#!/usr/bin/perl

use warnings;
use strict;
use Benchmark qw/:hireswallclock cmpthese/;

my @ary = (0..5);
my $len = $#ary;
my @ary2 = @ary;
print "ARRAY: @ary2\n";  # numbers -> strings
#$_ += 0 foreach @ary2;  # stings -> numbers

#print "@ary\n";

cmpthese (-3, {
   'intervals' => sub {
        foreach my $i (0..$len-1) {
            foreach my $j ($i+1..$len) {
                my @permuted = @ary[0..$i-1, $j, $i+1..$j-1, $i, $j+1..$len];
            }
        }
    },
    'cross' => sub {
        foreach my $i (0..$len-1) {
            foreach my $j ($i+1..$len) {
                my @permuted = @ary;
                @permuted[$i, $j] = @permuted[$j, $i];
            }
        }
    },
   'intervals2' => sub {
        foreach my $i (0..$len-1) {
            foreach my $j ($i+1..$len) {
                my @permuted = @ary2[0..$i-1, $j, $i+1..$j-1, $i, $j+1..$len];
            }
        }
    },
    'cross2' => sub {
        foreach my $i (0..$len-1) {
            foreach my $j ($i+1..$len) {
                my @permuted = @ary2;
                @permuted[$i, $j] = @permuted[$j, $i];
            }
        }
    },
});

##</code><code>##

              Rate     cross2 intervals2  intervals      cross
cross2     10490/s         --        -2%       -43%       -55%
intervals2 10742/s         2%         --       -42%       -54%
intervals  18408/s        75%        71%         --       -22%
cross      23526/s       124%       119%        28%         --

##</code><code>##

           s/iter intervals2     cross2  intervals      cross
intervals2   48.2         --       -20%       -63%       -81%
cross2       38.6        25%         --       -54%       -77%
intervals    17.8       171%       117%         --       -49%
cross        9.02       434%       328%        97%         --