//******************************************************************************
   //
   // File:    DynamicIntegerSchedule.java
   // Package: edu.rit.pj
   // Unit:    Class edu.rit.pj.DynamicIntegerSchedule
   //
   // This Java source file is copyright (C) 2009 by Alan Kaminsky. All rights
   // reserved. For further information, contact the author, Alan Kaminsky, at
   // ark@cs.rit.edu.
  //
  // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
  // software; you can redistribute it and/or modify it under the terms of the GNU
  // General Public License as published by the Free Software Foundation; either
  // version 3 of the License, or (at your option) any later version.
  //
  // PJ is distributed in the hope that it will be useful, but WITHOUT ANY
  // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  // A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  //
  // Linking this library statically or dynamically with other modules is making a
  // combined work based on this library. Thus, the terms and conditions of the GNU
  // General Public License cover the whole combination.
  //
  // As a special exception, the copyright holders of this library give you
  // permission to link this library with independent modules to produce an
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  // statement from your version.
  //
  // A copy of the GNU General Public License is provided in the file gpl.txt. You
  // may also obtain a copy of the GNU General Public License on the World Wide
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  //
  //******************************************************************************
  package edu.rit.pj;
  
  import java.util.concurrent.atomic.AtomicInteger;
  
  import edu.rit.util.Range;
  
  /**
   * Class DynamicIntegerSchedule provides a dynamic schedule object. The loop
   * index is type <code>int</code>. The loop iterations are apportioned into chunks
   * of a given size (a given number of iterations per chunk). Each parallel team
   * thread repeatedly performs the next available chunk of iterations until there
   * are no more chunks. The final chunk may be smaller than the given chunk size.
   *
   * @author Alan Kaminsky
   * @version 17-Nov-2009
   */
  class DynamicIntegerSchedule
          extends IntegerSchedule {
  
  // Hidden data members.
      // Loop iteration range.
      private Range myLoopRange;
  
      // Number of iterations already handed out.
      private AtomicInteger N1 = new AtomicInteger();
  
      // Chunk size.
      private int N2;
  
  // Exported constructors.
      /**
       * Construct a new dynamic schedule object with a chunk size of 1.
       */
      public DynamicIntegerSchedule() {
          this(1);
      }
  
      /**
       * Construct a new dynamic schedule object with the given chunk size.
       *
       * @param theChunkSize Chunk size.
       * @exception IllegalArgumentException (unchecked exception) Thrown if
       * <code>theChunkSize</code> is less than 1.
       */
      public DynamicIntegerSchedule(int theChunkSize) {
          super();
          if (theChunkSize < 1) {
              throw new IllegalArgumentException("DynamicIntegerSchedule(): Chunk size = " + theChunkSize
                      + " illegal");
          }
          N2 = theChunkSize;
      }
  
      /**
       * Construct a new dynamic schedule object. This constructor is for use by
       * the <code>IntegerSchedule.parse()</code> method. <code>args</code> must be an
       * array of one string, namely the chunk size, an integer &gt;= 1.
       *
       * @param args Array of argument strings.
       * @exception IllegalArgumentException (unchecked exception) Thrown if
      * <code>args</code> is not an array of one string. Thrown if the chunk size is
      * less than 1.
      */
     public DynamicIntegerSchedule(String[] args) {
         this(getChunkSize(args));
     }
 
     private static int getChunkSize(String[] args) {
         if (args.length != 1) {
             throw new IllegalArgumentException("DynamicIntegerSchedule(): Usage: -Dpj.schedule=dynamic or -Dpj.schedule=\"dynamic(<n>)\"");
         }
         int theChunkSize;
         try {
             theChunkSize = Integer.parseInt(args[0]);
         } catch (NumberFormatException exc) {
             throw new IllegalArgumentException("DynamicIntegerSchedule(): Chunk size = " + args[0]
                     + " illegal");
         }
         return theChunkSize;
     }
 
     /**
      * Determine if this schedule is a fixed schedule. For a parallel team with
      * <I>K</I> threads, a fixed schedule partitions the loop index range into
      * exactly <I>K</I> chunks, one chunk for each thread, each chunk with
      * predetermined upper and lower bounds.
      *
      * @return True if this is a fixed schedule, false otherwise.
      */
     public boolean isFixedSchedule() {
         return false;
     }
 
 // Hidden operations.
     /**
      * {@inheritDoc}
      *
      * Start generating chunks of iterations for a parallel for loop using this
      * schedule.
      * <P>
      * The <code>start()</code> method is only called by a single thread in the
      * Parallel Java middleware.
      */
     public void start(int K,
             Range theLoopRange) {
         myLoopRange = theLoopRange;
         N1.set(0);
     }
 
     /**
      * {@inheritDoc}
      *
      * Obtain the next chunk of iterations for the given thread index. If there
      * are more iterations, a range object is returned whose lower bound, upper
      * bound, and stride specify the chunk of iterations to perform. The
      * returned range object's stride is the same as that given to the
      * <code>start()</code> method. The returned range object's lower bound and
      * upper bound are contained within the range given to the <code>start()</code>
      * method. If there are no more iterations, null is returned.
      * <P>
      * The <code>next()</code> method is called by multiple parallel team threads in
      * the Parallel Java middleware. The <code>next()</code> method must be multiple
      * thread safe.
      */
     public Range next(int theThreadIndex) {
         for (;;) {
             int oldN1 = N1.get();
             Range result = myLoopRange.chunk(oldN1, N2);
             int N = result.length();
             if (N == 0) {
                 return null;
             }
             int newN1 = oldN1 + N;
             if (N1.compareAndSet(oldN1, newN1)) {
                 return result;
             }
         }
     }
 
 }