mirror of
https://github.com/clementine-player/Clementine
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126 lines
2.8 KiB
C++
126 lines
2.8 KiB
C++
#ifndef RANDOM_NUMBER_GENERATORS_HPP
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#define RANDOM_NUMBER_GENERATORS_HPP
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#include <cmath>
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#include <vector>
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#include <cassert>
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#include <iostream>
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#ifdef WIN32
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#include <stdlib.h>
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#endif
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#define WEIGHTED_RANDOM_DEBUG 0
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namespace RandomNumberGenerators {
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inline float uniform()
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/* Uniform random number generator x(n+1)= a*x(n) mod c
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with a = pow(7,5) and c = pow(2,31)-1.
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Copyright (c) Tao Pang 1997. */
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{
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const int ia=16807,ic=2147483647,iq=127773,ir=2836;
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int il,ih,it;
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float rc;
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static int iseed = rand();
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ih = iseed/iq;
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il = iseed%iq;
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it = ia*il-ir*ih;
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if (it > 0)
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{
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iseed = it;
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}
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else
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{
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iseed = ic+it;
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}
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rc = ic;
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return iseed/rc;
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}
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inline float gaussian(float mean, float sigma)
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{
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float x1, x2, w, y1, y2;
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do {
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x1 = 2.0 * uniform() - 1.0;
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x2 = 2.0 * uniform() - 1.0;
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w = x1 * x1 + x2 * x2;
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} while ( w >= 1.0 );
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w = sqrt( (-2.0 * log( w ) ) / w );
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y1 = x1 * w;
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y2 = x2 * w;
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float ret = y1*sigma + mean;
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return ret;
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}
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inline std::size_t uniformInteger(std::size_t upperBound=1) {
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/// @bug there was a man entry about how this leads to a lousy uniform
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/// @bug distribution in practice. should probably review
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assert(upperBound > 0);
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return ((rand()) % ((int)upperBound));
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}
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/// Randomizes from probabilistically weighted distribution. Thus,
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/// sum of passed in weights should be 1.0
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inline std::size_t weightedRandomNormalized(std::vector<float> weights) {
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// Choose a random bounded mass between 0 and 1
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float cutoff = ((float)(rand())) / (float)RAND_MAX;
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//std::cout << "cutoff : " << cutoff << std::endl;
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// Sum up mass, stopping when cutoff is reached. This is the typical
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// weighted sampling algorithm.
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float mass = 0;
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for (std::size_t i = 0; i< weights.size() ; i++) {
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mass += weights[i];
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//std::cout << "mass: " << mass << std::endl;
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if (mass >= cutoff)
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return i;
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}
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// Just in case something slips through the cracks
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return weights.size()-1;
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}
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inline std::size_t weightedRandom(const std::vector<int> & weights, unsigned int weightTotalHint = 0) {
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if (weightTotalHint == 0) {
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for (std::size_t i = 0; i < weights.size();i++)
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weightTotalHint += weights[i];
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}
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const int sampledSum = uniformInteger(weightTotalHint);
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int sum = 0;
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if (WEIGHTED_RANDOM_DEBUG) std::cout << "[RNG::weightedRandom()] weightTotal = " << weightTotalHint <<
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std::endl;
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for (std::size_t i = 0; i < weights.size();i++) {
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if (WEIGHTED_RANDOM_DEBUG)
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std::cout << "[RNG::weightedRandom()] weight[" << i << "] = " << weights[i] <<
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std::endl;
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sum += weights[i];
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if (sampledSum <= sum) {
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if (WEIGHTED_RANDOM_DEBUG)
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std::cout << "[RNG::weightedRandom()] sampled index " << i << "(" <<
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"running sum = " << sum << ", sampled sum = " << sampledSum << std::endl;
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return i;
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}
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}
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return weights.size()-1;
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}
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}
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#endif
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