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if (DEBUG) {
	require Data::Dumper::Simple;
}

our (@ISA, @EXPORT);
BEGIN {
	require Exporter;
	@ISA = qw(Exporter);
	@EXPORT = qw(bitonic_sort);  # symbols to export on request
}

# "A supercomputer is a device for turning compute-bound problems into I/O-bound problems."

=encoding utf8

=head1 NAME

Algorithm::Bitonic::Sort - Sorting numbers with Bitonic Sort

=head1 VERSION

Version 0.06

=cut

our $VERSION = '0.06';


=head1 SYNOPSIS

Use L<Algorithm::Bitonic::Sort> with the following style.

	use Algorithm::Bitonic::Sort;
	
	my @sample = (1,4,8,4,4365,2,67,33,345);
	my @result_inc = bitonic_sort( 1 ,@sample);	# incremental
	my @result_dec = bitonic_sort( 0 ,@sample);	# decremental

=head1 DESCRIPTION

Bitonic mergesort is a parallel algorithm for sorting. It is also used as a construction method for building a sorting network.
This is an Perl 5 implementation of Ken Batcher's Bitonic mergesort.

=head1 Limitation

This is a enhanced version of Bitonic Sort which removed the limitation of original version.
This module supports any amount of numbers.

The original Bitonic can only sort N numbers, which N is a power of 2.


=head1 EXPORT

bitonic_sort


=head1 SUBROUTINES

=head2 bitonic_sort

The First Parameter works as the ascending/decreasing selector.
True (1 or any true value) means ascending (incremental),
False (0 or any false value) means decreasing.

All other params will be treated as members/items to be sorted.


=cut

sub bitonic_sort {
	my $up = shift;
	say '#### Sort: '.Dumper(@_) if DEBUG;
	
	return @_ if int @_ <= 1;
	
	my $single_bit = shift @_ if @_ % 2;
	$single_bit //= 'NA';
	
	say Dumper $single_bit if DEBUG;
	
	my @num = @_;
	my @first = bitonic_sort( 1, @num[0..(@num /2 -1)] );
	my @second = bitonic_sort( 0, @num[(@num /2)..(@num -1)] );
	
	return _bitonic_merge( $up, $single_bit, @first, @second );
}

sub _bitonic_merge {
	my $up = shift;
	say '#### Merge: '.Dumper(@_) if DEBUG;
	
	my $single_bit = shift;
	say Dumper $single_bit if DEBUG;
	
	# assume input @num is bitonic, and sorted list is returned 
	return @_ if int @_ == 1;
	
	my $single_bit_2 = shift @_ if @_ % 2;
	$single_bit_2 //= 'NA';
	
	my @num = @_;
	@num = _bitonic_compare( $up, @num );
	
	my @first = _bitonic_merge( $up, 'NA', @num[0..(@num /2 -1)] );
	my @second = _bitonic_merge( $up, 'NA', @num[(@num /2)..(@num -1)] );
	
	@num = (@first, @second);
	@num = _some_sorting_algorithm( $up, $single_bit, @first, @second ) if $single_bit ne 'NA';
	@num = _some_sorting_algorithm( $up, $single_bit_2, @first, @second ) if $single_bit_2 ne 'NA';
	
	say "#####\n# Merge Result\n#####\n".Dumper(@num)  if DEBUG;
	
	return (@num);
}

sub _bitonic_compare {
	my $up = shift;
	say '#### Compare: '.Dumper(@_) if DEBUG;
	my @num = @_;
	
	my $dist = int @num /2;