View of /trunk/pg/lib/PGrandom.pm

    1 
    2 
    3 
    4 package PGrandom;
    5 
    6 
    7 use strict;
    8 
    9 my $multiplier = 69069;
   10 
   11 my $translate = 1;
   12 
   13 my $modulus = 2**32;
   14 
   15 sub new {
   16   my $class       = shift;
   17   my $seed      = shift;
   18 
   19   $seed    = 1 unless defined($seed);
   20   my $original_seed = $seed;
   21   $seed    =  mod ($multiplier * $seed + $translate, $modulus);
   22   my $self = { 'seed'       => $seed,
   23                'original_seed'  => $original_seed,  # this and the next value are largely for debugging
   24                'number_of_calls'  => 1                # there is always one call to set the seed.
   25   };
   26 
   27   bless $self, $class;
   28 
   29   return $self;
   30 }
   31 sub mod {   # for some reason perl's % doesn't seem to work for large numbers?
   32     my $a = shift;
   33     my $b = shift;
   34     $a - int($a/$b)*$b;
   35 }
   36 
   37 sub random {
   38   my $self  = shift;
   39   my $begin = shift;
   40   my $end   = shift;
   41   my $incr  = shift;
   42   my $out;
   43   $self->{'number_of_calls'}++;
   44   $incr     = 1 unless defined($incr);
   45   my $seed = $self->{'seed'};
   46   my $new_seed = mod ($multiplier * $seed + $translate, $modulus) ;
   47   $self->{'seed'} = $new_seed;
   48   unless ( $incr <= 0 ) {
   49     $out = $begin +$incr*int( ($new_seed/($modulus))*(int( ($end-$begin)/$incr) +1) );
   50   } else {          # if $incr is less than zero return "continuous" distribution
   51     $out = $begin + ($end-$begin)*$new_seed/$modulus;
   52   }
   53   $out;
   54 
   55 }
   56 sub rand {
   57   my $self  = shift;
   58   my $end   = shift;
   59   $end = 1 unless defined($end);
   60   $self->random(0,$end,0);
   61 }
   62 
   63 sub srand {
   64   my $self = shift;
   65   my $new_seed = shift;
   66   $self->{'original_seed'} = $new_seed;
   67     $new_seed= mod ($multiplier * $new_seed + $translate, $modulus) ;   # reset the seed
   68     $self->{'number_of_calls'}=1;
   69     $self->{'seed'} = $new_seed;
   70 }
   71 sub seed {  #synonym for srand
   72   my $self = shift;
   73   $self->srand(@_);
   74 }
   75 
   76 1;