#!/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__