From: Ken Bloom <kbloom@...>
Date: 2006-10-26T13:05:05+09:00
Subject: Re: simple math question

On Thu, 26 Oct 2006 01:19:08 +0000, Jeffrey Schwab wrote:

> Paul Lutus wrote:
>> Brad Tilley wrote:
>> 
>>> Thanks for all the examples guys! Being Ruby, I thought there might be
>>> some super simple method that just magically did this. I'll stick with
>>> the old-fashioned modulo test.
>> 
>> If speed matters, the modulo test is way slower than testing the LSB.
> 
> Do you mean on a specific architecture, or is there a Ruby-specific 
> reason for one to be slower than the other?

Modulo uses division hardware, which is slower than the hardware for
bitwise operations. Most C compilers know how to optimize this sort of
thing when it's known in advance that you're doing mod 2. I doubt Ruby's
that smart.

--Ken

-- 
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/
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