# Question & Answer: As mentioned in class, there are usually two ways in which customers are lined up for access to a number of service…..

As mentioned in class, there are usually two ways in which customers are lined up for access to a number of service windows. Typically in a bank, there is one queue line for everyone and a number of windows. When a window becomes free, the next person at the head of the queue leaves the queue and proceeds to the window. People coming into the bank simply join the single queue at the tail of the queue. At Tim’s in Geology, we have the other approach to providing service. Every service window has its own queue. Typically when a person comes up to the lines, they choose the shortest line to join and then stay in that line. It can frustrate some people to see the longer line actually move faster and sometimes people will line hop (i.e. when the other line is shorter than the queue in front of me) So which is the best approach? In this assignment we are going to try and determine that. Here are the parameters for the simulation. For both simulations you are to do the following Run the simulation for 6 hours A new customer group arrives every 1 minute t 58 seconds (i.e. as little as 2 seconds apart and as much as 1 min 50 seconds apart A group will consist of 1 to 6 customers following this distribution o 1 person-30% o 2 people -40% o 3 people 20% o 4 people 5% o 5 people 3% o 6 people 2% Each person in the group joins the queue single file but we can use the same join time for each member of the group Average serving time for a customer is 2 minutes t 65 seconds. For each simulation below, report on the following: Maximum number of customers served Average number of customers served per window per hour Average wait time in the queue for each customer Maximum wait time in the queue Average queue length for each queue Maximum queue length for each queue Simulation #1 Simulate a scenario with two server windows and two queues. When a group of customers arrive each individual in the group will choose the same queue, but the first individual will choose the shortest queue.

import java.util.Random;

//old one had one lineup for each of 2 windows, we are just going to have one big line up now
public class driver {

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Question & Answer: As mentioned in class, there are usually two ways in which customers are lined up for access to a number of service…..
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public static final double SIM_TIME = 21600;
public static final int SECONDS_PER_HOUR = 3600;

public static double currentTime, totalWaitTime, maxWaitTime, queue1LengthTime, lastTime = 0;
public static EventQueue queue;
public static CustomerQueue lineup1;
public static boolean window1IsIdle, window2IsIdle, window3IsIdle, window4IsIdle;
public static int customersServed, nextCustomerNumber, maxQueueLength = 0;

public static void scheduleNextCustomerGroup(double time){

Random generator = new Random();

double number = 100*generator.nextDouble();

if (number <= 30){
custGroupJoinQ e = new custGroupJoinQ(time, 1);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());
}//1 customer
else if (number <= 70){

custGroupJoinQ e = new custGroupJoinQ(time,2);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}//2 customer
else if (number <= 90){

custGroupJoinQ e = new custGroupJoinQ(time,3);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}//3 customer
else if (number <= 95){
custGroupJoinQ e = new custGroupJoinQ(time,4);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}//4 customer
else if (number <= 98){

custGroupJoinQ e = new custGroupJoinQ(time,5);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}//5 customer
else if (number <= 100){

custGroupJoinQ e = new custGroupJoinQ(time,6);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}//6 customer
}

public static void scheduleNextServiceStart1(double time){
serviceStart1 e = new serviceStart1(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}

public static void scheduleNextServiceStart2(double time){
serviceStart2 e = new serviceStart2(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}
public static void scheduleNextServiceStart3(double time){
serviceStart3 e = new serviceStart3(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}
public static void scheduleNextServiceStart4(double time){
serviceStart4 e = new serviceStart4(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());

}

public static void scheduleNextServiceEnd1(double time){
serviceEnd1 e = new serviceEnd1(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());
}

public static void scheduleNextServiceEnd2(double time){
serviceEnd2 e = new serviceEnd2(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());
}
public static void scheduleNextServiceEnd3(double time){
serviceEnd3 e = new serviceEnd3(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());
}
public static void scheduleNextServiceEnd4(double time){
serviceEnd4 e = new serviceEnd4(time);
queue.Enqueue(e);
System.out.println(currentTime+e.toString());
}

public static void openForBuisiness(){

currentTime = 0;
nextCustomerNumber = 1;
queue = new EventQueue();
lineup1 = new CustomerQueue();
window1IsIdle = true;
window2IsIdle = true;
window3IsIdle = true;
window4IsIdle = true;
scheduleNextCustomerGroup(currentTime + generateArrivalTime());
}

public static void acceptCustomer(double time) {
System.out.println(currentTime + ” there is a customer in lineup1: “+!lineup1.isEmpty());
System.out.println(currentTime + ” window 1 is available: “+window1IsIdle);

