Question

1. The first task in this assignment creates the pid manager whose implementation can simply be a single class. Of course, you can create any other classes you might need to implement the pid manager. You may use any data structure of your choice to represent the availability of process identifiers. One strategy adopts Linux’s approach of a bitmap in which a value of 0 at position i indicates that a process id of value i is available and a value of 1 indicates that the process id is currently in use. Use the following constants to identify the range of possible pid values: MIN_PID is 300 and MAX_PID is 5000. Have your pid manager implement the following API for obtaining and releasing a pid:

 int allocateMap( ) – Creates and initializes a data structure for representing pids; returning 0 if unsuccessful or 1 if successful.

 int allocatePid( ) – Allocates and returns a pid; returns 1 if unable to allocate a pid, all pids are in use.

 void releasePid(int pid) – Releases a pid.

2. The second task in this assignment consists of writing a multithreaded program that tests your pid manager. Implementing the threads uses either extends Thread or implements Runnable. Create a number of threads where each thread requests a pid, sleeps for a random period of time, releases the pid, and then terminates. Sleeping for a random period of time approximates the typical pid usage in which a new process acquires a pid, the process executes and then terminates, releasing the pid upon its termination. Download the SleepUtilities.java file needed for the assignment. A thread sleeps by calling the SleepUtilities.nap(duration) function, passing an integer value representing the number of seconds to sleep, where duration is a randomly generated integer between 60 and 300. Before sleeping, each thread should print out (on a new line) the message, “My PID is: x.”, where x is the actual pid for the thread.

//SleepUtilities.java

public class SleepUtilities
{
  private static final int NAP_TIME = 5;

  // Nap between zero and NAP_TIME seconds.
  public static void nap()
  {
    nap(NAP_TIME);
  }

  // Nap between zero and duration seconds.
  public static void nap(int duration)
  {
    int sleeptime = (int) (duration * Math.random());

    try
    {
     Thread.sleep(sleeptime * 1000);
    }
    catch (InterruptedException e) { }
  }
}

3. Create a driver class and make the name of the driver class Assignment1 containing only one method: public static void main(String args[]). The main method itself is fairly short containing code to do the following:

a. Create the pid manager object.

b. Create 100 threads.

c. For each thread, pass the pid manager into the thread and begin the execution of the thread.

d. The main method needs to keep track of the threads and take care of each thread before it can end. The methods of the Thread class you'll need for this are join() and isAlive(). If the thread is dead then execute a join on it in order to properly dispose of that thread. If the thread is still alive then move on to the next thread. The main method keeps doing this check until the last remaining thread has died and been properly disposed.

Answer 1