/*
* 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.flink.test.recordJobs.kmeans.udfs;
import java.io.Serializable;
import java.util.Iterator;
import org.apache.flink.api.java.record.functions.ReduceFunction;
import org.apache.flink.api.java.record.functions.FunctionAnnotation.ConstantFields;
import org.apache.flink.api.java.record.operators.ReduceOperator.Combinable;
import org.apache.flink.types.IntValue;
import org.apache.flink.types.Record;
import org.apache.flink.util.Collector;
/**
* Reduce PACT computes the new position (coordinate vector) of a cluster
* center. This is an average computation. Hence, Combinable is annotated
* and the combine method implemented.
*
* Output Format:
* 0: clusterID
* 1: clusterVector
*/
@Combinable
@ConstantFields(0)
public class RecomputeClusterCenter extends ReduceFunction implements Serializable {
private static final long serialVersionUID = 1L;
private final IntValue count = new IntValue();
/**
* Compute the new position (coordinate vector) of a cluster center.
*/
@Override
public void reduce(Iterator<Record> dataPoints, Collector<Record> out) {
Record next = null;
// initialize coordinate vector sum and count
CoordVector coordinates = new CoordVector();
double[] coordinateSum = null;
int count = 0;
// compute coordinate vector sum and count
while (dataPoints.hasNext()) {
next = dataPoints.next();
// get the coordinates and the count from the record
double[] thisCoords = next.getField(1, CoordVector.class).getCoordinates();
int thisCount = next.getField(2, IntValue.class).getValue();
if (coordinateSum == null) {
if (coordinates.getCoordinates() != null) {
coordinateSum = coordinates.getCoordinates();
}
else {
coordinateSum = new double[thisCoords.length];
}
}
addToCoordVector(coordinateSum, thisCoords);
count += thisCount;
}
// compute new coordinate vector (position) of cluster center
for (int i = 0; i < coordinateSum.length; i++) {
coordinateSum[i] /= count;
}
coordinates.setCoordinates(coordinateSum);
next.setField(1, coordinates);
next.setNull(2);
// emit new position of cluster center
out.collect(next);
}
/**
* Computes a pre-aggregated average value of a coordinate vector.
*/
@Override
public void combine(Iterator<Record> dataPoints, Collector<Record> out) {
Record next = null;
// initialize coordinate vector sum and count
CoordVector coordinates = new CoordVector();
double[] coordinateSum = null;
int count = 0;
// compute coordinate vector sum and count
while (dataPoints.hasNext()) {
next = dataPoints.next();
// get the coordinates and the count from the record
double[] thisCoords = next.getField(1, CoordVector.class).getCoordinates();
int thisCount = next.getField(2, IntValue.class).getValue();
if (coordinateSum == null) {
if (coordinates.getCoordinates() != null) {
coordinateSum = coordinates.getCoordinates();
}
else {
coordinateSum = new double[thisCoords.length];
}
}
addToCoordVector(coordinateSum, thisCoords);
count += thisCount;
}
coordinates.setCoordinates(coordinateSum);
this.count.setValue(count);
next.setField(1, coordinates);
next.setField(2, this.count);
// emit partial sum and partial count for average computation
out.collect(next);
}
/**
* Adds two coordinate vectors by summing up each of their coordinates.
*
* @param cvToAddTo
* The coordinate vector to which the other vector is added.
* This vector is returned.
* @param cvToBeAdded
* The coordinate vector which is added to the other vector.
* This vector is not modified.
*/
private void addToCoordVector(double[] cvToAddTo, double[] cvToBeAdded) {
// check if both vectors have same length
if (cvToAddTo.length != cvToBeAdded.length) {
throw new IllegalArgumentException("The given coordinate vectors are not of equal length.");
}
// sum coordinate vectors coordinate-wise
for (int i = 0; i < cvToAddTo.length; i++) {
cvToAddTo[i] += cvToBeAdded[i];
}
}
}