mrand.cpp

这是个人脸识别程序

// $common\mrand.cpp 1.5 milbo$
// Warning: this is raw research code -- expect it to be quite messy.
//
// Rand returns an int between 0 and n-1
// RandDouble returns a double between 0 and n-1
// And so on
// These routines are based on "Numerical Recipes in C" 2nd edition ran1().
//
// milbo oct 2002

#include "all.hpp"

static const int N_GENERATORS = 10;
static iGenerator[N_GENERATORS];
static long iRand[N_GENERATORS];

static double Ran1(long *piRand);

//-----------------------------------------------------------------------------

void SeedRand (int iSeed, int iGenerator)
{
ASSERT(iGenerator < N_GENERATORS);

if (iSeed > 0)
	iSeed = -iSeed;	// have to init with a negative number

iRand[iGenerator] = iSeed;
}

//-----------------------------------------------------------------------------
// returns an integer in the range 0 to n-1

int Rand (int n, int iGenerator)
{
ASSERT(iGenerator < N_GENERATORS);

return (int)(n * Ran1(&iRand[iGenerator]));
}

//-----------------------------------------------------------------------------
// returns an integer in the range -n to to n-1

int RandAboutZero (int n, int iGenerator)
{
ASSERT(iGenerator < N_GENERATORS);

return (int)(2 * n * Ran1(&iRand[iGenerator]) - n);
}

//-----------------------------------------------------------------------------
// returns a double random number between 0 to n-EPS

double RandDouble (double n, int iGenerator)
{
ASSERT(iGenerator < N_GENERATORS);

return n * Ran1(&iRand[iGenerator]);
}

//-----------------------------------------------------------------------------
// Returns a gaussian random number with the given standard deviation
//
// We use the fact that the sum of uniformly distibuted random variables
// approximates a gaussian distribution (by the central limit theorem)

double RandGauss (double StdDev, int iGenerator)
{
if (StdDev == 0)	// for efficiency
	return 0;

ASSERT(iGenerator < N_GENERATORS);

double r = 0;
for (int i = 0; i < 12; i++)
	r += RandDouble(2, iGenerator) - 1;		// add a random number between -1 and +1

return (StdDev * r) / 2;
}

//-----------------------------------------------------------------------------
// Return a random number between 0.0 and 1.0 exclustive of the endpoint values
// Lifted from "Numerical Recipes in C" 2nd edition ran1()

#define IA 		16807
#define IM 		2147483647
#define AM 		(1.0/IM)
#define IQ 		127773
#define IR 		2836
#define NTAB 	32
#define NDIV 	(1+(IM-1)/NTAB)
#define EPS 	1.2e-7
#define RNMX 	(1.0-EPS)

static double Ran1 (long *piRand)
{
int j;
long k;
static long iy=0;
static long iv[NTAB];
double temp;

if (*piRand <= 0 || !iy)
	{
	if (-*piRand < 1)
		*piRand=1;
	else
		*piRand = -*piRand;
	for (j=NTAB+7;j>=0;j--)
		{
		k=*piRand/IQ;
		*piRand=IA*(*piRand-k*IQ)-IR*k;
		if (*piRand < 0)
			*piRand += IM;
		if (j < NTAB)
			iv[j] = *piRand;
		}
	iy=iv[0];
	}
k=*piRand/IQ;
*piRand=IA*(*piRand-k*IQ)-IR*k;
if (*piRand < 0)
	*piRand += IM;
j=iy/NDIV;
iy=iv[j];
iv[j] = *piRand;

if ((temp=(AM*iy)) > RNMX)
	return RNMX;
else
	return temp;
}