Clementine-audio-player-Mac.../3rdparty/libprojectm/RandomNumberGenerators.hpp

123 lines
2.8 KiB
C++

#ifndef RANDOM_NUMBER_GENERATORS_HPP
#define RANDOM_NUMBER_GENERATORS_HPP
#include <cmath>
#include <vector>
#include <cassert>
#include <iostream>
#define WEIGHTED_RANDOM_DEBUG 0
namespace RandomNumberGenerators {
inline float uniform()
/* Uniform random number generator x(n+1)= a*x(n) mod c
with a = pow(7,5) and c = pow(2,31)-1.
Copyright (c) Tao Pang 1997. */
{
const int ia=16807,ic=2147483647,iq=127773,ir=2836;
int il,ih,it;
float rc;
static int iseed = rand();
ih = iseed/iq;
il = iseed%iq;
it = ia*il-ir*ih;
if (it > 0)
{
iseed = it;
}
else
{
iseed = ic+it;
}
rc = ic;
return iseed/rc;
}
inline float gaussian(float mean, float sigma)
{
float x1, x2, w, y1, y2;
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;
float ret = y1*sigma + mean;
return ret;
}
inline std::size_t uniformInteger(std::size_t upperBound=1) {
/// @bug there was a man entry about how this leads to a lousy uniform
/// @bug distribution in practice. should probably review
assert(upperBound > 0);
return ((rand()) % ((int)upperBound));
}
/// Randomizes from probabilistically weighted distribution. Thus,
/// sum of passed in weights should be 1.0
inline std::size_t weightedRandomNormalized(std::vector<float> weights) {
// Choose a random bounded mass between 0 and 1
float cutoff = ((float)(rand())) / (float)RAND_MAX;
//std::cout << "cutoff : " << cutoff << std::endl;
// Sum up mass, stopping when cutoff is reached. This is the typical
// weighted sampling algorithm.
float mass = 0;
for (std::size_t i = 0; i< weights.size() ; i++) {
mass += weights[i];
//std::cout << "mass: " << mass << std::endl;
if (mass >= cutoff)
return i;
}
// Just in case something slips through the cracks
return weights.size()-1;
}
inline std::size_t weightedRandom(const std::vector<int> & weights, unsigned int weightTotalHint = 0) {
if (weightTotalHint == 0) {
for (std::size_t i = 0; i < weights.size();i++)
weightTotalHint += weights[i];
}
const int sampledSum = uniformInteger(weightTotalHint);
int sum = 0;
if (WEIGHTED_RANDOM_DEBUG) std::cout << "[RNG::weightedRandom()] weightTotal = " << weightTotalHint <<
std::endl;
for (std::size_t i = 0; i < weights.size();i++) {
if (WEIGHTED_RANDOM_DEBUG)
std::cout << "[RNG::weightedRandom()] weight[" << i << "] = " << weights[i] <<
std::endl;
sum += weights[i];
if (sampledSum <= sum) {
if (WEIGHTED_RANDOM_DEBUG)
std::cout << "[RNG::weightedRandom()] sampled index " << i << "(" <<
"running sum = " << sum << ", sampled sum = " << sampledSum << std::endl;
return i;
}
}
return weights.size()-1;
}
}
#endif