Serhiy Storchaka added the comment: > Why are the two Py_ABS() calls at the end needed when we start off the > algorithm with long_abs()?
Because long_abs()'s are omitted for small enough numbers (common case). So we avoid a copying for negative numbers or int subclasses. > I guess that's why you added the pure Euclidean implementation Euclidean algorithm is required step at the end of Lehmer algorithm. > It's 4% faster than the Euclidean code for the fractions benchmark > when using 30 bit digits, but (surprisingly enough) about the same speed > with 15 bit digits. May be because Lehmer code uses 64-bit computation for 30-bit digits, and Euclidean code always uses 32-bit computation. > The difference for big numbers is substantial though: 1000-bit integers are big, but can be encountered in real word (e.g. in cryptography). So may be there is need in Lehmer algorithm. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue22486> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
