From: Ara.T.Howard@...
Date: 2004-01-13T02:11:40+09:00
Subject: Re: faster integer arithmetics & arbitrary precision floating number

On Tue, 13 Jan 2004, David Garamond wrote:

> Date: Tue, 13 Jan 2004 00:09:53 +0900
> From: David Garamond <lists@zara.6.isreserved.com>
> Newsgroups: comp.lang.ruby
> Subject: faster integer arithmetics & arbitrary precision floating number
> 
> 1. Is there a way in Ruby to speed up 32bit integer arithmetics (only 
> involving numbers & sums up to 2^32-1)? I want to use Ruby for 
> summarizing network traffic logs, but it's pathetically slow compared to 
> Perl:
> 
> $ time ruby -e'1000000.times{1073741823+1073741824}'
> 
> real    0m23.693s
> user    0m5.720s
> sys     0m0.610s
> $ time perl -e'for(1..1000000){1073741823+1073741824}'
> 
> real    0m1.142s
> user    0m0.320s
> sys     0m0.050s
> 
> since 2**30 is already in the Bignum range.

if there is someway you can organized your problem into arrays (eg. collecting
the item to sum into one), narray might be the way to go, it offer blindingly
fast numerical operations:
      
  ~ > time ruby -r narray -e 'NArray.int(1000000)[true] = 1073741823+1073741824'

  real    0m0.025s
  user    0m0.010s
  sys     0m0.010s

  ~ > time perl -e'for(1..1000000){1073741823+1073741824}'

  real    0m0.128s
  user    0m0.130s
  sys     0m0.000s


in fact, the operations are fast enough that you might simply be able to use
normal ruby objects and ignore the Fixnum/Bignum distinction - which is a very
useful (accurate) abstraction:

  ~ > irb -r narray
  irb(main):001:0> (na=NArray.object(1000000))[true] = 1073741823+1073741824
  => 2147483647

  irb(main):002:0> a=Time.now; p(na.sum); b=Time.now; b.to_f - a.to_f
  2147483647000000
  => 0.882834911346436

not bad for summing a million numbers with arbitrary precision eh?

-a
-- 

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