#!/usr/bin/perl -w
use strict;
use vars qw/$size $iter/;
use Benchmark qw(cmpthese);
use Data::Dumper;

$size ||= 1000;
$iter ||= 1000;

sub FAQ_FY {
	my $array = shift;
	my $i;
	for ($i = @$array; --$i; ) {
		my $j = int rand ($i+1);
		next if $i == $j;
		@$array[$i,$j] = @$array[$j,$i];
	}
}

sub shuffl (\@) {
	my $r=pop;
	$a = $_ + rand @{$r} - $_ and @$r[$_, $a] = @$r[$a, $_]
	for (0..$#{$r});
}

my @array = 1 .. $size;

cmpthese(-1, {
    FAQ_FY	=> sub { FAQ_FY \@array },
    shuffl	=> sub { shuffl  @array },
});

my (%buckets, %d, @temp);;
my @set = qw(A B C D);

for (1 .. $iter ) {
	@temp=@set; FAQ_FY \@temp; $buckets{"@temp"}{FAQ_FY}++;
	@temp=@set; shuffl  @temp; $buckets{"@temp"}{shuffl}++;
}

print "\npermutation |  FAQ_FY |  shuffl \n";
print "----------------------------------\n";
for my $key (sort keys %buckets) {
	printf "%8.8s:   |   %4d |   %4d \n", $key,
		$buckets{$key}{FAQ_FY},
		$buckets{$key}{shuffl},

	$d{FAQ_FY}{Ex} += $buckets{$key}{FAQ_FY}; $d{FAQ_FY}{Ex2} += $buckets{$key}{FAQ_FY}**2;
	$d{shuffl}{Ex} += $buckets{$key}{shuffl}; $d{shuffl}{Ex2} += $buckets{$key}{shuffl}**2;
}
print "------------------------------------------------------\n";
printf "Std. Dev.   |  %0.3f |  %0.3f \n",
	sqrt( ($d{FAQ_FY}{Ex2} - ($d{FAQ_FY}{Ex}**2/24))/23 ),
	sqrt( ($d{shuffl}{Ex2} - ($d{shuffl}{Ex}**2/24))/23 );

__END__

##</code><code>##

C:\test>199981 -size=100 -iter=100000
Benchmark: running FAQ_FY, shuffl, each for at least 1 CPU seconds...
    FAQ_FY:  2 wallclock secs ( 1.14 usr +  0.00 sys =  1.14 CPU) @ 392.64/s (n=448)
    shuffl:  1 wallclock secs ( 1.08 usr +  0.00 sys =  1.08 CPU) @ 442.70/s (n=479)
        Rate FAQ_FY shuffl
FAQ_FY 393/s     --   -11%
shuffl 443/s    13%     --

permutation |  FAQ_FY |  shuffl
----------------------------------
 A B C D:   |   4140 |   4221
 A B D C:   |   4231 |   4211
 A C B D:   |   4205 |   4151
 A C D B:   |   4247 |   4257
 A D B C:   |   4076 |   4275
 A D C B:   |   4107 |   4244
 B A C D:   |   4207 |   4165
 B A D C:   |   4159 |   4240
 B C A D:   |   3941 |   4187
 B C D A:   |   4136 |   4116
 B D A C:   |   4158 |   4126
 B D C A:   |   4185 |   4111
 C A B D:   |   4126 |   4231
 C A D B:   |   4224 |   4122
 C B A D:   |   4135 |   4139
 C B D A:   |   4123 |   4097
 C D A B:   |   4179 |   4001
 C D B A:   |   4228 |   4175
 D A B C:   |   4295 |   4057
 D A C B:   |   4264 |   4131
 D B A C:   |   4206 |   4169
 D B C A:   |   4138 |   4239
 D C A B:   |   4167 |   4208
 D C B A:   |   4123 |   4127
------------------------------------------------------
Std. Dev.   |  72.382 |  67.643

C:\test>