HistogramWithStats.java

package com.splout.db.benchmark;

/*
 * #%L
 * Splout SQL commons
 * %%
 * Copyright (C) 2012 Datasalt Systems S.L.
 * %%
 * 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.
 * #L%
 */

/**
 * A {@link PositiveHistogram} but that also keeps average, stdev, min and max values.
 */
public class HistogramWithStats extends PositiveHistogram {

  private double squares = 0;
  private double accum = 0;
  private double min = Double.MAX_VALUE;
  private double max = Double.MIN_VALUE;

  public HistogramWithStats(int bits, double initialUpperLimit) {
    super(bits, initialUpperLimit);
  }

  public HistogramWithStats(int bits) {
    // Histogram upper limit is enforced by the number of bits.
    // This way, ranges in the histogram will always be integers.
    this(bits, (int) Math.pow(2, bits - 1));
  }

  public HistogramWithStats() {
    super(8, 1);
  }

  /*
   * Deep copy constructor
   */
  public HistogramWithStats(HistogramWithStats copy) {
    super(1, copy.upperLimit);
    buckets = new int[copy.buckets.length];
    for (int i = 0; i < copy.buckets.length; i++) {
      this.buckets[i] = copy.buckets[i];
    }
    count = copy.count;
    squares = copy.squares;
    accum = copy.accum;
    min = copy.min;
    max = copy.max;
  }

  @Override
  public synchronized void add(double value) {
    super.add(value);

    accum += value;
    squares += (value * value);

    min = Math.min(min, value);
    max = Math.max(max, value);
  }

  public synchronized double getAverage() {
    return accum / getCount();
  }

  public synchronized double getAccum() {
    return accum;
  }

  /**
   * Returns the stdev.
   */
  public synchronized double getStdev() {
    return Math.sqrt((squares / getCount()) - Math.pow(getAverage(), 2));
  }

  /**
   * Return the maximun value
   */
  public synchronized double getMax() {
    return max;
  }

  /**
   * Return the minimun value
   */
  public synchronized double getMin() {
    return min;
  }
}