P:\test\MJD>ack1 9
    Ack(3,9): 4093
    78.843 83.671 0 0

##</code><code>##

P:\test\MJD>timethis "c:javac ackermann.java && java ackermann 9"

TimeThis :  Command Line :  c:javac ackermann.java && java ackermann 9
TimeThis :    Start Time :  Fri Sep 02 22:01:28 2005

Ack(3,9): 4093

TimeThis :  Command Line :  c:javac ackermann.java && java ackermann 9
TimeThis :    Start Time :  Fri Sep 02 22:01:28 2005
TimeThis :      End Time :  Fri Sep 02 22:01:29 2005
TimeThis :  Elapsed Time :  00:00:01.031

##</code><code>##

use Memoize;
memoize("Ack");
my $count = 0;
sub Ack {
    $count++;
    return $_[0] ? ($_[1] ? Ack($_[0]-1, Ack($_[0], $_[1]-1))
    : Ack($_[0]-1, 1)) : $_[1]+1;
}

my $NUM = $ARGV[0];
$NUM = 1 if ($NUM < 1);
my $ack = Ack(3, $NUM);
print "Ack(3,$NUM): $ack";
#print times;
print "Ack() called $count times";

##</code><code>##

P:\test\MJD>ack1 9
Ack(3,9): 4093
79.187 83.093 0 0
Ack() called 11,164,370 times

P:\test\MJD>ack2 9
Ack(3,9): 4093
0.046000
Ack() called 12,294 times