library/src/main/java/com/datatorrent/lib/util/UnifierSumNumber.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.util;

import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.Operator.Unifier;

/**
 * This unifier consumes numbers, and emits their sum at the end of each application window.
 * <p>
 * This unifier uses round robin partitioning.
 * </p>
 * @displayName Unifier Sum Number
 * @category Algorithmic
 * @tags numeric
 * @since 0.3.2
 */
public class UnifierSumNumber<V extends Number> extends BaseNumberValueOperator<V> implements Unifier<V>
{
  private Double result = 0.0;
  private boolean doEmit = false;
  /**
   * This is the output port which emits a sum.
   */
  public final transient DefaultOutputPort<V> mergedport = new DefaultOutputPort<V>();

  /**
   * Adds tuple with result so far
   *
   * @param tuple incoming tuple from a partition
   */
  @Override
  public void process(V tuple)
  {
    result += tuple.doubleValue();
    doEmit = true;
  }

  /**
   * emits the result, and resets it
   */
  @Override
  public void endWindow()
  {
    if (doEmit) {
      mergedport.emit(getValue(result));
      result = 0.0;
      doEmit = false;
    }
  }

  /**
   * a no-op
   *
   * @param context
   */
  @Override
  public void setup(OperatorContext context)
  {
  }

  /**
   * a noop
   */
  @Override
  public void teardown()
  {
  }
}