// -*- C++ -*-
// $RCSfile: random.C,v $
// $Revision: 1.6 $
// $Author: langer $
// $Date: 2000/11/01 16:41:11 $


/* This software was produced by NIST, an agency of the U.S. government,
 * and by statute is not subject to copyright in the United States.
 * Recipients of this software assume all responsibilities associated
 * with its operation, modification and maintenance. However, to
 * facilitate maintenance we ask that before distributing modifed
 * versions of this software, you first contact the authors at
 * oof_manager@ctcms.nist.gov. 
 */


// random number generator.

// currently just a shell for the IRIX random().

#include "charstring.h"
#include "random.h"
#include <math.h>
#include "stdlib.h"

static const long BIGGEST = 2147483647; // 2^31-1

void rndmseed(int seed) {
  srandom(seed);
}

double rndm() {
  return random()/(BIGGEST+1.0);
}

void setseed(const CharString&) { // called from menus
  rndmseed(seed);
}

// gaussian deviates, copied from numerical recipes

double gasdev() {
  static int saved = 0;
  static double save_me;
  double v1, v2, rsq;
  if(!saved) {
    do {
      v1 = 2.0*rndm() - 1.0;
      v2 = 2.0*rndm() - 1.0;
      rsq = v1*v1 + v2*v2;
    } while(rsq >= 1.0 || rsq == 0);
	
    double fac = sqrt(-2.0*log(rsq)/rsq);
    save_me = v1*fac;
    saved = 1;
    return v2*fac;
  }
  else {
    saved = 0;
    return save_me;
  }
}