Re: [MacPerl] random function immune to windows

[Dr. Neil Gunther]

Here's a P-RNG that I have to work well.

--njg

#! /usr/bin/perl -w
#
# yapr.pl - Yet another portable RNG
#
# Created by NJG  09:14:16 AM Thu, Feb 20, 2003

sub rand_val {
    use integer; 

    use constant ac =>      16807;  # Multiplier
    use constant mc => 2147483647;  # Modulus
    use constant qc =>     127773;  # m div a
    use constant rc =>       2836;  # m mod a
    my $x_div_q;                     # x divided by q
    my $x_mod_q;                     # x modulo q
    my $x_new;                       # New x value
    
    # RNG using integer arithmetic
    $x_div_q = $x / qc;
    $x_mod_q = $x % qc;
    $x_new = (ac * $x_mod_q) - (rc * $x_div_q);
    if ($x_new > 0) {
        $x = $x_new;
    }
    else {
        $x = $x_new + mc;
    }
    
    # Return a random value between 0.0 and 1.0
    no integer;
    return($x / mc);
}


sub test_rv {
    $x = 1; # set seed value to 1
    for ($i = 0; $i < 10000; $i++) {$rv = rand_val();}
    print "Thousandth iterate should be 1043618065: $x\n";
    print "Thousandth random variate: $rv\n";
    print "\n";
}


test_rv();

___________________________________________________________________________

PERFORMANCE DYNAMICS COMPANY(sm)              http://www.perfdynamics.com/
___________________________________________________________________________

Consulting Services                           Educational Services
4061 East Castro Valley Blvd.                 P.O. Box 1238, Magalia
Suite 110, Castro Valley                      California 95954, USA
California 94552, USA                         Bookings and registrations
FON: +1-510-537-5758                          FON: +1-530-873-0575
FAX: Dial FON (Handshakes automagically)      FAX: +1-530-873-6697
NET: [EMAIL PROTECTED]                    NET: [EMAIL PROTECTED]
___________________________________________________________________________