BatchSortPow2.java

/*
 * Class:        BatchSortPow2
 * Description:  performs a batch sort on an array, batch numbers must be powers of 2.
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2015  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.util.multidimsort;

public class BatchSortPow2<T extends MultiDimComparable<? super T>> extends BatchSort<T> {
   int[] ej; // The current exponents e_j.

   public BatchSortPow2(double[] batchExponents) {
      super(batchExponents);
      ej = new int[this.dimension];
   }

   public void setBatchNumbers(int n) {
      if (batchExponents == null)
         throw new NullPointerException("batchExponents is null");
      // Round up to the nearest power of 2. Will be 2^e.
      int e = 1;
      while (n > (1 << e))
         e++;
      nSaved = n;
      batchProduct = 1 << e; // Product of batch numbers = p = 2^e.
      for (int j = 0; j < dimension; ++j) {
         ej[j] = (int) Math.ceil(e * batchExponents[j]); // log_2 of num of batches.
         e -= ej[j]; // The power of 2 that remains for each batch.
         batchNumbers[j] = 1 << ej[j];
      }
   }

   public int[] getBitNumbers() {
      return ej;
   }
 
}