System.out.println(currentTime + ” window 2 is available: “+window2IsIdle);
System.out.println(currentTime + ” window 3 is available: “+window3IsIdle);
System.out.println(currentTime + ” window 4 is available: “+window4IsIdle);

if ( (!lineup1.isEmpty()) && window1IsIdle) scheduleNextServiceStart1(time);
else if ( (!lineup1.isEmpty()) && window2IsIdle) scheduleNextServiceStart2(time);
else if ( (!lineup1.isEmpty()) && window3IsIdle) scheduleNextServiceStart3(time);
else if ( (!lineup1.isEmpty()) && window4IsIdle) scheduleNextServiceStart4(time);

}

Customer customer = new Customer(nextCustomerNumber);
nextCustomerNumber++;
customer.setTimeJoinQueue(currentTime);
lineup1.joinQ(customer);
}

public static void removeCustFromFront1(){
}
public static void processEvent(){

Event event;
event = queue.Dequeue();
currentTime = event.scheduledTime;

if (event.eventType == “custGroupJoinQ”) {
for (int i=0; i < ((custGroupJoinQ)event).numberOfCustomers; i++)

scheduleNextCustomerGroup(currentTime + generateArrivalTime());
}

if (event.eventType == “serviceStart1″){
removeCustFromFront1();
System.out.println(currentTime+” EVENT:serviceStart1 – customer removed from lineup1. lineup1 length:”+lineup1.length);

scheduleNextServiceEnd1(currentTime + generateServiceTime());
window1IsIdle = false;
}

if (event.eventType == “serviceStart2″){
removeCustFromFront1();
System.out.println(currentTime+” EVENT:serviceStart2 – customer removed from lineup1. lineup1 length:”+lineup1.length);

scheduleNextServiceEnd2(currentTime + generateServiceTime());
window2IsIdle = false;
}
if (event.eventType == “serviceStart3″){
removeCustFromFront1();
System.out.println(currentTime+” EVENT:serviceStart3 – customer removed from lineup1. lineup1 length:”+lineup1.length);
scheduleNextServiceEnd3(currentTime + generateServiceTime());
window3IsIdle = false;
}

if (event.eventType == “serviceStart4″){
removeCustFromFront1();
System.out.println(currentTime+” EVENT:serviceStart4 – customer removed from lineup1. lineup1 length:”+lineup1.length);
scheduleNextServiceEnd4(currentTime + generateServiceTime());
window4IsIdle = false;
}
if (event.eventType == “serviceEnd1″){
System.out.println(currentTime+” EVENT:serviceEnd1″);

window1IsIdle = true;
}

if (event.eventType == “serviceEnd2″){
System.out.println(currentTime+” EVENT:serviceEnd2″);

window2IsIdle = true;
}
if (event.eventType == “serviceEnd3″){
System.out.println(currentTime+” EVENT:serviceEnd3″);

window3IsIdle = true;
}
if (event.eventType == “serviceEnd4″){
System.out.println(currentTime+” EVENT:serviceEnd4″);

window4IsIdle = true;
}
}

double waitTime;
customer.setTimeToWindow(currentTime – customer.timeJoinedQueue);
waitTime = customer.timeToWindow;
if (waitTime > maxWaitTime) maxWaitTime = waitTime;
if (lineup1.length > maxQueueLength) maxQueueLength = lineup1.length;

totalWaitTime = totalWaitTime + waitTime;
queue1LengthTime = lineup1.length * (currentTime – lastTime) + queue1LengthTime;

lastTime = currentTime;
}

public static void reportStats(){
System.out.println(“average customers served per hour: ” + customersServed / (SIM_TIME/SECONDS_PER_HOUR));
System.out.println(“average wait time in queue for each customer: ” + totalWaitTime/customersServed + ” seconds”);
System.out.println(“the longest any customer had to wait was: ” + maxWaitTime +” seconds”);
System.out.println(“the average queue length was: “+ queue1LengthTime / SIM_TIME);
System.out.println(“the maximum queue length was ” + maxQueueLength);
}

public static double generateArrivalTime(){

Random generator = new Random();
return 10 + Math.abs(100*generator.nextDouble());
}

public static double generateServiceTime(){

Random generator = new Random();
return 55 + Math.abs(130*generator.nextDouble());

