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

[Eric Snow]

On Sep 15, 2016 06:06, "Serhiy Storchaka" <storchaka at gmail.com> wrote:
> Python 3.5: 10 loops, best of 3: 33.5 msec per loop
> Python 3.6: 10 loops, best of 3: 37.5 msec per loop
>
> These results look surprisingly and inexplicably to me. I expected that
even if there is some performance regression in the lookup or modifying
operation, the iteration should not be slower.

My understanding is that the all-int-keys case is an outlier.  This is due
to how ints hash, resulting in fewer collisions and a mostly
insertion-ordered hash table.  Consequently, I'd expect the above
microbenchmark to give roughly the same result between 3.5 and 3.6, which
it did.

-eric
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