src/LocARNA/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