examples/pi/src/main/java/org/apache/apex/examples/pi/PiCalculateOperator.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.apex.examples.pi;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.common.util.BaseOperator;

/**
 * This operator implements Monte Carlo estimation of pi. For points randomly distributed points on
 * square circle. pi ~= Number of points in circle/Total number of points * 4.
 *
 * @since 0.3.2
 */
public class PiCalculateOperator extends BaseOperator
{
  private transient int x = -1;
  private transient int y = -1;
  private int base;
  private long inArea = 0;
  private long totalArea = 0;
  public final transient DefaultInputPort<Integer> input = new DefaultInputPort<Integer>()
  {
    @Override
    public void process(Integer tuple)
    {
      if (x == -1) {
        x = tuple;
      } else {
        y = tuple;
        if (x * x + y * y <= base) {
          inArea++;
        }
        totalArea++;
        x = y = -1;
      }
    }

  };
  public final transient DefaultOutputPort<Double> output = new DefaultOutputPort<Double>();

  @Override
  public void setup(OperatorContext context)
  {
    logger.info("inArea {} totalArea {}", inArea, totalArea);
  }

  @Override
  public void beginWindow(long windowId)
  {
  }

  @Override
  public void endWindow()
  {
    output.emit((double)inArea / totalArea * 4);
  }

  public void setBase(int num)
  {
    base = num;
  }

  public int getBase()
  {
    return base;
  }

  private static Logger logger = LoggerFactory.getLogger(PiCalculateOperator.class);
}