library/src/main/java/com/datatorrent/lib/algo/MergeSortNumber.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.algo;

import com.datatorrent.api.annotation.OperatorAnnotation;
import java.util.ArrayList;

/**
 * This unifier takes sorted lists of tuples each window and merges them into one large sorted list at the end of each window.
 * <p>
 * Incoming sorted list is merged into already existing sorted list. The input list is expected to be sorted. <b>
 * At the end of the window, merged sorted list is emitted on sort output port. <br>
 * <br>
 * <b>Notes : </b> <br>
 * Get unifier instance must return instance of sub class itself, since merge operator
 * id unifier on output port. <br>
 * <br>
 *  <b>StateFull : Yes</b>, Sorted listed are merged over application window can be > 1. <br>
 *  <b>Partitions : Yes</b>, Operator itself is used as unfier on output port.
 * <br>
 * <b>Ports</b>:<br>
 * <b>data</b>: expects ArrayList&lt;K&gt;<br>
 * <b>sort</b>: emits ArrayList&lt;K&gt;<br>
 * <br>
 * <b>Abstract Methods: </b><br>
 * 1. compare : K type value compare criteria for sort.
 * 2. getUnifierInstance : Get unifier operator instance for output port, (must return self instance).
 * </p>
 * @displayName Merge Sorted Lists (Number)
 * @category Algorithmic
 * @tags rank, numeric
 *
 * @since 0.3.3
 */
@OperatorAnnotation(partitionable = true)
public class MergeSortNumber<V extends Number> extends MergeSort<V>
{
	/**
	 * Ascending/Desending flag;
	 */
	private boolean ascending = true;

	/**
	 * sort function.
	 */
	@SuppressWarnings("unchecked")
	public  V[] compare(V val1, V val2) {
		V[] result =  (V[]) new Number[2];
		if (ascending) {
  		if (val1.doubleValue() < val2.doubleValue()) {
  			result[0] = val1;
  			result[1] = val2;
  		} else {
  			result[0] = val2;
  			result[1] = val1;
  		}
		} else {
  		if (val1.doubleValue() < val2.doubleValue()) {
  			result[0] = val2;
  			result[1] = val1;
  		} else {
  			result[0] = val1;
  			result[1] = val2;
  		}
		}
		return result;
	}

	/**
	 *  Merge class itself is unifier.
	 */
	public Unifier<ArrayList<V>> getUnifierInstance() {
		return new MergeSortNumber<V>();
	}

	public boolean isAscending()
	{
		return ascending;
	}

	public void setAscending(boolean ascending)
	{
		this.ascending = ascending;
	}
}