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Airport.cpp
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Airport.cpp
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#include <iostream>
#include <cmath>
#include <time.h>
#include <climits>
#define max_int __INT32_MAX__
using namespace std;
const int plane_limit = 10000;
enum Error_code {success, overflow, underflow, fail};
enum Plane_status {null, arriving, departing};
class Plane
{
public:
Plane();
Plane(int fit, int time, Plane_status status);
void refuse() const;
void land(int time) const;
void fly(int time) const;
int started() const;
private:
int fit_num;
int clock_start;
Plane_status state;
};
class Extended_queue
{
public:
Extended_queue();
void serve();
Error_code append(const Plane &item);
void retrieve(Plane &item);
bool empty() const;
void clear();
bool full() const;
int size() const;
private:
int count;
int index;
int rear;
Plane entry[plane_limit];
};
enum Runway_activity {idle, land, takingoff};
class Runway
{
public:
Runway(int limit);
Error_code can_land(const Plane ¤t);
Error_code can_depart(const Plane ¤t);
Runway_activity activity(int time, Plane &moving);
void shut_down(int time) const;
private:
Extended_queue landing;
Extended_queue takeoff;
int queue_limit;
int num_land_requests;
int num_takeoff_requests;
int num_landings;
int num_takeoffs;
int num_land_accepted;
int num_takeoff_accepted;
int num_land_refused;
int num_takeoff_refused;
int land_wait;
int takeoff_wait;
int idle_time;
};
class Random
{
public:
Random(bool pseudo = true);
int poisson(double mean);
double random_real();
private:
int reseed();
int seed, multiplier, add_on;
};
void initialize(int &end_time, int &queue_limit, double &arrival_rate, double &departure_rate)
{
cout << "This program simulates an airport with only one runway" << endl << "One plane can land or depart in each unit of time" << endl;
cout << "Up to what number of planes can be waiting to land" << " or take off at any time?" << flush;
cin >> queue_limit;
cout << "How many units of time will the simulation run?" << flush;
cin >> end_time;
bool acceptable;
do
{
cout << "Expected number of arrivals per unit time?" << flush;
cin >> arrival_rate;
cout << "Expected number of departures per unit time?" << flush;
cin >> departure_rate;
if (arrival_rate < 0.0 || departure_rate < 0.0)
cerr << "These rates must be nonnegative" << endl;
else
acceptable = true;
if (acceptable && arrival_rate + departure_rate > 1.0)
cerr << "Safety Warning: This airport will become saturated" << endl;
} while (!acceptable);
}
void run_idle(int time)
{
cout << time << ": Runway is idle" << endl;
}
int main()
{
int end_time;
int queue_limit;
int flight_number = 0;
double arrival_rate, departure_rate;
initialize(end_time, queue_limit, arrival_rate, departure_rate);
Random variable;
Runway small_airport(queue_limit);
for (int current_time = 0; current_time < end_time; current_time++)
{
int number_arrivals = variable.poisson(arrival_rate);
for (int i = 0; i < number_arrivals; i++)
{
Plane current_plane(flight_number++, current_time, arriving);
if (small_airport.can_land(current_plane) != success)
current_plane.refuse();
}
int number_departures = variable.poisson(departure_rate);
for (int j = 0; j < number_departures; j++)
{
Plane current_plane(flight_number++, current_time, departing);
if (small_airport.can_depart(current_plane) != success)
current_plane.refuse();
}
Plane moving_plane;
switch (small_airport.activity(current_time, moving_plane))
{
case land:
moving_plane.land(current_time);
break;
case takingoff:
moving_plane.fly(current_time);
break;
case idle:
run_idle(current_time);
}
}
small_airport.shut_down(end_time);
return 0;
}
Extended_queue::Extended_queue()
{
index = 0;
count = 0;
rear = plane_limit - 1;
}
Error_code Extended_queue::append(const Plane &item)
{
if (count >= plane_limit) return overflow;
count++;
rear = ((rear + 1) == plane_limit)?0:(rear+1);
entry[rear] = item;
return success;
}
void Extended_queue::serve()
{
count--;
index = ((index + 1) == plane_limit)?0:(index + 1);
}
void Extended_queue::retrieve(Plane &item)
{
item = entry[index];
}
bool Extended_queue::empty() const
{
return count == 0;
}
void Extended_queue::clear()
{
index = count = 0;
}
bool Extended_queue::full() const
{
return count == plane_limit;
}
int Extended_queue::size() const
{
return count;
}
// Runway init
