src/rndgen.cxx

   1 // docm_prefix(///)
   2 /****************************************************************************
   3 *  Copyright (C) 2002 by Leo Khramov
   4 *  email:   leo@xnc.dubna.su
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License as published by
   8 *  the Free Software Foundation; either version 2 of the License, or
   9 *  (at your option) any later version.
  10 *
  11 *  This program is distributed in the hope that it will be useful,
  12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 *  GNU General Public License for more details.
  15  ****************************************************************************/
  16 // $Id: rndgen.cxx,v 1.1.1.1 2003/01/04 11:37:22 leo Exp $
  17
  18 /// module description
  19 /// Dr. Park's algorithm published in the Oct. '88 ACM
  20 /// "Random Number Generators: Good Ones Are Hard To Find"
  21 /// His version available at ftp://cs.wm.edu/pub/rngs.tar
  22 /// Present form by many authors.
  23
  24
  25 static int Seed = 1;       /* This is required to be 32 bits long */
  26
  27 //===========================================================================
  28 /// global SetRNG(long)
  29 ///     Set random seed generator,
  30 ///     Given an integer, this routine initializes the RNG seed.
  31 /// tags random_gen
  32 void SetRNG(long s)
  33 {
  34   Seed = (int) s;
  35 }
  36
  37 //===========================================================================
  38 /// global LongRNG()
  39 ///      Returns an pseudo random integer between 0 and 2147483647, inclusive.
  40 /// tags random_gen
  41 long LongRNG()
  42 {
  43   if ((Seed = Seed % 44488 * 48271 - Seed / 44488 * 3399) < 0)
  44     Seed += 2147483647;
  45   return (long) (Seed - 1);
  46 }