Robert Klemme
5/16/2008 11:12:00 AM
2008/5/16 Igor Glukharev <igvt@mail.ru>:
> Can anybody explain to me what does it mean?
>
> code ->
> a1 = Array.new(1000000)
> a2 = Array.new(1000000)
> t = Time.now
> 1000000.times { |i| a1[i] = i; a2[i] = i }
> print "1. Elapsed time: ", Time.now - t, " seconds\n"
> t = Time.now
> 1000000.times { |i| a1[i], a2[i] = i, i }
> print "2. Elapsed time: ", Time.now - t, " seconds\n"
>
> results ->
> ruby 1.8.6
> 1. Elapsed time: 0.882 seconds
> 2. Elapsed time: 11.436 seconds (!!!)
> jruby 1.1.1
> 1. Elapsed time: 1.669 seconds
> 2. Elapsed time: 2.249 seconds
I guess it's because of the intermediate arrays that are created for
the second assignment.
Btw, here's an even faster way:
13:10:16 JBoss$ /c/Temp/ass.rb
Rehearsal --------------------------------------------------------
a1[i] = i; a2[i] = i 1.188000 0.000000 1.188000 ( 1.185000)
a1[i], a2[i] = i, i 14.562000 0.000000 14.562000 ( 14.589000)
a1[i] = a2[i] = i 1.141000 0.000000 1.141000 ( 1.146000)
---------------------------------------------- total: 16.891000sec
user system total real
a1[i] = i; a2[i] = i 1.156000 0.000000 1.156000 ( 1.150000)
a1[i], a2[i] = i, i 14.750000 0.000000 14.750000 ( 14.771000)
a1[i] = a2[i] = i 1.171000 0.000000 1.171000 ( 1.173000)
13:10:59 JBoss$ cat /c/Temp/ass.rb
#!/bin/env ruby
require 'benchmark'
a1 = Array.new(1000000)
a2 = a1.dup
Benchmark.bmbm 20 do |x|
x.report "a1[i] = i; a2[i] = i" do
a1.size.times { |i| a1[i] = i; a2[i] = i }
end
x.report "a1[i], a2[i] = i, i" do
a1.size.times { |i| a1[i], a2[i] = i, i }
end
x.report "a1[i] = a2[i] = i" do
a1.size.times { |i| a1[i] = a2[i] = i }
end
end
Kind regards
robert
--
use.inject do |as, often| as.you_can - without end