#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use threads;
use Thread::Queue;

sub x {
    my( $str, $v1, $v2 ) = @_;
    my $result =0;
    $result += (ord substr $str, $_, 1 ) * $v1 / $v2 for 0 .. length( $str ) -1;
    return $result;
}

our $T //= 4;
our $N //= 100;
my $step = int( $N / $T );

my $now = time;
my $total :shared = 0;
my $str = 'the quick brown fox jumps over the lazy dog' x 100;

my( $start, $end ) = ( 0, $step );
my @threads = map{
    my $thread = async{
        for my $v1 ( $start .. $end ) {
            for my $v2 ( 1 .. $N ) {
                lock $total;                    ## Lock
                $total += x( $str, $v1, $v2 );  ## update
            }
        }
    };
    $start += $step +1;
    $end = $start + $step < $N ? $start + $step : $N;
    $thread;
} 1 .. $T;

$_->join for @threads;

printf STDERR "With $T threads took %.6f seconds\n", time() - $now;

print $total;

__END__
c:\test>859242-2 -T=1 -N=100
With 1 threads took 14.250000 seconds
10711649268.1623

c:\test>859242-2 -T=2 -N=100
With 2 threads took 14.297000 seconds
10711649268.1623

c:\test>859242-2 -T=3 -N=100
With 3 threads took 14.476000 seconds
10711649268.1623

c:\test>859242-2 -T=4 -N=100
With 4 threads took 14.536000 seconds
10711649268.1623


##</code><code>##

#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use threads;
use Thread::Queue;

sub x {
    my( $str, $v1, $v2 ) = @_;
    my $result =0;
    $result += (ord substr $str, $_, 1 ) * $v1 / $v2 for 0 .. length( $str ) -1;
    return $result;
}

our $T //= 4;
our $N //= 100;
my $step = int( $N / $T );

my $now = time;
my $total :shared = 0;
my $str = 'the quick brown fox jumps over the lazy dog' x 100;

my( $start, $end ) = ( 0, $step );
my @threads = map{
    my $thread = async{
        my $subtotal = 0;
        for my $v1 ( $start .. $end ) {
            for my $v2 ( 1 .. $N ) {
                $subtotal += x( $str, $v1, $v2 );  ## no lock, local update
            }
        }
        lock $total;                              ## lock
        $total += $subtotal;                      ## update
    };
    $start += $step +1;
    $end = $start + $step < $N ? $start + $step : $N;
    $thread;
} 1 .. $T;

$_->join for @threads;

printf STDERR "With $T threads took %.6f seconds\n", time() - $now;

print $total;

__END__
c:\test>859242-2 -T=1 -N=100
With 1 threads took 14.115000 seconds
10711649268.1623

c:\test>859242-2 -T=2 -N=100
With 2 threads took 7.061000 seconds
10711649268.1623

c:\test>859242-2 -T=3 -N=100
With 3 threads took 4.827000 seconds
10711649268.1624

c:\test>859242-2 -T=4 -N=100
With 4 threads took 3.732000 seconds
10711649268.1623

c:\test>859242-2 -T=5 -N=100
With 5 threads took 4.356000 seconds
10711649268.1623

##</code><code>##

c:\test>859242-2 -T=1 -N=250
With 1 threads took 87.819000 seconds
78267011685.3423

c:\test>859242-2 -T=2 -N=250
With 2 threads took 43.342000 seconds
78267011685.3423

c:\test>859242-2 -T=3 -N=250
With 3 threads took 29.350000 seconds
78267011685.3423

c:\test>859242-2 -T=4 -N=250
With 4 threads took 23.113000 seconds
78267011685.3423