As I suspected that your program might be getting into an infinite loop, I have modified it slightly to display the iteration number, and the $i and $j variables, and to stop it after 40 iterations:
use strict; use warnings; my ($i, $j) = @ARGV; my $acker = ackermann($i, $j); print "A($i,$j) = $acker\n"; my $iter = 0; sub ackermann{ $iter ++; my $i = shift; my $j = shift; print "Iteration $iter: i = $i, j = $j \n"; return if $iter >= 40; if($i == 1){ undef $i; return 2**$j; } elsif($j==1){ undef $j; return ackermann($i-1,2); } else{ return ackermann($i-1, ackermann($i,$j-1)); } }
I obtain the following results:
$ perl pseudo_acker.pl 3 4 Iteration 1: i = 3, j = 4 Iteration 2: i = 3, j = 3 Iteration 3: i = 3, j = 2 Iteration 4: i = 3, j = 1 Iteration 5: i = 2, j = 2 Iteration 6: i = 2, j = 1 Iteration 7: i = 1, j = 2 Iteration 8: i = 1, j = 4 Iteration 9: i = 2, j = 16 Iteration 10: i = 2, j = 15 Iteration 11: i = 2, j = 14 Iteration 12: i = 2, j = 13 Iteration 13: i = 2, j = 12 Iteration 14: i = 2, j = 11 Iteration 15: i = 2, j = 10 Iteration 16: i = 2, j = 9 Iteration 17: i = 2, j = 8 Iteration 18: i = 2, j = 7 Iteration 19: i = 2, j = 6 Iteration 20: i = 2, j = 5 Iteration 21: i = 2, j = 4 Iteration 22: i = 2, j = 3 Iteration 23: i = 2, j = 2 Iteration 24: i = 2, j = 1 Iteration 25: i = 1, j = 2 Iteration 26: i = 1, j = 4 Iteration 27: i = 1, j = 16 Iteration 28: i = 1, j = 65536 Iteration 29: i = 1, j = inf Iteration 30: i = 1, j = inf Iteration 31: i = 1, j = inf Iteration 32: i = 1, j = inf Iteration 33: i = 1, j = inf Iteration 34: i = 1, j = inf Iteration 35: i = 1, j = inf Iteration 36: i = 1, j = inf Iteration 37: i = 1, j = inf Iteration 38: i = 1, j = inf Iteration 39: i = 1, j = inf Iteration 40: i = 1, j = inf
So, this is seemingly never going to end (or, rather, it will fail when you will have exhausted your memory). Trying to set $i or $j to 0, rather than undefining them, when they reach 1 yields the same result. I don't have time right now to try to figure out whether your so-called Ackermann formula is necessarily going to lead you to that or whether there is a bug somewhere in your code. I might look at it later. But I suspect that this line of code:
is probably not what you really want, as it is bound to explode when $i reaches 1.return 2**$j;
I'd suggest that you might want to use the real standard Ackermann function, which is something like this:
sub acker { my ($m, $n) = @_; return $n + 1 if $m ==0; return acker( $m-1, 1) if $n == 0; return acker ($m - 1, acker ($m, $n - 1)); }
But don't call it for the first of the two values larger than 3.
Or maybe you should give us the mathematical description of your so-called Ackermann function, so that we might understand what is probably wrong in your code.
In reply to Re: memory leak
by Laurent_R
in thread memory leak
by ch.sarath
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