Random.h

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#pragma once

#include <chrono>
#include <random>
#include <algorithm>
#include <iterator>
#include <stdlib.h>
#include "common/Thread.h"

namespace ai {

inline std::default_random_engine& randomEngine() {
    AI_THREAD_LOCAL std::default_random_engine engine;
    return engine;
}

inline void randomSeed (unsigned int seed) {
    randomEngine().seed(seed);
}

inline float randomf (float max = 1.0f) {
    std::uniform_real_distribution<float> distribution(0.0, max);
    return distribution(randomEngine());
}

inline int random (int min, int max) {
    std::uniform_int_distribution<int> distribution(min, max);
    return distribution(randomEngine());
}

inline float randomBinomial (float max = 1.0f) {
    return randomf(max) - randomf(max);
}

template<typename I>
inline I randomElement(I begin, I end) {
    const int n = static_cast<int>(std::distance(begin, end));
    std::uniform_int_distribution<> dis(0, n - 1);
    std::advance(begin, dis(randomEngine()));
    return begin;
}

template<typename T>
inline void randomElements(std::vector<T>& vec, int n) {
    if (n >= (int)vec.size()) {
        return;
    }
    std::shuffle(vec.begin(), vec.end(), randomEngine());
    vec.resize(n);
}

template<typename I>
inline void shuffle(I begin, I end) {
    std::shuffle(begin, end, randomEngine());
}

}