use strict;
use Benchmark;
use vars '@array';

# The Fisher-Yates Shuffle 
#
#    my $arrayref = shift;
#    my $index = @$arrayref;
#    while ( $index-- ) 
#    {
#        my $newloc = int rand (1+$i);
#        next if $index == $newloc;
#        @$arrayref[$index, $newloc] = @$arrayref[$newloc, $index];
#    }

@array = (1..100_000); # An array to be shuffled. 

# Rather then pass in a ref to the array, just shuffle the array in place.
timethese( 100, {
	'BRANCH'  => sub {
			my $i=@array; 
			while($i--){
				my $j=int rand(1+$i);
				next if $i==$j;  ### This is the line being tested.
				@array[$i, $j]=@array[$j, $i]
			}},
	'WITHOUT' => sub {
			my $i=@array; 
			while($i--){
				my $j=int rand(1+$i); 
				@array[$i, $j]=@array[$j, $i]
			}},
	} );

# Benchmark: timing 100 iterations of BRANCH, WITHOUT...
#  BRANCH: 73 wallclock secs (73.43 usr +  0.00 sys = 73.43 CPU) @  1.36/s (n=100)
# WITHOUT: 67 wallclock secs (67.02 usr +  0.00 sys = 67.02 CPU) @  1.49/s (n=100)

# Benchmark: timing 1000 iterations of BRANCH, WITHOUT...
#  BRANCH: 727 wallclock secs (726.67 usr +  0.00 sys = 726.67 CPU) @  1.38/s (n=1000)
# WITHOUT: 668 wallclock secs (667.78 usr +  0.02 sys = 667.80 CPU) @  1.50/s (n=1000)