#! 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;


##</code><code>##

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

my %result : shared;

sub process {
    my $Q = shift;
    while( my $number = $Q->dequeue ) {
        my $factorial = factorial($number);
        lock %result;
        $result{$number} = $factorial->bstr;
    }
}

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

my $start = time;

my $Q = new Thread::Queue;
$Q->enqueue( 1000..2000, (undef) x 4 );

my @threads = map { threads->create( \&process, $Q ); } 1 .. 4;

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


##</code><code>##

#! perl -slw
use strict;
use Math::BigInt;
use Time::HiRes qw[ time ];
use feature qw(say);

my $start = time;

my $bn = Math::BigInt->bfac( 1000 );
my %result;
$result{ 1000 } = $bn->bstr;

for( 1001..2000 ) {
    $bn *= $_;
    $result{ $_ } = $bn->bstr;
}

my $end = time;
printf "Took %.6f seconds\n", $end - $start;