Mark Dickinson <dicki...@gmail.com> added the comment: For some ranges of inputs, it may make sense to use the apparently naive implementation `factorial(n) // factorial(k) // factorial(n - k)`. The current factorial implementation is significantly optimised, and using it directly may be faster than using an iterative solution.
Here are some timings (Python 3.7.1, macOS 10.13), using Raymond's `comb` function from msg331257: In [5]: %timeit comb(1000, 600) 186 µs ± 442 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each) In [6]: %timeit factorial(1000) // factorial(600) // factorial(400) 97.8 µs ± 256 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each) In [7]: %timeit factorial(1000) // (factorial(600) * factorial(400)) 91.1 µs ± 789 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each) But that's just one set of inputs, on one system; your results may vary. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35431> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
