1 Introduction
Heraclitus once said The only constant in life is change. Heraclitus was a wise man, indeed, but he missed an exception: if you take CMPE 250, you solve a Discrete Event Simulation (DES) project!
Well, but what is DES?
Enter, Wikipedia: A discrete-event simulation (DES) models the operation of a system as a (discrete) sequence of events in time. Each event occurs at a particular instant in time and marks a change of state in the system. Between consecutive events, no change in the system is assumed to occur; thus the simulation time can directly jump to the occurrence time of the next event. In other words, DES is the representation of a certain process by simulating certain events which occur at certain times. Hence, time is not continuous in DES and progress according to the events. As a demonstrative example, a process of taking a coffee can be simulated as follows:
- TIME: 09:00 Go into the checkout queue.
- TIME: 09:05 Order your coffee and make your payment.
- TIME: 09:10 Go into the serving queue.
- TIME: 09:15 Wait for the preparation of your coffee and enjoy your free time.
- TIME: 09:20 Grab your coffee and enjoy!
Note that in DES the only things that count are events and everything else is ignored. In the case of the customer, until 09:20 only 5 things happened. Additionally, the time progressed in a discrete fashion (i.e. jumped from one event to the next one). [1]
In this project, you are expected to simulate training procedure of ExcelFed, which is a tennis club founded by his excellency
2 Details of the ExcelFed
Do you know his excellency? This is not even a question, everyone knows him. Yes, I am talking about Roger Federer[2] who is the best tennis player ever! He has decided to retire since he is not young enough to continue his career. However, he wants to transfer his great experience to the new generation. Thats why, he has founded ExcelFed.
Roger is very experienced so he knows almost everything that plays a huge role in the development of the tennis player. He has already hired great nutritionists and chefs. Additionally, he has a consulting team consists of Rafael Nadal and Novak Djokovic. Furthermore, he has rent nice tennis courts. His aim is to train children in very good conditions so that there are better tennis players.
There is one little problem though. He needs great training coaches, masseurs, and physiotherapists but he does not know how many he needs. He may hire many staffs but this would be a waste of money and there are not many outstanding staffs. Therefore, he decided to simulate the training procedure of ExcelFed with fictional players and staffs to find how many of them would be enough. However, his relationship with simulation tools and coding is terrible so he needs your help! Let Roger provide more detail.
- There might be multiple training coaches, masseurs and physiotherapists depending on the simulation configuration. In this case, every physiotherapist has his/her own service time and training, and massage duration depending on the players need.
- There are exactly three queues in the system: one for training, one for massage and one for physiotherapy. So, each coach shares a common queue and similar for the others.
- The training queue works in first-come-first-served Thus, the first player to enter the queue is served before the others. If two players arrive at the same time, the one with the lower ID is served first. When the training of the player is finished, he/she enters the physiotherapy queue, immediately.
- Since more training time requires more urgent rehabilitation, physiotherapy queue works in a prioritized manner. Therefore, in this queue, the more the training time, the higher the priority. If there are more than one player that have the same training time, then the one that arrived earlier is served before. If they arrived at the same time as well, then the one with the lower ID is served first. Note that, one player may come to the training more than one time, for the prioritization, you should consider only the current training time not the cumulative. Because massage is an advanced service, players should deserve them by their skills. Hence, in the massage queue, the higher the skill level, the earlier the service. If there are more than one player that are in the same skill level, then the one that arrived earlier is served before. If they arrived at the same time as well, then the one with the lower ID is served first
- For all of the services, players visit the first available staff for the service (the available staff with the smallest ID) when they leave the queue.
- Each player is allowed to take at most 3 massage service. Hence, whenever a player attempts to enter the massage queue 4th time, this is called an invalid attempt. Since it is hard for the players to estimate how much time they spend in the queues, there could be some cases such that players may try to come to the training or massage when they are already in the training, physiotherapy or massage process. These attempts should be canceled so they are called canceled attempts.
- One can enter the physiotherapy queue only after the training, no direct entrance is possible.
Below, is a schematic description of the training procedure of his excellency.
Figure 1: A schema of the queues
Therefore, for our purposes, there are two types of events triggered by the players: coming to the training and massage request. Keep also in mind that internal events, such as leaving the training, should also be triggered by the simulation. Roger Federer expects you to simulate the training procedure of ExcelFed using these external and internal discrete events and collect some statistics.
3 Input & Output
3.1 Input
Roger provides all simulation configuration files in the following format:
- The first line contains an integer N that denotes the total number of players in ExcelFed.
- Each of the next N line contains two integer: the ID of the player and his/her skill level. These players will be given in sorted order by ID.
- The next line is the line of an integer A that denotes the total number of arrival to the training and massage.
- Each of the next A lines contains a character At denoting the type of arrival (either m(massage) or t(training)), an integer denoting the ID of the player, the second T that denotes the arrival time, and d duration of the process. These events will not be given in sorted
- The next line comprises an integer Sp that denotes the number of physiotherapists and a list of floats of size Sp. The ith element of the list denotes the service time of the ith
- The last line contains two integers: Sc that denotes the number of training coaches and Sm that denotes the number of masseurs.
