public static void main(String[] args) {
// Handle invalid arguments..
if (args.length < 2) {
System.out.println("Usage: ConvexHull arg1 arg2");
System.out.println("arg1: input dataset A file path [points]");
System.out.println("arg2: output file name and path");
System.exit(1);
}
// Creating and setting sparkconf
SparkConf sparkConf = new SparkConf().setAppName("Group3-edu.asu.cse512.ConvexHull");
JavaSparkContext sc = new JavaSparkContext(sparkConf);
// Adding external jars
// sc.addJar("lib/jts-1.13.jar");
JavaRDD<String> lines = sc.textFile(args[0]);
// Using mapPartitions function to find convex hull points in distributed environment
JavaRDD<Coordinate> hullPointsRDD = lines.mapPartitions(new ConvexH());
List<Coordinate> hullPointsList = hullPointsRDD.collect();
Coordinate[] inputArray = new Coordinate[hullPointsList.size()];
int j = 0;
for (Coordinate c : hullPointsList) {
inputArray[j] = c;
j++;
}
// Finding convex hull points on the final subset of points retrieved from distributed
// environment
GeometryFactory geoFactory1 = new GeometryFactory();
MultiPoint mPoint1 = geoFactory1.createMultiPoint(inputArray);
Geometry geo1 = mPoint1.convexHull();
Coordinate[] convexHullResult = geo1.getCoordinates();
int length = convexHullResult.length;
Coordinate[] convexHullFinalResult = Arrays.copyOf(convexHullResult, length - 1);
Arrays.sort(convexHullFinalResult);
// Converting the list of coordinates into Coordinate RDD
JavaRDD<Coordinate> convexHullResultRDD =
sc.parallelize(Arrays.asList(convexHullFinalResult), 1);
JavaRDD<String> convexHullResultString =
convexHullResultRDD
.repartition(1)
.map(
new Function<Coordinate, String>() {
public String call(Coordinate hullPoint) throws Exception {
return hullPoint.x + "," + hullPoint.y;
}
});
// Save the String RDD into text file. Using repartition(1) to preserve the order of coordinates
convexHullResultString.repartition(1).saveAsTextFile(args[1]);
}
public Iterable<Coordinate> call(Iterator<String> coordinatesIterator) throws Exception {
// TODO Auto-generated method stub
List<Coordinate> coorList = new ArrayList<Coordinate>();
// Retrieving points from JavaRDD<String> and storing it in a list
while (coordinatesIterator.hasNext()) {
String[] temp = coordinatesIterator.next().split(",");
coorList.add(new Coordinate(Double.parseDouble(temp[0]), Double.parseDouble(temp[1])));
}
Coordinate[] coorArray = new Coordinate[coorList.size()];
int i = 0;
for (Coordinate c : coorList) {
coorArray[i] = c;
i++;
}
// Using Geometry class of JTS library to find convex hull points
GeometryFactory geoFactory = new GeometryFactory();
MultiPoint mPoint = geoFactory.createMultiPoint(coorArray);
Geometry geo = mPoint.convexHull();
Coordinate[] convexResult = geo.getCoordinates();
return Arrays.asList(convexResult);
}