random.cpp

来自「一个语言识别引擎」· C++ 代码 · 共 82 行

// -*- mode:C++; tab-width:4; c-basic-offset:4; indent-tabs-mode:nil -*-


#include <yarp/os/Random.h>

#include <math.h>
#include <ace/OS.h>
#include <stdlib.h>

using namespace yarp::os;

double Random::uniform() {
    return double (ACE_OS::rand ()) / double (RAND_MAX);
}


//
// normal distribution random number generator.
// - it might be slow, the standard rand() is used as source.
// - beware of initializing the seed of rand.

// original code copyright reported below.
// summary --
//   CopyPolicy: Preserve copyright notice
//   Copyright: 1994, Everett F. Carter Jr.

/* boxmuller.c           
   Implements the Polar form of the Box-Muller
   Transformation

   (c) Copyright 1994, Everett F. Carter Jr.
   Permission is granted by the author to use
   this software for any application provided this
   copyright notice is preserved.

*/



double Random::normal(double m, double s)	
{				        
    double x1, x2, w, y1;
    static double y2;
    static int use_last = 0;

    if (use_last)		        /* use value from previous call */
		{
			y1 = y2;
			use_last = 0;
		}
    else
		{
			do {
				x1 = 2.0 * uniform() - 1.0;
				x2 = 2.0 * uniform() - 1.0;
				w = x1 * x1 + x2 * x2;
			} while ( w >= 1.0 );

			w = sqrt( (-2.0 * log( w ) ) / w );
			y1 = x1 * w;
			y2 = x2 * w;
			use_last = 1;
		}

    return( m + y1 * s );
}

void Random::seed(int seed) { 
    ACE_OS::srand (seed); 
}


int Random::uniform(int min, int max) {
	int ret = int ((double (ACE_OS::rand()) / double (RAND_MAX)) * (max - min + 1) + min);
    
	// there's a small chance the value is = max+1
	if (ret <= max)
		return ret;
	else
		return max;
}