}

public static void main(String[] args) {

openForBuisiness();
while (currentTime < SIM_TIME){
System.out.println(currentTime+”process event”);

processEvent();
System.out.println(currentTime+”accept customer”);

acceptCustomer(currentTime);

}

reportStats();
}
}

EventQueue.java

import java.util.Comparator;
import java.util.PriorityQueue;

public class EventQueue {

PriorityQueue<Event> queue;
Comparator<Event> comparator;

public EventQueue(){
comparator = new EventComparator();
queue = new PriorityQueue<Event>(1, comparator);
}

public boolean Enqueue(Event e){
}

public Event Dequeue(){
return queue.poll();
}

public int size(){
return queue.size();
}
}

Event.java

public class Event {

String eventType;
double scheduledTime;

public Event(){
eventType = “”;
scheduledTime=0;
}

public Event(String type, double time) {
eventType = type;
scheduledTime = time;
}

public String toString(){
return eventType+ ” “+ scheduledTime;
}
}

CustomerQueue.java

public class CustomerQueue extends LinkedListForCustQ {

int length, maxLength, totalCustomers;
Customer info;

public CustomerQueue() {
super();
length = 0;
maxLength = 0;
totalCustomers = 0;
info = null;

}

public void joinQ(Customer customer) {
queueJoin(customer);
totalCustomers++;
length++;
if (length > maxLength) maxLength = length;
}

public Customer leaveQ() {
length–;
totalCustomers–;
return queueLeave();
}

}

// this class implements the standard abstract data type linked list as an object
Customer info;
boolean amEmpty;

// interface methods here
// QUEUE interface
public void queueJoin(Customer inInfo) {
// Join(info): info becomes the end of the QUEUE the last item inserted
this.insertInfo(inInfo);
}
public Customer queueLeave() {
// info <– Leave(): if the queue is empty nothing is returned
//                 if the queue is not empty the last item in the list is returned and removed from the queue
if (this.isEmpty()) { return null;}
// if last item in list return and remove else leave from rest of queue
Customer tempCust;
if (this.nextList.isEmpty()) {
tempCust = this.info;
this.deleteInfo(tempCust);
} else {
// get from later in list
tempCust = this.nextList.queueLeave();
}
return tempCust;
}

// end of interface methods

info = null;
nextList = null;
amEmpty = true;
}
public boolean isEmpty() {
return (amEmpty);
}
public void insertInfo(Customer inInfo) {
if (this.amEmpty) {
// insert info here and add a new empty at end
info = inInfo;
nextList = tempLList;
amEmpty = false;
}
else {

this.nextList.insertInfo(this.info);
this.info = inInfo;

}
}
public void deleteInfo(Customer outInfo) {
if (this.amEmpty)
return;

// check if this is the info to delete
if (this.info.customerNumber != outInfo.customerNumber) {
//                System.out.println(“Didn’t match so looking further down list”);
this.nextList.deleteInfo(outInfo);
return;
}
// found it so delete it
if (this.nextList.isEmpty()) {
this.nextList = null;
this.info = null;
amEmpty = true;
//                System.out.println(“Deleting from last element”);
}
else {
this.info = this.nextList.info; // copy next info to current
this.nextList.deleteInfo(this.info);
//                System.out.println(“Shifted info forward and deleting down rest of list”);
}
}
public String traverseList() {
// add current content to list returned by the rest of the list
if (this.isEmpty())
return “”;
if (this.nextList.isEmpty())
return “customer number: “+this.info.customerNumber;
return “customer number: “+this.info.customerNumber+”, “+this.nextList.traverseList();
}
}

