marvinjason / cpuscheduler

Java implementation of 6 CPU scheduling algorithms

CPUScheduler

Java implementation of 6 CPU scheduling algorithms: First Come First Serve (FCFS), Shortest Job First (SJF), Shortest Remaining Time (SRT), Priority Non-preemptive (PSN), Priority Preemptive (PSP), and Round Robin (RR).

Usage

Instantiate a CPUScheduler object of the algorithm

CPUScheduler fcfs = new FirstComeFirstServe();

Add a new Row for every job queued

fcfs.add(new Row("P1", 0, 5));
fcfs.add(new Row("P2", 2, 4));
fcfs.add(new Row("P3", 4, 3));
fcfs.add(new Row("P4", 6, 6));

Call the process method

fcfs.process();

Use the accessors

fcfs.getAverageWaitingTime();     // 3.5
fcfs.getAverageTurnAroundTime();  // 8.0

Round Robin

In the case of RoundRobin, you must first set a time quantum before calling process.

CPUScheduler rr = new RoundRobin();

rr.add(new Row("P1", 0, 5));
rr.add(new Row("P2", 2, 4));
rr.add(new Row("P3", 4, 3));
rr.add(new Row("P4", 6, 6));

rr.setTimeQuantum(2);
rr.process();

Rows

Using the object's getRows method will return a List of all queued Row. After process, each Row will reflect their respective computed waiting time and turnaround time.

CPUScheduler sjf = new ShortestJobFirst();
List<Row> rows;

sjf.add(new Row("P1", 0, 5));
sjf.add(new Row("P2", 2, 4));

rows = sjf.getRows();
rows.get(1).getWaitingTime();     // 0
rows.get(1).getTurnaroundTime();  // 0

sjf.process();

rows = sjf.getRows();
rows.get(1).getWaitingTime();     // 3
rows.get(1).getTurnaroundTime();  // 7

Timeline

Using the object's getTimeline method will return a List of Event which can be used to draw a Gantt chart. The timeline shows what job is being processed at the given time.

List<Event> timeline = fcfs.getTimeline();

for (Event event : timeline)
{
  System.out.println(event.getStartTime());
  System.out.println("|  " + event.getProcessName());
}

System.out.print(timeline.get(timeline.size() - 1).getFinishTime());

Result:

0
|  P1
5
|  P2
9
|  P3
12
|  P4
18

Example

An example can be found here.

Demo

A Java Swing application using the library is included within the project.

Screenshots

cpuscheduler's Issues

How to read inputs from a txt file

How can I read values for all the functions using a txt file unlike via add row method

Missing Idle process status, Round Robin miscalculation

Context: I'm lazy and I was looking for a CPU scheduling app instead of taking the time to calculate everything manually.

This was working pretty well for small assignments, and I loved how it gave the waiting time and turnaround time too, besides the Gantt chart.

But just in case someone else is also using this app, take note it excludes when the process is currently idle, which messes up the calculations. Plus, I wouldn't rely on the RR algorithm too. It might be right for some of you, but it's best to double-check your work.