#! perl -slw
use strict;
use threads;
use threads::shared;
use Thread::Semaphore;
use Math::BigInt;
use Time::HiRes qw[ time ];
use Data::Dump qw[ pp ];
use feature qw(say);

my %result : shared;
my $semaphore = Thread::Semaphore->new(4);

sub process {
    my $number    = shift;
    my $factorial = factorial($number);
    lock %result;
    $result{$number} = $factorial->bsstr;
    $semaphore->up;
}

sub factorial {
    my $number = shift;
    Math::BigInt->bfac($number);
}

my @numbers = ( 1000..2000 );

my $start = time;
my @threads = map {
    $semaphore->down;
    threads->create( \&process, $_ );
} @numbers;

$_->join for @threads;
my $end = time;
printf "Took %.6f seconds\n", $end - $start;