library/src/main/java/com/datatorrent/lib/math/Average.java

/*
 * Copyright (c) 2013 DataTorrent, 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.
 */
package com.datatorrent.lib.math;

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.annotation.InputPortFieldAnnotation;
import com.datatorrent.api.annotation.OutputPortFieldAnnotation;
import com.datatorrent.lib.util.BaseNumberValueOperator;

/**
 *
 * Emits the average of values at the end of window.
 * <p>
 * This is an end window operator. This can not be partitioned. Partitioning
 * this will yield incorrect result.<br>
 * <b>Ports</b>:<br>
 * <b>data</b>: expects V extends Number<br>
 * <b>average</b>: emits V extends Number<br>
 * <br>
 * <br>
 * <b>Properties</b>: None<br>
 * <b>Specific compile time checks</b>: None<br>
 * <b>Specific run time checks</b>: None<br>
 * <p>
 * @displayname: Average
 * @category: math
 * @tags: average, numeric, end window
 * @since 0.3.3
 */
public class Average<V extends Number> extends BaseNumberValueOperator<V>
{
	/**
	 * Input port that takes a number.
	 */
	@InputPortFieldAnnotation(name = "data")
	public final transient DefaultInputPort<V> data = new DefaultInputPort<V>()
	{
		/**
		 * Computes sum and count with each tuple
		 */
		@Override
		public void process(V tuple)
		{
			sums += tuple.doubleValue();
			counts++;
		}
	};

	/**
	 * Output port that emits average as a number.
	 */
	@OutputPortFieldAnnotation(name = "average")
	public final transient DefaultOutputPort<V> average = new DefaultOutputPort<V>();

	protected double sums = 0;
	protected long counts = 0;

	/**
	 * Emit average.
	 */
	@Override
	public void endWindow()
	{
		// May want to send out only if count != 0
		if (counts != 0) {
			average.emit(getAverage());
		}
		sums = 0;
		counts = 0;
	}

	/**
	 * Calculate average based on number type.
	 */
	@SuppressWarnings("unchecked")
	public V getAverage()
	{
		if (counts == 0) {
			return null;
		}
		V num = getValue(sums);
		Number val;
		switch (getType()) {
			case DOUBLE:
				val = new Double(num.doubleValue() / counts);
				break;
			case INTEGER:
				int icount = (int) (num.intValue() / counts);
				val = new Integer(icount);
				break;
			case FLOAT:
				val = new Float(num.floatValue() / counts);
				break;
			case LONG:
				val = new Long(num.longValue() / counts);
				break;
			case SHORT:
				short scount = (short) (num.shortValue() / counts);
				val = new Short(scount);
				break;
			default:
				val = new Double(num.doubleValue() / counts);
				break;
		}
		return (V) val;
	}
}