HammersleyPointSet.java

/*
 * Class:        HammersleyPointSet
 * Description:  
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       
 * @since
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package umontreal.ssj.hups;

public class HammersleyPointSet extends PointSet {
   private int[] base; // Vector of prime bases.
   private int[][] permutation; // Digits permutation, for each dimension.
   private boolean permuted; // Permute digits?

   public HammersleyPointSet(int n, int dim) {
      if (n < 0 || dim < 1)
         throw new IllegalArgumentException("Hammersley point sets must have positive dimension and n >= 0");
      numPoints = n;
      this.dim = dim;
      if (dim > 1)
         base = RadicalInverse.getPrimes(dim - 1);
   }

   public void addFaurePermutations() {
      if (dim > 1) {
         permutation = new int[dim][];
         for (int i = 0; i < dim - 1; i++) {
            permutation[i] = new int[base[i]];
            RadicalInverse.getFaurePermutation(base[i], permutation[i]);
         }
      }
      permuted = true;
   }

   public void ErasePermutations() {
      permuted = false;
      permutation = null;
   }
 
   public double getCoordinate(int i, int j) {
      if (j == 0)
         return (double) i / (double) numPoints;
      if (permuted)
         return RadicalInverse.permutedRadicalInverse(base[j - 1], permutation[j - 1], i);
      else
         return RadicalInverse.radicalInverse(base[j - 1], i);
   }
}