hydrorandomsed.c

/*-------------------------------------------------------------------------------------------
 *  HydroRandomsed.c
 *
 *	Author: Albert Kettner, March 2006
 *
 *  Generates a large array of normally distributed deviates with zero mean and unit variance.
 *	Other routines sequentially pluck numbers from this array. The numbers are stored in ranarray,
 *	and indexed by nran.
 *  This enables the program to generate all the random numbers it needs (for a year) at once.
 *
 *  Variable	Def.Location	Type	Units	Usage
 *  --------	------------	----	-----	-----
 *  dumlong	HydroRandom.c	long	-	random number generator variable
 *  err		various		int	-	error flag, halts program
 *  fac		HydroRandom.c	float	-	random number generator variable
 *  ii		various		int	-	temporary loop counter
 *  jj		various		int	-	temporary loop counter
 *  rmin	HydroRandom.c	double  -	random number generator stats
 *  rmax	HydroRandom.c	double  -	random number generator stats
 *  rsum	HydroRandom.c	double  -	random number generator stats
 *  rsq		HydroRandom.c	float	-	random number generator variable	
 *  unival[]	HydroRandom.c	float	-	random number generator variable
 *  v1		HydroRandom.c	float	-	random number generator variable
 *  v2		HydroRandom.c	float	-	random number generator variable
 *
 *-------------------------------------------------------------------------------------------*/

#include <math.h>
#include <stdio.h>
#include "hydroinout.h"
#include "hydroparams.h"
#include "hydroalloc_mem.h"
#include "hydrofree_mem.h"
#include "hydrornseeds.h"

/*------------------------
 *  Start of HydroRandomsed
 *------------------------*/
int
hydrorandomsed ()
{

/*-------------------
 *  Local Variables
 *-------------------*/
  float hydroran2sed (long *idum);
  float fac, rsq, v1, v2, *unival;
  double rsum;
  int err, ii, jj;
  err = 0;

/*--------------------------
 *  Reset the nran counter
 *--------------------------*/
  nransediment = 0;
/*
 *  First generate a set of uniform random numbers in [0.0, 1.0].
 *  ran2 is from "Numerical Recipes in C", p282, 2nd ed.
 *  For the first deviate, use rnseed as the seed, making sure that
 *  it is negative, this initializes ran2 appropriately.
 *  For subsequent years, use the generated seed; dumlong should not
 *  be altered between successive deviates in a sequence.
 */
  if (yr == syear[ep])
    {
      rnseed = -INIT_RAN_NUM_SEED - 10 * ep;
    }
  unival = malloc1d (2 * nyears[ep], float);
  for (ii = 0; ii < 2 * nyears[ep]; ii++)
    {
      unival[ii] = hydroran2sed (&rnseed);
    }

/*
 *  Next generate Gaussian distributed deviates.
 *  The routine returns two random numbers for each pass,
 *  so loop through the array at a step of 2.
 *  GASDEV, From "Numerical Recipes in C", p.289, 2nd ed.
 */
  jj = 0;
  for (ii = 0; ii < nyears[ep] - 1; ii += 2)
    {
      do
        {
          v1 = 2.0 * unival[jj] - 1.0;
          v2 = 2.0 * unival[jj + 1] - 1.0;
          rsq = sq (v1) + sq (v2);
          jj += 2;
        }
      while (rsq >= 1.0 || rsq == 0.0);
      fac = sqrt (-2.0 * log (rsq) / rsq);
      ranarraysediment[ii] = (double) v1 *fac;
      ranarraysediment[ii + 1] = (double) v2 *fac;
    }

/*-------------------
 *  Check the stats
 *-------------------*/
  rmin = 0;
  rmax = 0;
  rsum = 0;
  for (ii = 0; ii < nyears[ep] - 1; ii += 2)
    {
      rmin = mn (rmin, ranarraysediment[ii]);
      rmax = mx (rmax, ranarraysediment[ii]);
      rsum += ranarraysediment[ii];
    }
  freematrix1D ((void *) unival);
  return (err);
}                               /* end of HydroRandomsediment */