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

[Serhiy Storchaka]

On 15.09.16 11:57, Victor Stinner wrote:
> 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
>
> In short: you should use my perf module.
> http://perf.readthedocs.io/en/latest/cli.html#timeit
>
> The memory layout and the hash function have a major important on such
> microbenchmark:
> https://haypo.github.io/journey-to-stable-benchmark-average.html

$ ./python -m perf timeit -s "d = dict.fromkeys(range(10**6))" -- "list(d)"

Python 3.5: Median +- std dev: 65.1 ms +- 4.9 ms
Python 3.6: Median +- std dev: 79.4 ms +- 3.9 ms

Other computer:
Python 3.5: Median +- std dev: 33.6 ms +- 0.3 ms
Python 3.6: Median +- std dev: 37.5 ms +- 0.2 ms