[Python-Dev] Tunable parameters in dictobject.c (was dictnotes.txt out of date?) (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Mon Jun 18 21:35:49 CEST 2012

On Mon, 18 Jun 2012 21:31:27 +0200 Maciej Fijalkowski <fijall at gmail.com> wrote:

On Mon, Jun 18, 2012 at 5:04 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:

> On Mon, 18 Jun 2012 15:28:24 +0100 > Mark Shannon <mark at hotpy.org> wrote: > > > > But do they? The results of benchmarking would seem to suggest (at least > > on my test machine) that overly-sparse dicts are slower. > > Possibly due to increased cache misses. > > Or, at least, they are not faster. See the synthetic experiments in > http://bugs.python.org/issue10408 > > That said, Raymond might have witnessed different results at the time. > Hardware evolves quickly and the parameters change (memory latency > today is at least 50+ CPU cycles, which is quite a lot of wasted work on > a pipelined superscalar CPU). > > Regards > > Antoine. > > More like 200-500 CPU cycles on modern CPUs.

You are right. I was thinking 50 nanoseconds (which for a - relatively high-end - 3GHz CPU puts us at 150 cycles).

Regards

Antoine.

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