//******************************************************************************
//
// File:    MandelbrotSetClu3.java
// Package: edu.rit.clu.fractal
// Unit:    Class edu.rit.clu.fractal.MandelbrotSetClu3
//
// 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.
//
// 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.
//
//******************************************************************************

package edu.rit.clu.fractal;

import edu.rit.color.HSB;

import edu.rit.image.PJGColorImage;
import edu.rit.image.PJGImage;

import edu.rit.io.Files;

import edu.rit.pj.Comm;
import edu.rit.pj.WorkerIntegerForLoop;
import edu.rit.pj.WorkerRegion;
import edu.rit.pj.WorkerTeam;

import edu.rit.util.Range;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;

/**
 * Class MandelbrotSetClu3 is a cluster parallel program that calculates the
 * Mandelbrot Set. The program uses the master-worker pattern for load
 * balancing. Each worker process in the program calculates a series of row
 * slices of the Mandelbrot Set image, as assigned by the master process. Each
 * worker writes its own slices to its own (partial) PJG image file. The
 * per-worker image files can be combined offline into a single image file if
 * desired.
 * 

 * The row slices are determined by the pj.schedule property specified
 * on the command line; the default is to divide the rows evenly among the
 * processes (i.e. no load balancing). For further information about the
 * pj.schedule property, see class {@linkplain edu.rit.pj.PJProperties
 * PJProperties}.
 * 

 * Usage: java -Dpj.np=K [ -Dpj.schedule=schedule ]
 * edu.rit.clu.fractal.MandelbrotSetClu3 width height
 * xcenter ycenter resolution maxiter gamma
 * filename
 * 
K = Number of parallel processes
 * 
schedule = Load balancing schedule
 * 
width = Image width (pixels)
 * 
height = Image height (pixels)
 * 
xcenter = X coordinate of center point
 * 
ycenter = Y coordinate of center point
 * 
resolution = Pixels per unit
 * 
maxiter = Maximum number of iterations
 * 
gamma = Used to calculate pixel hues
 * 
filename = PJG image file name
 * 

 * If filename is specified as, for example, "image.pjg", then
 * the per-worker image files are named "image_0.pjg",
 * "image_1.pjg", and so on through K-1.
 * 

 * The program considers a rectangular region of the complex plane centered at
 * (xcenter,ycenter) of width pixels by height pixels,
 * where the distance between adjacent pixels is 1/resolution. The
 * program takes each pixel's location as a complex number c and performs
 * the following iteration:
 * 

 * z0 = 0
 * 
zi+1 = zi2 + c
 * 

 * until zi's magnitude becomes greater than or equal
 * to 2, or i reaches a limit of maxiter. The complex numbers
 * c where i reaches a limit of maxiter are considered to
 * be in the Mandelbrot Set. (Actually, a number is in the Mandelbrot Set only
 * if the iteration would continue forever without zi
 * becoming infinite; the foregoing is just an approximation.) The program
 * creates an image with the pixels corresponding to the complex numbers
 * c and the pixels' colors corresponding to the value of i
 * achieved by the iteration. Following the traditional practice, points in the
 * Mandelbrot set are black, and the other points are brightly colored in a
 * range of colors depending on i. The exact hue of each pixel is
 * (i/maxiter)gamma. The image is stored in a
 * Parallel Java Graphics (PJG) file specified on the command line.
 * 

 * The computation is performed in parallel in multiple processors. The program
 * measures the computation's running time, including the time to write the
 * image file.
 *
 * @author  Alan Kaminsky
 * @version 26-Dec-2009
 */
public class MandelbrotSetClu3
	{

// Prevent construction.

	private MandelbrotSetClu3()
		{
		}

// Program shared variables.

	// Communicator.
	static Comm world;
	static int size;
	static int rank;

	// Command line arguments.
	static int width;
	static int height;
	static double xcenter;
	static double ycenter;
	static double resolution;
	static int maxiter;
	static double gamma;
	static File filename;

	// Initial pixel offsets from center.
	static int xoffset;
	static int yoffset;

	// Image matrix.
	static int[][] matrix;
	static PJGColorImage image;
	static PJGImage.Writer writer;

	// Table of hues.
	static int[] huetable;

	// Number of chunks the worker computed.
	static int chunkCount;

// Main program.

