From: masa@...
Date: 2001-05-17T03:23:30+09:00
Subject: [ruby-talk:15305] Re: Discussion on new Ruby features

>From: Christian Szegedy <szegedy@or.uni-bonn.de>
>Subject: [ruby-talk:15262] Re: Discussion on new Ruby features

> The main application of such a feature would not be the string class,
> but mathematical classes such as Matrix and Polynomial,...

I considerd such an issue for NArray.

> Or Take for example:
> x = (a+b)*(c+d) 
> It could be mapped as (a.dup += b)*=(c.dup+=d),

For NArray, this is written as;

  x = (a.dup.add!(b)).mul!(c.dup.add!(d))

But it does not always improve speed;

  % ruby bang.rb 1
  calculating x = (a+b)*(c+d) ...
   Time: 3.09 sec

  % ruby bang.rb 2
  calculating x = (a.dup.add!(b)).mul!(c.dup.add!(d)) ...
   Time: 3.47 sec

  % ruby bang.rb 3
  calculating x = (a+b).mul!(c+d) ...
   Time: 2.85 sec

-- bang.rb --
require "narray"

REPEAT = 10

def bench_time(n=REPEAT)
  t1 = Time.times.utime
   for i in 1..n
     yield
   end
  t2 = Time.times.utime 
  puts " Time: %.2f sec\n\n" % [t2-t1]
end

n = 1_000_000
a = NArray.float(n).indgen!
b = NArray.float(n).indgen!
c = NArray.float(n).indgen!
d = NArray.float(n).indgen!

case ARGV[0]
when "1"
  print "calculating x = (a+b)*(c+d) ...\n"
  bench_time{ x = (a+b)*(c+d) }
when "2"
  print "calculating x = (a.dup.add!(b)).mul!(c.dup.add!(d)) ...\n"
  bench_time{ x = (a.dup.add!(b)).mul!(c.dup.add!(d)) }
when "3"
  print "calculating x = (a+b).mul!(c+d) ...\n"
  bench_time{ x = (a+b).mul!(c+d) }
end

--
Masa Tanaka