Table 1 demonstrates an example input provided by Rafael Nadal, the best consultant in the consultancy team.
| Sample Input File | Explanations |
| 3 | There are 3 players. |
| 0 2 | The player with ID 0 has a skill level 2. |
| 1 3 | The player with ID 1 has a skill level 3. |
| 2 1 | The player with ID 2 has a skill level 1. |
| 9 | There 9 arrivals in total. |
| t 0 1 1.2 | The player with ID 0 arrives for the training at second 1 and the training will take 1.2 seconds. |
| t 1 1.2 2 m 0 6 3 | The player with ID 0 arrives for the massage at second 6 and the massage will take 3 seconds. |
| m 1 6.3 1.8 m 0 10 1.2 t 2 10.1 4 m 0 15 1.2 m 2 16 1.5m 0 20 31 2 | There is 1 physiotherapist and her service time is 2 seconds. |
| 1 1 | There are 1 training coach and 1 masseur. |
Table 1: Sample Input with Explanations
3.2 Output
Roger needs you to collect the following statistics to evaluate the configuration and output them in separate lines, in the order they are given. Please round the statistics to exactly 3 decimal points. In case you cannot report any of the following 15 statistics, print -2 for each of them in order to adhere the output format.
- Maximum length of the training queue.
- Maximum length of the physiotherapy queue.
- Maximum length of the massage queue.
- Average waiting time in the training queue.
- Average waiting time in the physiotherapy queue.
- Average waiting time in the massage queue.
- Average training time.
- Average physiotherapy time.
- Average massage time.
- Average turnaround time (Turnaround time: Total time passed from the training queue entrance until leaving the physiotherapy service.) To compute, sum all turnaround times and divide it by the number of turnarounds, which is also equal to the number of total training arrivals.
- ID of the player who spent the most time in the physiotherapy queue and the waiting time of that player in seconds. If more than one player spent the same amount of time, choose the one with the smallest ID.
- ID of the player who spent the least time in the massage queue and the waiting time of that player in seconds, among the ones who took three massage services. If more than one player spent the same amount of time, choose the one with the smallest ID. If there is no player that took three massage services, print -1 for both.
- Total number of invalid attempts to get a message service.
- Total number of canceled attempts including both training and massage attempts.
- Total seconds passed during the whole simulation.
Nadal also showed the courtesy to share the expected output for the input in Table 2 with explanations. He also showed the progress of queues and services in Table 3 where the numbers in the parenthesis in theservice columns represent the number of remaining seconds to finish the process.
3.3 Java Project Outline
Your java project will be named Project2. Your entry class for the project will be named project2main. All your .java files will be under folder Project2/src. Your project should be compatible with Java 16. Your program will be compiled with below command:
javac Project2/src/*.java -d Project2/bin release 16
The input and output files can be at any folder. Design your code in order to accept full path for file arguments. Your program will be run with below command:
java project2main <inputfile> <outputfile>
Make sure that your final submission compiles and runs with these commands.
| Output File | Explanation |
| 1 | Between seconds 1.2 and 2.2 Player 1 waits for the training. |
| 0 | No one waits for the physiotherapist. |
| 1 | Player 1 and Player 0 waits for the massage but not together so the length of the queue is at most 1. |
| 0.333 | In total, there are 3 training events and only Player 1 waits for 1 second so the answer is 1/3. |
| 0 | No waiting for the physiotherapy queue. |
| 0.875 | Player 1 waits for 2.7 seconds and Player 0 waits for 0.8 seconds so in total 3.5 seconds waiting. Also there are 4 valid massage attempts so 3.5/4. |
| 2.4 | Total training time is 1.2+2+4 so 7.2 and the answer is 7.2/3. |
| 2 | Since there is 1 physiotherapist and her service time is 2 seconds average is also 2 seconds. |
| 1.8 | Total massage time is 3+1.2+1.2+1.8 so 7.2 and there are 4 massage services, the answer is 1.8. |
| 4.733 | Player 0 arrives at 1 and leaves the physiotherapy service at 4.2. Player 1 arrives at 1.2 and leaves the physiotherapy service at 6.2. Player 2 arrives at 10.1 and leaves the physiotherapy service at 16.1. |
| 0 0 | No waiting in physiotherapy queue so the smallest ID is chosen. |
| 0 0.8 | Only Player 0 takes 3 massage services. |
| 1 | Player 1 attempts to take 4 massage services 1 of which is invalid. |
| 1 | Massage attempt by Player 2 at 16 is canceled. |
| 20 | It is the end of the last event which is the invalid massage attempt by Player 0. |
Table 2: Expected Output File and Explanation of each Statistic
| Second | Training Queue | Training Service | Physiotherapy Queue | Physiotherapy Service | Massage Queue | Massage Service |
| 1 | Player 0 (2.2) | |||||
| 1.2 | Player 1 | Player 0 (2.2) | ||||
| 2.2 | Player 1 (4.2) | Player 0 (4.2) | ||||
| 4.2 | Player 1 (6.2) | |||||
| 6 | Player 1 (6.2) | Player 0 (9) | ||||
| 6.2 | Player 0 (9) | |||||
| 6.3 | Player 1 | |||||
| 9 | Player 1 (10.8) | |||||
| 10 | Player 0 | Player 1 (10.8) | ||||
| 10.1 | Player 2 (14.1) | Player 0 | Player 1 (10.8) | |||
| 10.8 | Player 2 (14.1) | Player 0 (12) | ||||
| 12 | Player 2 (14.1) | |||||
| 14.1 | Player 2 (16.1) | |||||
| 15 | Player 0 (16.2) | |||||
| 16.1 | Player 0 (16.2) | |||||
| 16.2 |
Table 3: Step by step progress of the queues and services. Numbers in the parentheses denote the exact second to leave the service.
[1] For further reading about DES you can visit here or Wikipedia
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