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--- lab7 [2017/02/18 20:31] – franck
+++ lab7 [2018/03/11 23:19] (current) – franck
@@ Line 1: / Line 1: @@
-The beam search strategy uses the breadth-first search strategy to build its state space.  At each level of the search tree, it generates only a limited number of successors of the states at the current level.  To simplify matters, we limit that number to two.  In general, the beam search strategy would pick the two "best" successors.  Again, to simplify matters, our beam search strategy will select the two "left-most" successors.  Consider, for example, the following state space diagram.
+====== Lab 7 ======
-{{:public:beamsearch.png|}}
+In this lab, we consider a concurrent stack.  We start from the following skeleton of a sequential stack.  Note that the class Stack does not implement a stack correctly.
+<code java>
+/**
+ * A stack.  It stores integers.
+ *
+ * @author
+ */
+public class Stack {
+  private int[] content;
+  private int size;
-While traversing the state space, the beam search strategy will visit the states labelled A, B, C, E and F.
+  /*
+   * The maximal number of integers that can be stored in a stack.
+   */
+  private final static int CAPACITY = 5;
-Create a search strategy, named BeamSearch, which implements the beam search strategy.  Only add notifications related to SearchListeners (no need for dealing with the attribute done, etcetera).
+  /**
+   * Initializes this stack to be empty.
+   */
+  public Stack() {
+    this.content = new int[Stack.CAPACITY];
+    this.size = 0;
+  }
-To receive feedback, submit your test case using the submit command before Tuesday Febraury 28:\\
+  /**
-submit 4315 lab7 BeamSearch.java
+   * Pushes the given integer onto this stack.
+   *
+   * @param value the integer to be pushed onto this stack.
+   */
+  public void push(int value) {
+    this.content[this.size] = value;
+    this.size++;
+    System.out.printf("Push %d\n", value);
+  }
+  /**
+   * Pops the top of this stack and returns the integer.
+   *
+   * @return the top of this stack.
+   */
+  public int pop() {
+    this.size--;
+    int value = this.content[this.size];
+    System.out.printf("Pop %d\n", value);
+    return value;
+  }
+}
+</code>
+Implement the following classes.
+  * The class Pusher.  Each Pusher object is a Thread that pushes the integers 0, 1, ..., 9 onto a stack.  The stack is provided as an argument to the constructor of the Pusher class.  The jar file {{:pop.jar|pop.jar}} contains the class Popper.  Each Popper object is a Thread that pops ten integers from a stack.  The stack is provided as an argument to the constructor of the Popper class.
+  * The class Stack.  This class is based on the above skeleton and allows Threads to concurrently call the push and pop methods on the stack.
+  * The class Main.  This class only contains a main method.  In the main method, a number of Popper and Pusher objects are created (for example, 10 Poppers and 5 Pushers) and all these Threads are run concurrently.
+To receive feedback, submit your code using the submit command:\\
+<code>
+submit 4315 lab7 <name of class>.java
+</code>