[Python-Dev] Python 3.6 dict becomes compact and gets a private version; and keywords become ordered (original) (raw)

Victor Stinner victor.stinner at gmail.com
Thu Sep 15 04:57:07 EDT 2016

2016-09-15 10:02 GMT+02:00 INADA Naoki <songofacandy at gmail.com>:

In my environ:

~/local/python-master/bin/python3 -m timeit -s "d = dict.fromkeys(range(10**6))" 'list(d)'

Stooooop! Please stop using timeit, it's lying!

You must not use the minimum but average or median
You must run a microbenchmark in multiple processes to test different randomized hash functions and different memory layouts

The memory layout and the hash function have a major important on such microbenchmark: https://haypo.github.io/journey-to-stable-benchmark-average.html

Both Python is built without neither --with-optimizations or make_ _profile-opt.

That's bad :-) For most reliable benchmarks, it's better to use LTO+PGO compilation.

Victor