#include <stdlib.h>
#include <stdio.h>
/*#include <math.h>
*/
#define NPATCHES	20
#define	MAXSTEPS	100
#define	RR		0.1
#define	KK		10.0
#define	DELT		1.0

double rr, kk;
double patch[NPATCHES];

void OutputInsects(int, int);
void ReproduceInsects(int);
double NewPop(double);
void MoveInsects(int);

int main(void)
{
	int t, ipat, seed;

	seed = 1456739853;
	srand48(seed);

	rr = RR*DELT;
	kk = KK;
	for(ipat=0;ipat<NPATCHES;ipat++)
		patch[ipat] = kk;

	for(t=0;t<MAXSTEPS;t++)
	{
		OutputInsects(t,t%2);
		ReproduceInsects(t%2);
		MoveInsects(t%2);
	}
	return (0);
}

void OutputInsects(int time, int ilat)
{
	int ipat;

	if(ilat==0)
	{
		printf("%4d ",time);
		for(ipat=0;ipat<16;ipat+=2)
			printf("%8.4f ",patch[ipat]);
		printf("\n");
	}
}

void ReproduceInsects(int ilat)
{
	int ipat;

	for(ipat=ilat;ipat<NPATCHES;ipat+=2)
	{
		patch[ipat] = NewPop(patch[ipat]);
	}
}

double NewPop(double pop)
{
	double newpop;

	newpop = pop + rr*pop*(1.0-pop/kk);
	if(newpop<0.0) newpop = 0.0;
	return(newpop);
}

void MoveInsects(int ilat)
{
	int ipat;
	double qq;

	for(ipat=1-ilat;ipat<NPATCHES;ipat+=2)
		patch[ipat] = 0.0;

	if(ilat==0)
	{
		qq = drand48();
		patch[NPATCHES-1] += patch[0]*qq;
		patch[1]          += patch[0]*(1.0-qq);
	}
	for(ipat=2-ilat;ipat<NPATCHES-1;ipat+=2)
	{
		qq = drand48();
		patch[ipat-1] += patch[ipat]*qq;
		patch[ipat+1] += patch[ipat]*(1.0-qq);
	}
	if(ilat==1)
	{
		qq = drand48();
		patch[NPATCHES-2] += patch[NPATCHES-1]*qq;
		patch[0]          += patch[NPATCHES-1]*(1.0-qq);
	}
}