SkewedLatestGenerator.java

/**
 * Copyright (c) 2010 Yahoo! Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */
package com.googlecode.concurrentlinkedhashmap.generator;

/**
 * Generate a popularity distribution of items, skewed to favor recent items
 * significantly more than older items.
 *
 * @author Brian Cooper
 * @see <a href="http://research.yahoo.com/Web_Information_Management/YCSB">YCSB</a>
 */
public class SkewedLatestGenerator extends IntegerGenerator {
  CounterGenerator _basis;
  ZipfianGenerator _zipfian;

  public SkewedLatestGenerator(CounterGenerator basis) {
    _basis = basis;
    _zipfian = new ZipfianGenerator(Integer.parseInt(_basis.lastString()));
    nextInt();
  }

  /**
   * Generate the next string in the distribution, skewed Zipfian favoring the
   * items most recently returned by the basis generator.
   */
  @Override
  public int nextInt() {
    int max = Integer.parseInt(_basis.lastString());
    int nextint = max - _zipfian.nextInt(max);
    setLastInt(nextint);
    return nextint;
  }

  public static void main(String[] args) {
    SkewedLatestGenerator gen = new SkewedLatestGenerator(new CounterGenerator(1000));
    for (int i = 0; i < Integer.parseInt(args[0]); i++) {
      System.out.println(gen.nextString());
    }
  }
}