Parallel Programming WS 2014/2015 - Assignment 4

Kastens, Pfahler
Institut für Informatik, Fakultät für Elektrotechnik, Informatik und Mathematik, Universität Paderborn

Dec 08, 2014

Exercise 1 (Rendezvous: The Fürstenallee Shuttle)

A new driverless shuttle train connects the Fürstenallee building with the University campus. It consists of a single rail car with seats for 8 passengers. The shuttle only starts if the car is fully occupied.

We apply the design method for the rendezvous of processes to design a monitor for the FA shuttle simulation. The following illustration shows the entry procedures and the counter variables:

a)

Determine the monitor invariant.

b)

Determine the waiting conditions and the counter increments (Slide 36). Fill in the following table:

Entry Procedure	wait while ...	Modify counters
ride
offer
offer

c)

Substitute the increasing counters by limited counters.

d)

LAB: Implement a Java monitor class that can be used with the FA shuttle simulation in directory blatt4/FAShuttle.

(Here is the Solution for Exercise 1)

Exercise 2 (Barrier Synchronization: Rolling Dices)

We use N dices to generate endless sequences of random numbers:

   public class DiceTest {
       final static int N = 4;
       public static void main(String[] args) {
           DiceBarrier x = new DiceBarrier(N);
   
           for (int i = 1; i <= N; i++) {
               new Dice(i, x).start();
           }
       }
   }

The results of each round have to be added and output. Therefore the dices have to be synchronized using a barrier after each throw:

   public class Dice extends Thread {
       private DiceBarrier x;
       private int number;
       private int val;
      
       public Dice(int number, DiceBarrier x) {
           this.number = number;
           this.x = x;
       }
   
       public void run() {
           while (true) {
               val = (int) (Math.random() * 6) + 1;
               x.barrier(number, val);
           }
       }
   }

Use a simple shared counter barrier (Slide 44) to complete the implementation (blatt4/dices) of class DiceBarrier:

   public class DiceBarrier {
      private final int N; // number of dices
      
      DiceBarrier(int n)  { 
           N = n;
      }
      
      synchronized public void barrier(int dicenumber, int value) {
       // to be completed
       }
   }

Hint: The barrier method is also responsible for computing the sum of the dice values. The dicenumber parameter can be used to generate log output like:

   Dice 4 arrived
   Dice 2 arrived
   Dice 3 arrived
   Dice 1 arrived
   Sum = 15
   Dice 1 arrived
   Dice 4 arrived
   Dice 2 arrived
   Dice 3 arrived
   Sum = 17
   ...

(Here is the Solution for Exercise 2)

Generiert mit Camelot | Probleme mit Camelot? | Geändert am: 05.01.2015

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