discrete_distribution.hh

#ifndef LOCARNA_DISCRETE_DISTRIBUTION
#define LOCARNA_DISCRETE_DISTRIBUTION
 
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
 
namespace LocARNA {
 
    // ------------------------------------------------------------
    class DiscreteDistribution {
    private:
        std::vector<double> distrib_acc_;
 
    public:
        explicit
        DiscreteDistribution(const std::vector<double> &distvec) {
            if (distvec.size() == 0)
                return;
 
            distrib_acc_.resize(distvec.size());
 
            distrib_acc_[0] = distvec[0];
            for (size_t i = 1; i < distvec.size(); i++) {
                distrib_acc_[i] += distrib_acc_[i - 1] + distvec[i];
            }
            double max_acc = distrib_acc_[distvec.size() - 1];
            for (size_t i = 0; i < distvec.size(); i++) {
                distrib_acc_[i] /= max_acc;
            }
        }
 
        size_t
        operator()(size_t x) {
            double y = x / (double)RAND_MAX;
 
            size_t i = 0;
            for (; i < distrib_acc_.size() && y > distrib_acc_[i]; ++i)
                ;
 
            assert(i <= distrib_acc_.size());
            return i;
        }
    };
 
} // end namespace LocARNA
 
#endif // LOCARNA_DISCRETE_DISTRIBUTION