STINNER Victor <victor.stin...@gmail.com> added the comment: So, do you have any comment or complain? Or can I commit the patch? Le 24 mai 2012 11:57, "STINNER Victor" <rep...@bugs.python.org> a écrit :
> > STINNER Victor <victor.stin...@gmail.com> added the comment: > > >> For Python 3.3, _PyUnicodeWriter API is faster than the Py_UCS4 buffer > API and PyAccu API in quite all cases, with a speedup between 30% and 100%. > But there are some cases where the _PyUnicodeWriter API is slower: > > > > Perhaps most of these problems can be solved if instead of the boolean > > flag (overallocate/no overallocate) to use the Py_ssize_t parameter that > > indicates by how much should you overallocate (it is the length of the > > suffix in the format). > > There is not only a flag (flags.overallocate): there is also the > min_length, which is used and helps for str%args and str.format(args). > > My patch contains a lot of "tricks" to limit overallocation, e.g. > don't overallocate if we are writing the last part of the output. > > Computing exactly the size of the buffer gives the best performance > because it avoids a resize in _PyUnicodeWriter_Finish(). I tried for > example to modify PyUnicode_Format() to parse the format string twice: > first to compute the size of the output buffer, second to write > characters. In my experience, parsing the format string twice is more > expensive than reallocating the buffer (PyUnicode_READ is expensive), > especially on short and simple format strings. > > I tried different methods to allocate the buffer of _PyUnicodeWriter: > change the overallocation factor (0%, 25%, 50%, 100%), only > overallocate +100 characters, etc. But I failed to find something > better than the proposed patch. > > At least I can say than always disabling overallocation slows done > many cases: when there is a suffix after an argument, or when there > are more than one argument. > > Feel free to experiment other methods to estimate the size of the output > buffer. > > ---------- > > _______________________________________ > Python tracker <rep...@bugs.python.org> > <http://bugs.python.org/issue14744> > _______________________________________ > ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue14744> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
