#!/usr/bin/perl -w
# Blum Blum Shub random number generator
#
# 2014-03-02

use strict;

my $x = 3;
#my $m = 8999 * 9001;  # Period = 5102
#my $m = 11117 * 11119;  # Period = 794
#my $m = 13337 * 13339;  # Period = 14997
#my $m = 11117 * 47777;  # Period = 49241
#my $m = 32717 * 32719;  # Period = 245342
my $m = 10007 * 11117;  # Period = 330134

my %seen = ();
my @freq = (0, 0, 0, 0);
for(my $i = 0; $i < 1000000; $i++)
{
   if( exists $seen{$x} )
   {
      print "Period = $i\n";
      last;
   }
   $seen{$x} = 1;
   $freq[$x % 4]++;
   $x = ($x * $x) % $m;
}

for(my $i = 0; $i < 4; $i++)
{
   print "freq[$i] = $freq[$i]\n";
}