====== Solutions for assignments in Parallele Programmierung. ======
See [[eth:ETH]]. [[ParallelPrefix]]
===== Assignment 1 =====
 
<code java>
/**
 * 
 * @author Moritz Hoffmann
 * 
 */
public class Assignment1 {

    /**
     * Main method
     * 
     * @param args
     *            List of numbers.
     */
    public static void main(String[] args) {
        int max = (1 << 16) - 1;
        int min = (-1 ^ (1 << 16)) + 1;
        for (String str : args) {
            try {
                int i = Integer.parseInt(str);
                if (i >= min && i <= max) {
                    System.out.println(i + 1);
                } else {
                    System.out.println("Number " + i + " out of range.");
                }
            } catch (NumberFormatException e) {
                System.out.println("Failed to convert to number: " + str);
            }
        }
    }
}
</code>
===== Assignment 2 =====
<code java>
/**
 * 
 * @author Moritz Hoffmann
 * 
 */
public class Assignment2 {
    private final class MyException extends Exception {

        public MyException() {
            super();
        }

        public MyException(String message) {
            super(message);
        }

        public MyException(String message, Throwable cause) {
            super(message, cause);
        }

        public MyException(Throwable cause) {
            super(cause);
        }
    }

    /**
     * Main method
     * 
     * @param args
     *            List of numbers.
     */
    public static void main(String[] args) {
        new Assignment2().process(args);
    }

    /**
     * Process the string array.
     * 
     * @param args
     *            Same as from {@link Assignment1#main(String[])}
     */
    private void process(String[] args) {
        for (String str : args) {
            try {
                int i = Integer.parseInt(str);
                try {
                    if (i < 0) {
                        throw new MyException(Integer.toString(i));
                    }
                    System.out.println(i + 1);
                } catch (MyException e) {
                    System.err.println("Negative value " + e.getMessage()
                            + " -- bailing out.");
                    break;
                }
            } catch (NumberFormatException e) {
                System.out.println("Failed to convert to number: " + str);
            }
        }
    }
}
</code>

Bounded buffer for assignment 3:
<code java>
package hw03;

public class BoundedBuffer implements Buffer {
    private static final int SIZE = 5;

    private final int[] buffer = new int[SIZE];
    private int pos = -1;

    public int read() throws BufferEmptyException {
        return get();
    }

    public void write(int i) throws BufferFullException {
        set(i);
    }

    private synchronized int get() {
        while (pos == -1) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        // the first element
        int v = buffer[0];
        System.arraycopy(buffer, 1, buffer, 0, pos);
        pos = pos - 1;
        this.notifyAll();
        return v;
    }

    private synchronized void set(int v) {
        System.out.println(pos);
        while (pos >= SIZE - 1) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        pos = pos + 1;
        buffer[pos] = v;
        this.notifyAll();
    }

}
</code>

===== Assignment 4 =====
<code java>
package hw04;

public class MTMergeSort {

    /**
     * A sorter runnable. This will create as many sub threads as passed by the
     * threads parameter. If it is an odd number, one half will be sorted using
     * a thread, the other will be sorted by this object.
     * 
     * @author Moritz Hoffmann
     * 
     */
    private final class Sorter implements Runnable {
        private final int l, r;
        private final Thread left, right;
        private final int middle;
        private final SeqMergeSort sorter;

        Sorter(int left, int right, int threads, SeqMergeSort sorter) {
            this.sorter = sorter;
            threads = threads - 1;
            l = left;
            r = right;
            middle = (l + r) / 2;
            if (threads > 1) {
                // construct both left and right threads
                final int thalf = threads / 2;
                this.left = new Thread(new Sorter(l, middle, threads - thalf,
                    sorter));
                this.right = new Thread(
                    new Sorter(middle + 1, r, thalf, sorter));
            } else if (threads == 1) {
                // construct only left thread, right part will be sorted by
                // this.
                this.left = new Thread(new Sorter(l, middle, 0, sorter));
                this.right = null;
            } else {
                this.left = this.right = null;
            }
        }

        public void run() {
            // System.out.println("Running " + Thread.currentThread().getId());
            if (this.left == null && this.right == null) {
                // sort here
                sorter.mergesort(l, r);
            } else if (this.left != null && this.right == null) {
                // let left sort in background
                this.left.start();
                // sort here
                sorter.mergesort(middle + 1, r);
                try {
                    // wait for left to finish.
                    this.left.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // merge the results together.
                sorter.merge(l, middle, middle + 1, r);
            } else {
                // sort both left and right in a separate thread.
                left.start();
                right.start();
                try {
                    left.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                try {
                    right.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // merge the results together.
                sorter.merge(l, middle, middle + 1, r);
            }
            // System.out.println("Returning " +
            // Thread.currentThread().getId());
        }
    }

    private final int[] to_sort;

    private final int total_sort_threads;

    public MTMergeSort(int[] to_sort, int no_threads) {
        this.to_sort = to_sort;
        this.total_sort_threads = no_threads;
    }

    public void sort() {
        // Your code here to perform multithreaded merge sort
        // You should use SeqMergeSort.sort() and SeqMergeSort.merge()
        // for sorting and merging, respectively.
        // total number of sorting threads = this.total_sort_threads

        // The shared sorter instance.
        SeqMergeSort mergesort = new SeqMergeSort(to_sort);
        // construct a new sorter instance.
        Sorter s = new Sorter(0, to_sort.length - 1, total_sort_threads,
            mergesort);
        // call it synchronously as it can use the main thread as well.
        long t = System.nanoTime();
        s.run();
        System.out.println((double) (System.nanoTime() - t) / 1000000 + "[ms]");
    }

}
</code>