Customer.java

public class Customer {

int customerNumber;
double timeJoinedQueue, timeToWindow;

public Customer () {customerNumber = 0; timeJoinedQueue = 0; timeToWindow = 0; }

public Customer (int number) {customerNumber = number; timeJoinedQueue = 0; timeToWindow = 0;}

public void setTimeJoinQueue(double time) {timeJoinedQueue = time;}

public void setTimeToWindow(double time) {timeToWindow = time;}

public double timeInQueue(double currentTime) {return currentTime – timeJoinedQueue;}

public double timeAtWindow(double currentTime) {return currentTime – timeToWindow – timeJoinedQueue;}
}

EventComparator.java

import java.util.Comparator;

public class EventComparator implements Comparator<Event>
{
@Override
public int compare(Event x, Event y)
{

if (x.scheduledTime < y.scheduledTime)
{
return -1;
}
if (x.scheduledTime > y.scheduledTime)
{
return 1;
}
if (x.scheduledTime == y.scheduledTime)//always handle customers joining the queue first
{
if(x.eventType == “custJoinQ”)
{
return 1;
}
else if (y.eventType == “custJoinQ”)
{
return -1;
}
if(x.eventType == “serviceEnd1”)
{
return 1;
}
else if (y.eventType == “serviceEnd1”)
{
return -1;
}
if(x.eventType == “serviceEnd2”)
{
return 1;
}
else if (y.eventType == “serviceEnd2”)
{
return -1;
}
if(x.eventType == “serviceStart1”)
{
return 1;
}
else if (y.eventType == “serviceStart1”)
{
return -1;
}
if(x.eventType == “serviceStart2”)
{
return 1;
}
else if (y.eventType == “serviceStart2”)
{
return -1;
}
}

return 0;
}
}

custGroupJoinQ.java

public class custGroupJoinQ extends Event {
int numberOfCustomers;
public custGroupJoinQ(double time) {
eventType = “custGroupJoinQ”;
scheduledTime = time;
numberOfCustomers =1;
}

public custGroupJoinQ(double time, int numcust) {
eventType = “custGroupJoinQ”;
scheduledTime = time;
numberOfCustomers = numcust;
}
public void generateNext(EventQueue queue, double time){
custGroupJoinQ event = new custGroupJoinQ(time);
queue.Enqueue(event);
return;
}

}

serviceStart1.java

public class serviceStart1 extends Event {

public serviceStart1(double time) {
eventType = “serviceStart1”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceStart1 event = new serviceStart1(time);
queue.Enqueue(event);
return;
}

}

serviceStart2.java

public class serviceStart2 extends Event {

public serviceStart2(double time) {
eventType = “serviceStart2”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceStart2 event = new serviceStart2(time);
queue.Enqueue(event);
return;
}

}

serviceStart3.java

public class serviceStart3 extends Event {

public serviceStart3(double time) {
eventType = “serviceStart3”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceStart3 event = new serviceStart3(time);
queue.Enqueue(event);
return;
}

}

serviceStart4.java

public class serviceStart4 extends Event {

public serviceStart4(double time) {
eventType = “serviceStart4”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceStart4 event = new serviceStart4(time);
queue.Enqueue(event);
return;
}

}

serviceEnd2.java

public class serviceEnd2 extends Event {

public serviceEnd2(double time) {
eventType = “serviceEnd2”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceEnd2 event = new serviceEnd2(time);
queue.Enqueue(event);
return;
}

}

serviceEnd1.java

public class serviceEnd1 extends Event {

public serviceEnd1(double time) {
eventType = “serviceEnd1”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceEnd1 event = new serviceEnd1(time);
queue.Enqueue(event);
return;
}

}

serviceEnd3.java

public class serviceEnd3 extends Event {

public serviceEnd3(double time) {
eventType = “serviceEnd3”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceEnd3 event = new serviceEnd3(time);
queue.Enqueue(event);
return;
}

}

serviceEnd4.java

public class serviceEnd4 extends Event {

public serviceEnd4(double time) {
eventType = “serviceEnd4”;
scheduledTime = time;
}

public void generateNext(EventQueue queue, double time){
serviceEnd4 event = new serviceEnd4(time);
queue.Enqueue(event);
return;
}

}