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- For the task of estimating PI:
- Each task executes its portion of the loop a number of times.
- Each task can do its work without requiring any information from the other tasks (there are no data dependencies).
- One task acts as master and collects the results.
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public class PiEstimator { private static String MASTER_TASK = "master.task."; public static class MyEstimator extends BSP { public static final Log LOG = LogFactory.getLog(MyEstimator.class); private Configuration conf; private String masterTask; private static final int iterations = 10000; public void bsp(BSPPeer bspPeer) throws IOException, KeeperException, InterruptedException { int in = 0, out = 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++; } else { out++; } } byte[] tagName = Bytes.toBytes(getName().toString()); byte[] myData = Bytes.toBytes(4.0 * (double) in / (double) iterations); BSPMessage estimate = new BSPMessage(tagName, myData); Log.info("Send a message (" + Bytes.toDouble(myData) + ") from " + bspPeer.getServerName() + " to localhost:30000"); bspPeer.send(new InetSocketAddress("localhost", 30000send(bspPeer.getAddress(masterTask), estimate); bspPeer.sync(); double pi = 0.0; BSPMessage received; while ((received = bspPeer.getCurrentMessage()) != null) { pi = (pi + Bytes.toDouble(received.getData())) / 2; } if (pi != 0.0) System.out.println("Estimated value of PI is " + pi); } @Override public Configuration getConf() { return conf; } @Override public void setConf(Configuration conf) { this.conf = conf; this.masterTask = conf.get(MASTER_TASK); } } public static void main(String[] args) throws InterruptedException, IOException { // BSP job configuration HamaConfiguration conf = new HamaConfiguration(); // Execute locally // conf.set("bsp.master.address", "local"); BSPJob bsp = new BSPJob(conf, PiEstimator.class); // Set the job name bsp.setJobName("pi estimation example"); bsp.setBspClass(MyEstimator.class); BSPJobClient jobClient = new BSPJobClient(conf); ClusterStatus cluster = jobClient.getClusterStatus(true); // Choose one as a master for (String name : cluster.getActiveGroomNames()) { conf.set(MASTER_TASK, name); break; } BSPJobClient.runJob(bsp); } } |