Re: ran3 random num generator

On May 5, 6:40 am, "osmium" <r124c4u...@[EMAIL PROTECTED]
> wrote:
> <nko...@[EMAIL PROTECTED]
> wrote:
> >> Does anyone know where I can find a version of the ran3 random number
> >> generator for C++ that will play nice on windows as a console app,
> >> preferably something you can call simply with random1 =ran3() or
> >> something similar.
>
> >> All the versions I found so far are implemented in different
languages
> >> or for some reason only work with Linux.
>
> >> Thanks
>
> > Sorry, I forgot to mention that the ran3 generator algorithm is the
> > one mentioned in the book Numerical recipes.
>
> How about this?
>
> http://www.cs.utah.edu/~tch/cl*****/cs4550/code/Numerical-Recipes/sou...
>
> I changed the call to this:
>
>   float ran3(int* idum)
>   //int *idum;
>
>  and it seemed to work.  Tested with DevC (in C++ mode) on a Windows
console
> application.



Any mistakes below? Am I right in guessing that I have to feed a seed
value when I call ran3 because it doesn't generate its own? If so how
would I set up the seed to generate a sequence of 'random' numbers in
a loop?



 #include <iostream> // for std::cout
#include <fstream>
#include <iomanip>
#include <stdlib.h>
#include <cstdio>
#include <time.h>
#include <math.h>
using namespace std;
#define MBIG 1000000000
#define MSEED 161803398
#define MZ 0
#define FAC (1.0/MBIG)
float ran3(int *) ;




float ran3(int* idum)
//int *idum;
{
	static int inext,inextp;
	static long ma[56];
	static int iff=0;
	long mj,mk;
	int i,ii,k;

	if (*idum < 0 || iff == 0) {
		iff=1;
		mj=MSEED-(*idum < 0 ? -*idum : *idum);
		mj %= MBIG;
		ma[55]=mj;
		mk=1;
		for (i=1;i<=54;i++) {
			ii=(21*i) % 55;
			ma[ii]=mk;
			mk=mj-mk;
			if (mk < MZ) mk += MBIG;
			mj=ma[ii];
		}
		for (k=1;k<=4;k++)
			for (i=1;i<=55;i++) {
				ma[i] -= ma[1+(i+30) % 55];
				if (ma[i] < MZ) ma[i] += MBIG;
			}
		inext=0;
		inextp=31;
		*idum=1;
	}
	if (++inext == 56) inext=1;
	if (++inextp == 56) inextp=1;
	mj=ma[inext]-ma[inextp];
	if (mj < MZ) mj += MBIG;
	ma[inext]=mj;
	return mj*FAC;
}

#undef MBIG
#undef MSEED
#undef MZ
#undef FAC






int main()
{
double random;

int seed =2;



random =ran3(&seed);

cout << random << endl;

return 0;

}