Runway::Runway(int limit)
{
queue_limit = limit;
num_land_requests = num_takeoff_requests = 0;
num_landings = num_takeoffs = 0;
num_land_refused = num_takeoff_refused = 0;
num_land_accepted = num_takeoff_accepted = 0;
land_wait = takeoff_wait = idle_time = 0;
}
// accept plane to runway
Error_code Runway::can_land(const Plane ¤t)
{
Error_code result;
if (landing.size() < queue_limit)
result = landing.append(current);
else
result = fail;
num_land_requests++;
if (result != success)
num_land_refused++;
else
num_land_accepted++;
return result;
}
Error_code Runway::can_depart(const Plane ¤t)
{
Error_code result;
if (takeoff.size() < queue_limit)
result = takeoff.append(current);
else
result = fail;
num_takeoff_requests++;
if (result != success)
num_takeoff_refused++;
else
num_takeoff_accepted++;
return result;
}
Runway_activity Runway::activity(int time, Plane &moving)
{
Runway_activity in_progress;
if (!landing.empty()) {
landing.retrieve(moving);
land_wait += time - moving.started();
num_landings++;
in_progress = land;
landing.serve();
}
else if (!takeoff.empty()) {
takeoff.retrieve(moving);
takeoff_wait += time - moving.started();
num_takeoffs++;
in_progress = takingoff;
takeoff.serve();
}
else {
idle_time++;
in_progress = idle;
}
return in_progress;
}
void Runway::shut_down(int time) const
{
cout << "Simulation has concluded after " << time << " time units" << endl << "Total number of planes processed " << (num_land_requests + num_takeoff_requests) << endl << "Total number of planes asking to land " << num_land_requests << endl << "Total number of planes asking to take off " << num_takeoff_requests << endl << "Total number of planes accepted for landing " << num_land_accepted << endl << "Total number of planes accepted for takeoff " << num_takeoff_accepted << endl << "Total number of planes refused for landing " << num_land_refused << endl << "Total number of planes refused for takeoff " << num_takeoff_refused << endl << "Total number of planes that landed " << num_landings << endl << "Total number of planes that took off " << num_takeoffs << endl << "Total number of planes left in landing queue " << landing.size( ) << endl << "Total number of planes left in takeoff queue " << takeoff.size( ) << endl;
cout << "Percentage of time runway idle " << 100.0 * ((float) idle_time)/((float) time) << "%" << endl;
cout << "Average wait in landing queue " << ((float) land_wait)/((float) num_landings) << " time units";
cout << endl << "Average wait in takeoff queue " << ((float) takeoff_wait)/((float) num_takeoffs) << " time units" << endl;
cout << "Average observed rate of planes wanting to land " << ((float) num_land_requests)/((float) time) << " per time unit" << endl;
cout << "Average observed rate of planes wanting to take off " << ((float) num_takeoff_requests)/((float) time) << " per time unit" << endl;
}
Plane::Plane(int fit, int time, Plane_status status)
{
fit_num = fit;
clock_start = time;
state = status;
cout << "Plane number " << fit << " ready to ";
if (status == arriving)
cout << "land" << endl;
else
cout << "take off" << endl;
}
Plane::Plane()
{
fit_num = -1;
clock_start = -1;
state = null;
}
void Plane::refuse() const
{
cout << "Plane number " << fit_num;
if (state == arriving)
cout << " directed to another airport" << endl;
else
cout << " told to try to takeoff again later" << endl;
}
void Plane::land(int time) const
{
int wait = time - clock_start;
cout << time << ": Plane number " << fit_num << " landed after " << wait << " time unit" << ((wait == 1)? "":"s") << " in the takeoff queue" << endl;
}
void Plane::fly(int time) const
{
int wait = time - clock_start;
cout << time << ": Plane number " << fit_num << " took off after " << wait << " time unit" << ((wait == 1)? "":"s") << " in the takeoff queue" << endl;
}
int Plane::started() const
{
return clock_start;
}
Random::Random(bool pseudo)
{
if (pseudo) seed = 1;
else seed = time(NULL) % max_int;
multiplier = 2743;
add_on = 5923;
}
int Random::reseed()
{
seed = seed * multiplier + add_on;
return seed;
}
double Random::random_real()
{
double max = max_int + 1.0;
double temp = reseed();
if (temp < 0) temp = temp + max;
return temp/max;
}
int Random::poisson(double mean)
{
double limit = exp(-mean);
double product = random_real();
int count = 0;
while (product > limit) {
count++;
product *= random_real();
}
return count;
}