libs/libvtrutil/src/vtr_random.h

#ifndef VTR_RANDOM_H
#define VTR_RANDOM_H
#include <algorithm> //For std::swap

namespace vtr {
/*********************** Portable random number generators *******************/
typedef unsigned RandState;

void srandom(int seed);
RandState get_random_state();
int irand(int imax);
int irand(int imax, RandState& rand_state);
float frand();

//Portable/invariant version of std::shuffle
//
//Note that std::shuffle relies on std::uniform_int_distribution
//which can produce different sequences accross different
//compilers/compiler versions.
//
//This version should be deterministic/invariant. However,  since
//it uses vtr::irand(), may not be as well distributed as std::shuffle.
template<typename Iter>
void shuffle(Iter first, Iter last, RandState& rand_state) {
    for (auto i = (last - first) - 1; i > 0; --i) {
        using std::swap;
        swap(first[i], first[irand(i, rand_state)]);
    }
}

} // namespace vtr
#endif