	/**
	 * Mandelbrot Set main program.
	 */
	public static void main
		(String[] args)
		throws Exception
		{
		// Start timing.
		long t1 = System.currentTimeMillis();

		// Initialize middleware.
		Comm.init (args);
		world = Comm.world();
		size = world.size();
		rank = world.rank();

		// Validate command line arguments.
		if (args.length != 8) usage();
		width = Integer.parseInt (args[0]);
		height = Integer.parseInt (args[1]);
		xcenter = Double.parseDouble (args[2]);
		ycenter = Double.parseDouble (args[3]);
		resolution = Double.parseDouble (args[4]);
		maxiter = Integer.parseInt (args[5]);
		gamma = Double.parseDouble (args[6]);
		filename = new File (args[7]);

		// Initial pixel offsets from center.
		xoffset = -(width - 1) / 2;
		yoffset = (height - 1) / 2;

		// Allocate storage for pixel matrix row references only.
		matrix = new int [height] [];

		// Prepare to write image row slices to per-worker PJG image file.
		image = new PJGColorImage (height, width, matrix);
		writer =
			image.prepareToWrite
				(new BufferedOutputStream
					(new FileOutputStream
						(Files.fileForRank (filename, rank))));

		// Create table of hues for different iteration counts.
		huetable = new int [maxiter+1];
		for (int i = 0; i < maxiter; ++ i)
			{
			huetable[i] = HSB.pack
				(/*hue*/ (float) Math.pow (((double)i)/((double)maxiter),gamma),
				 /*sat*/ 1.0f,
				 /*bri*/ 1.0f);
			}
		huetable[maxiter] = HSB.pack (1.0f, 1.0f, 0.0f);

		long t2 = System.currentTimeMillis();

		// Compute pixels in parallel.
		new WorkerTeam().execute (new WorkerRegion()
			{
			public void run() throws Exception
				{
				execute (0, height-1, new WorkerIntegerForLoop()
					{
					// Storage for row slice of pixels.
					int[][] slice = new int [0] [];

					// Compute chunk of pixels, rows lb .. ub.
					public void run (int lb, int ub) throws Exception
						{
						// Count chunks.
						++ chunkCount;

						// Allocate storage for row slice if necessary.
						int len = ub - lb + 1;
						if (slice.length < len)
							{
							slice = new int [len] [width];
							}

						// Compute pixels.
						for (int r = lb; r <= ub; ++ r)
							{
							int[] slice_r = slice[r-lb];
							double y = ycenter + (yoffset - r) / resolution;

							for (int c = 0; c < width; ++ c)
								{
								double x = xcenter + (xoffset + c) / resolution;

								// Iterate until convergence.
								int i = 0;
								double aold = 0.0;
								double bold = 0.0;
								double a = 0.0;
								double b = 0.0;
								double zmagsqr = 0.0;
								while (i < maxiter && zmagsqr <= 4.0)
									{
									++ i;
									a = aold*aold - bold*bold + x;
									b = 2.0*aold*bold + y;
									zmagsqr = a*a + b*b;
									aold = a;
									bold = b;
									}

								// Record number of iterations for pixel.
								slice_r[c] = huetable[i];
								}
							}

						// Set full pixel matrix rows to refer to slice rows.
						System.arraycopy (slice, 0, matrix, lb, len);

						// Write row slice of full pixel matrix to image file.
						writer.writeRowSlice (new Range (lb, ub));
						}
					});
				}
			});

		long t3 = System.currentTimeMillis();

		// Close image file.
		writer.close();

		// Stop timing.
		long t4 = System.currentTimeMillis();
		System.out.println (chunkCount + " chunks " + rank);
		System.out.println ((t2-t1) + " msec pre " + rank);
		System.out.println ((t3-t2) + " msec calc " + rank);
		System.out.println ((t4-t3) + " msec post " + rank);
		System.out.println ((t4-t1) + " msec total " + rank);
		}

// Hidden operations.

	/**
	 * Print a usage message and exit.
	 */
	private static void usage()
		{
		System.err.println ("Usage: java -Dpj.np= [-Dpj.schedule=] edu.rit.clu.fractal.MandelbrotSetClu3        ");
		System.err.println (" = Number of parallel processes");
		System.err.println (" = Load balancing schedule");
		System.err.println (" = Image width (pixels)");
		System.err.println (" = Image height (pixels)");
		System.err.println (" = X coordinate of center point");
		System.err.println (" = Y coordinate of center point");
		System.err.println (" = Pixels per unit");
		System.err.println (" = Maximum number of iterations");
		System.err.println (" = Used to calculate pixel hues");
		System.err.println (" = PJG image file name");
		System.exit (1);
		}

	}