//******************************************************************************
//
// File:    FixedLongSchedule.java
// Package: edu.rit.pj
// Unit:    Class edu.rit.pj.FixedLongSchedule
//
// This Java source file is copyright (C) 2010 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
// executable, regardless of the license terms of these independent modules, and
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// exception 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
// Web at http://www.gnu.org/licenses/gpl.html.
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//******************************************************************************

package edu.rit.pj;

import edu.rit.util.LongRange;

/**
 * Class FixedLongSchedule provides a fixed schedule object. The loop index
 * is type <TT>long</TT>. The loop iterations are apportioned among the parallel
 * team threads once at the beginning of the parallel for loop, with each thread
 * getting a fixed number of iterations, the same number of iterations for each
 * thread (plus or minus one).
 *
 * @author  Alan Kaminsky
 * @version 27-Jan-2010
 */
class FixedLongSchedule
	extends LongSchedule
	{

// Hidden data members.

	// Chunk for each thread.
	private LongRange[] myChunk;

// Exported constructors.

	/**
	 * Construct a new fixed schedule object.
	 */
	public FixedLongSchedule()
		{
		super();
		}

	/**
	 * Construct a new fixed schedule object. This constructor is for use by the
	 * <TT>LongSchedule.parse()</TT> method.
	 *
	 * @param  args  Array of argument strings.
	 */
	public FixedLongSchedule
		(String[] args)
		{
		super();
		throw new IllegalArgumentException
			("FixedLongSchedule(): Usage: -Dpj.schedule=fixed");
		}

// Exported operations.

	/**
	 * 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 true;
		}

// Hidden operations.

	/**
	 * Start generating chunks of iterations for a parallel for loop using this
	 * schedule.
	 * <P>
	 * The <TT>start()</TT> method is only called by a single thread in the
	 * Parallel Java middleware.
	 *
	 * @param  K             Number of threads in the parallel team.
	 * @param  theLoopRange  Range of iterations for the entire parallel for
	 *                       loop. The stride may be 1 or greater.
	 */
	public void start
		(int K,
		 LongRange theLoopRange)
		{
		myChunk = theLoopRange.subranges (K);
		for (int i = 0; i < K; ++ i)
			{
			if (myChunk[i].length() == 0) myChunk[i] = null;
			}
		}

	/**
	 * 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
	 * <TT>start()</TT> method. The returned range object's lower bound and
	 * upper bound are contained within the range given to the <TT>start()</TT>
	 * method. If there are no more iterations, null is returned.
	 * <P>
	 * The <TT>next()</TT> method is called by multiple parallel team threads in
	 * the Parallel Java middleware. The <TT>next()</TT> method must be multiple
	 * thread safe.
	 *
	 * @param  theThreadIndex  Thread index in the range 0 .. <I>K</I>-1.
	 *
	 * @return  Chunk of iterations, or null if no more iterations.
	 */
	public LongRange next
		(int theThreadIndex)
		{
		LongRange chunk = myChunk[theThreadIndex];
		myChunk[theThreadIndex] = null;
		return chunk;
		}

	}
