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Re: Bitshifts and "And" vs Floor-division and Modular

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On Sep 7, 5:01 am, jimbo1qaz <jimmyli1...@gmail.com> wrote:
> Is it faster to use bitshifts or floor division? And which is better, & or %?
> All divisors and mods are power of 2, so are binary operations faster? And are they considered bad style?

On an 8086/8088 a MUL (multiply) instruction was of the order of 100
clocks and a DIV nearly 200 compared to ADD, OR etc which were
something like 8 (IIRC -- this is decades-stale knowledge)
On most modern processors (after the pentium) the difference has
mostly vanished.  I cant find a good data sheet to quote though -- one
of the sad things about modern processors is that the clocks which
were politely offered by intel earlier have now stopped presumably
because cache-(in)coherence, pipelining etc are more likely to
dominate the number of clocks than the specific instruction.

This question is interesting to a programmer but meaningless at the
python level (as others have pointed out).  If it still interests you,
work at the C (or still better assembly) level and use a more
finegrained timer measure -- the finest being the RDTSC instruction.

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Bitshifts and "And" vs Floor-division and Modular jimbo1qaz <jimmyli1528@gmail.com> - 2012-09-06 17:01 -0700
  Re: Bitshifts and "And" vs Floor-division and Modular Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-07 01:30 +0100
    Re: Bitshifts and "And" vs Floor-division and Modular jimbo1qaz <jimmyli1528@gmail.com> - 2012-09-06 18:05 -0700
    Re: Bitshifts and "And" vs Floor-division and Modular jimbo1qaz <jimmyli1528@gmail.com> - 2012-09-06 18:05 -0700
  Re: Bitshifts and "And" vs Floor-division and Modular jimbo1qaz <jimmyli1528@gmail.com> - 2012-09-06 18:30 -0700
    Re: Bitshifts and "And" vs Floor-division and Modular Dave Angel <d@davea.name> - 2012-09-06 21:46 -0400
    Re: Bitshifts and "And" vs Floor-division and Modular Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-07 02:23 +0000
  Re: Bitshifts and "And" vs Floor-division and Modular Dave Angel <d@davea.name> - 2012-09-06 21:36 -0400
  Re: Bitshifts and "And" vs Floor-division and Modular Terry Reedy <tjreedy@udel.edu> - 2012-09-06 21:53 -0400
  Re: Bitshifts and "And" vs Floor-division and Modular Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-07 02:00 +0000
    Re: Bitshifts and "And" vs Floor-division and Modular Grant Edwards <invalid@invalid.invalid> - 2012-09-07 14:19 +0000
  Re: Bitshifts and "And" vs Floor-division and Modular rusi <rustompmody@gmail.com> - 2012-09-06 20:38 -0700
    Re: Bitshifts and "And" vs Floor-division and Modular Paul Rubin <no.email@nospam.invalid> - 2012-09-06 21:32 -0700
      Re: Bitshifts and "And" vs Floor-division and Modular rusi <rustompmody@gmail.com> - 2012-09-07 09:59 -0700
        Re: Bitshifts and "And" vs Floor-division and Modular Dave Angel <d@davea.name> - 2012-09-07 13:12 -0400

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