/*  Nucleotide Sequence Generator - seq-gen, version 1.2.5 */
/*  (c) Copyright 1996-2001, Andrew Rambaut & Nick Grassly */
/*  Department of Zoology, University of Oxford            */

/******************************************************************************
 
   The following code comes from tools.c in Yang's PAML package

   U(0,1): AS 183: Appl. Stat. 31:188-190 
   Wichmann BA & Hill ID.  1982.  An efficient and portable
   pseudo-random number generator.  Appl. Stat. 31:188-190

   x, y, z are any numbers in the range 1-30000.  Integer operation up
   to 30323 required.
 	
******************************************************************************/

#include <stdio.h>
#include <math.h>
#include "random.h"

static int z_rndu=137;
static unsigned w_rndu=13757;

void SetSeed (int seed)
{
   z_rndu = 170*(seed%178) + 137;
   w_rndu=seed;
}


#ifdef FAST_RANDOM_NUMBER

double rndu (void)
{
   w_rndu *= 127773;
   return ldexp((double)w_rndu, -32);
}

#else 

double rndu (void)
{
   static int x_rndu=11, y_rndu=23;
   double r;

   x_rndu = 171*(x_rndu%177) -  2*(x_rndu/177);
   y_rndu = 172*(y_rndu%176) - 35*(y_rndu/176);
   z_rndu = 170*(z_rndu%178) - 63*(z_rndu/178);
   if (x_rndu<0) x_rndu+=30269;
   if (y_rndu<0) y_rndu+=30307;
   if (z_rndu<0) z_rndu+=30323;
   r = x_rndu/30269.0 + y_rndu/30307.0 + z_rndu/30323.0;
   return (r-(int)r);
}

#endif