On Mon, Jun 24, 2013 at 7:47 PM, Raymond Hettinger < raymond.hettin...@gmail.com> wrote:
> > > On Jun 24, 2013, at 4:07 AM, Victor Stinner <victor.stin...@gmail.com> > wrote: > > Out of curiosity, do you know (remember) how was the number 62 chosen? > Is it a compromise between memory usage and performances? 62 is > surprising because it is not a power of two :-) > > Is it to just have 64 (2+62) pointers in the structure? > > > Yes, the goal was to have the struct size be an exact multiple > of the cache line length (always a power-of-two, typically 64 bytes). > What was different then is that deques weren't indexable. > When indexing was added, the size of 62 became an > unfavorable choice because it made the division and modulo > calculation in deque_index() slower than for a power of two. > A-ha! Finally an explanation of the change. It makes intuitive sense now. I think the general feeling is that folks overreacted (perhaps confused by your silence) and that the reversal will be rolled back. Benjamin? -- --Guido van Rossum (python.org/~guido)
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