/**
* 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.hama.examples;
import java.io.IOException;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hama.HamaConfiguration;
import org.apache.hama.bsp.BSPJob;
import org.apache.hama.bsp.BSPJobClient;
import org.apache.hama.bsp.BSPPeer;
import org.apache.hama.bsp.ClusterStatus;
import org.apache.hama.bsp.FileOutputFormat;
import org.apache.hama.bsp.NullInputFormat;
import org.apache.hama.bsp.Superstep;
import org.apache.hama.bsp.SuperstepBSP;
import org.apache.hama.bsp.TextOutputFormat;
import org.apache.hama.bsp.message.type.DoubleMessage;
/**
* This PiEstimator uses the new chainable superstep API to be fault tolerant.
*/
public class SuperstepPiEstimator {
// shared variable across multiple supersteps
private static String masterTask;
private static final Path TMP_OUTPUT = new Path("/tmp/pi-"
+ System.currentTimeMillis());
public static class PiEstimatorCalculator
extends
Superstep<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> {
private static final int iterations = 10000;
@Override
protected void setup(
BSPPeer<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> peer) {
super.setup(peer);
// Choose first as a master
masterTask = peer.getPeerName(0);
}
@Override
protected void compute(
BSPPeer<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> peer)
throws IOException {
int in = 0;
for (int i = 0; i < iterations; i++) {
double x = 2.0 * Math.random() - 1.0, y = 2.0 * Math.random() - 1.0;
if ((Math.sqrt(x * x + y * y) < 1.0)) {
in++;
}
}
double data = 4.0 * in / iterations;
DoubleMessage estimate = new DoubleMessage(peer.getPeerName(), data);
peer.send(masterTask, estimate);
}
}
protected static class PiEstimatorAggregator
extends
Superstep<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> {
@Override
protected void compute(
BSPPeer<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> peer)
throws IOException {
if (peer.getPeerName().equals(masterTask)) {
double pi = 0.0;
int numPeers = peer.getNumCurrentMessages();
DoubleMessage received;
while ((received = peer.getCurrentMessage()) != null) {
pi += received.getData();
}
pi = pi / numPeers;
peer.write(new Text("Estimated value of PI is"), new DoubleWritable(pi));
}
}
@Override
protected boolean haltComputation(
BSPPeer<NullWritable, NullWritable, Text, DoubleWritable, DoubleMessage> peer) {
return true;
}
}
private static void printOutput(HamaConfiguration conf) throws IOException {
FileSystem fs = FileSystem.get(conf);
FileStatus[] files = fs.listStatus(TMP_OUTPUT);
for (FileStatus file : files) {
if (file.getLen() > 0) {
FSDataInputStream in = fs.open(file.getPath());
IOUtils.copyBytes(in, System.out, conf, false);
in.close();
break;
}
}
fs.delete(TMP_OUTPUT, true);
}
@SuppressWarnings("unchecked")
public static void main(String[] args) throws IOException,
ClassNotFoundException, InterruptedException {
// BSP job configuration
HamaConfiguration conf = new HamaConfiguration();
BSPJob bsp = new BSPJob(conf, SuperstepBSP.class);
// Set the job name
bsp.setJobName("Fault Tolerant Pi Estimation Example");
// set our supersteps, they must be given in execution order
bsp.setSupersteps(SuperstepPiEstimator.PiEstimatorCalculator.class,
SuperstepPiEstimator.PiEstimatorAggregator.class);
bsp.setInputFormat(NullInputFormat.class);
bsp.setOutputKeyClass(Text.class);
bsp.setOutputValueClass(DoubleWritable.class);
bsp.setOutputFormat(TextOutputFormat.class);
FileOutputFormat.setOutputPath(bsp, TMP_OUTPUT);
BSPJobClient jobClient = new BSPJobClient(conf);
ClusterStatus cluster = jobClient.getClusterStatus(true);
if (args.length > 0) {
bsp.setNumBspTask(Integer.parseInt(args[0]));
} else {
// Set to maximum
bsp.setNumBspTask(cluster.getMaxTasks());
}
long startTime = System.currentTimeMillis();
if (bsp.waitForCompletion(true)) {
printOutput(conf);
System.out.println("Job Finished in "
+ (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
}
}
}