simulation-code-sample/CarSharingSimulation.hpp at main · RyanMcCleary/simulation-code-sample · GitHub

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#ifndef CAR_SHARING_SIMULATION_HPP_INCLUDED
#define CAR_SHARING_SIMULATION_HPP_INCLUDED

#include <cstdint>
#include <random>

using std::uint32_t;
using std::discrete_distribution;

class CarSharingSimulation {

public:

    CarSharingSimulation(
        uint32_t num_stations,        // number of stations in the system
        uint32_t cars_per_station,    // initial cars per station
        uint32_t spaces_per_station,  // number of parking spaces per station
        double prob_class_1,          // the probability that a user makes a single (as opposed to double) reservation
        double lam,                   // combined rate of reservations
        double nu,                    // pickup rate
        double mu                     // dropoff rate
    );

    // run the simulation repeatedly, averaging results
    std::vector<double> repeated_runs(uint32_t num_runs, double end_time, double dt, uint32_t column);

private:

    // transitions of the underlying markov process
    enum class Transition {
        CLASS1_RESERVATION = 0,
        CLASS2_RESERVATION = 1,
        CLASS1_PICKUP = 2,
        CLASS2_PICKUP = 3,
        CLASS1_DROPOFF = 4,
        CLASS2_DROPOFF = 5
    };

    const uint32_t num_stations, cars_per_station, spaces_per_station;
    const double prob_class_1, lam, nu, mu;

    std::vector<uint32_t>
        class1_reservations,
        class1_driving,
        class1_waiting,
        available_cars,
        class2_driving,
        unavailable_spaces,
        _class2_reservations;

    uint32_t &class2_reservations(uint32_t start_station, uint32_t dest_station) {
        return _class2_reservations.at(start_station * num_stations + dest_station);
    }

    std::vector<double> cumulative_stats, stats, cumulative_times, transition_times;

    uint32_t num_reservations_1, num_reservations_2, // number of Class 1 and Class 2 reservations, resp.
        num_driving_1, num_driving_2, // number of Class 1 and Class 2 users driving, resp.
        num_waiting, // class 1 users waiting
        num_stats;  // number of records logged on the current run

    std::mt19937 rng;

    discrete_distribution<uint32_t> class2_reservation_distribution() const {
        discrete_distribution<uint32_t> result(_class2_reservations.cbegin(),
                                     _class2_reservations.cend());
        return result;
    }

    discrete_distribution<uint32_t> class1_reservation_distribution() const {
        discrete_distribution<uint32_t> result(class1_reservations.cbegin(),
                                     class1_reservations.cend());
        return result;
    }

    discrete_distribution<uint32_t> class2_driving_distribution() const {
        discrete_distribution<uint32_t> result(class2_driving.cbegin(),
                                     class2_driving.cend());
        return result;
    }

    discrete_distribution<uint32_t> class1_driving_distribution() const {
        discrete_distribution<uint32_t> result(class1_driving.cbegin() + num_stations,
                                     class1_driving.cend());
        return result;
    }

    uint32_t uniform_random_station();

    bool reservation_update_1();
    bool reservation_update_2();
    void pickup_update_1();
    void pickup_update_2();
    void dropoff_update_1();
    void dropoff_update_2();
    Transition next_transition();
    double next_holding_time();
    void push_time_and_column(double t, uint32_t column);
    void run(double end_time, uint32_t column);
    void average(double end_time, double dt);
    void reset_state();
};

std::vector<double> repeated_runs(
    uint32_t num_stations,
    uint32_t cars_per_station,
    uint32_t spaces_per_station,
    double prob_class_1,
    double lam,
    double nu,
    double mu,
    double end_time,
    double dt);

#endif