.02 ms $ ./python -m perf timeit -s "table = bytes(range(256)).swapcase(); data = bytearray(range(256))*1000" -- "data[:] = data.translate(table)" Median +- std dev: 1.60 ms +- 0.09 ms $ ./python -m perf timeit -s "table = bytes(range(256)).swapcase(); data = bytearray(range(256))*1000" -- "data.mtranslate(table)" Median +- std dev: 1.79 ms +- 0.07 ms In-place translate don't have benefits. It is slower that translate with creating a new copy, and even is slower that translate with copying a new copy back. ---------- Added file: http://bugs.python.org/file46137/issue17301-2.diff _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue17301> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
