random.h

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 * Software License Agreement (BSD License)
 *
 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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#ifndef FLANN_RANDOM_H
#define FLANN_RANDOM_H
 
#include <algorithm>
#include <random>
#include <cstdlib>
#include <cstddef>
#include <vector>
 
#include "FLANN/general.h"
 
namespace flann
{
 
inline void seed_random(unsigned int seed)
{
    srand(seed);
}
 
/*
 * Generates a random double value.
 */
inline double rand_double(double high = 1.0, double low = 0)
{
    return low + ((high-low) * (std::rand() / (RAND_MAX + 1.0)));
}
 
inline int rand_int(int high = RAND_MAX, int low = 0)
{
    return low + (int) ( double(high-low) * (std::rand() / (RAND_MAX + 1.0)));
}
 
 
class RandomGenerator
{
public:
    ptrdiff_t operator() (ptrdiff_t i) { return rand_int(i); }
};
 
 
class UniqueRandom
{
    std::vector<int> vals_;
    int size_;
    int counter_;
 
public:
    UniqueRandom(int n)
    {
        init(n);
    }
 
    void init(int n)
    {
        // create and initialize an array of size n
        vals_.resize(n);
        size_ = n;
        for (int i = 0; i < size_; ++i) vals_[i] = i;
 
        // shuffle the elements in the array
        std::random_device rd;   // non-deterministic generator
        std::mt19937 gen(rd());  // to seed mersenne twister.
        std::shuffle(vals_.begin(), vals_.end(), rd);
 
        counter_ = 0;
    }
 
    int next()
    {
        if (counter_ == size_) {
            return -1;
        }
        else {
            return vals_[counter_++];
        }
    }
};
 
}
 
#endif //FLANN_RANDOM_H