StratifiedUnitCubeAnti.java

/*
 * Class:        StratifiedUnitCubeAnti
 * Description:  
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       
 * @since
 
 * SSJ is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License (GPL) as published by the
 * Free Software Foundation, either version 3 of the License, or
 * any later version.
 
 * SSJ 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 available at
   <a href="http://www.gnu.org/licenses">GPL licence site</a>.
 */
package umontreal.ssj.hups;
 
import umontreal.ssj.rng.RandomStream;

public class StratifiedUnitCubeAnti extends CachedPointSet {

   protected int[] numDiv; // Number of divisions in each dimension, k_j

   protected double[] delta;

   public StratifiedUnitCubeAnti(int[] k, int dim) {
      this.dim = dim;
      delta = new double[dim];
      numDiv = new int[dim];
      numPoints = 2;
      for (int j = 0; j < dim; j++) {
         numDiv[j] = k[j];
         numPoints *= k[j];
         delta[j] = 1.0 / (double) numDiv[j];
      }
      x = new double[numPoints][dim];
   }

   public StratifiedUnitCubeAnti(int k, int dim) {
      this.dim = dim;
      delta = new double[dim];
      numDiv = new int[dim];
      numPoints = 2;
      for (int j = 0; j < dim; j++) {
         numDiv[j] = k;
         numPoints *= k;
         delta[j] = 1.0 / (double) k;
      }
      x = new double[numPoints][dim];
   }

   public void randomize(RandomStream stream) {
      int i;
      double u;
      int[] current = new int[dim]; // current[j] = current division for
                                    // dim j when we enumerate the points
      for (int j = 0; j < dim; j++)
         current[j] = 0;
      int numBoxes = numPoints / 2;
      for (int b = 0; b < numBoxes; b++) {
         // Generate random point i=2b in box b, and compute locally antithetic point
         // i+1.
         i = 2 * b;
         for (int j = 0; j < dim; j++) {
            u = stream.nextDouble();
            x[i][j] = (current[j] + u) * delta[j];
            x[i + 1][j] = (current[j] + 1.0 - u) * delta[j];
         }
         // Find the next box.
         for (int l = 0; l < dim; l++) {
            current[l]++;
            if (current[l] >= numDiv[l])
               current[l] = 0; // next, we will add the carry to current[l+1].
            else
               l = dim; // Exit loop.
         }
      }
   }

   public void addRandomShift(int fromDim, int toDim, RandomStream stream) {
      randomize(stream);
   }

   public void randomize(PointSetRandomization rand) {
      randomize(rand.getStream());
   }
 
   public String toString() {
      return "StratifiedUnitCubeAnti: locally antithetic stratified point set over the unit cube in " + dim
            + "dimensions.";
   }
}