#! perl -slw
use strict;
use threads;
use Time::HiRes qw[ time ];
use Data::Dump qw[ pp ];

$|++;
our $N ||= 4000;
our $T ||= 4;
our $S ||= 1;

srand( $S );
my @list = map 1|int( rand( 2**32 ) ), 1 .. $N;

my $cStart = 0;
my $cSize  = int( @list / $T );

my $start = time;
my @threads = map {
    my( $t ) = threads->create( sub{
        my( $lo, $hi ) = @_;
        use integer;
        my $tid = threads->tid;
        my @keys;
        for my $i ( 0 .. $#list ) {
            my $v = $list[ $i ];
            my $start = $i > $lo ? $i+1 : $lo;
            ( $v & $_ ) == 1 and push @keys, "$i:$_" for @list[ $start .. $hi ];
        }
        return @keys;

    }, $cStart, $_<($T) ? $cStart + $cSize + 1 : $#list );
    $cStart += $cSize;
    $t;
} 1 .. $T;


my %hash;
for( @threads ) {
    my @keys = $_->join;
    undef $hash{ $_ } for @keys;
}
printf "Took %.6f\n", time() - $start;

print 'Odd numbers in list: ', scalar @list;
print 'Pairs found: ', scalar keys %hash;

<>; pp \%hash;