// EM server
//
// Usage: EMServer [port]
//
// Implements the EM algorithm for the example from section 1 of
// "Time-Recursive EM Examples", R. Perry, June 1998.
// Uses buffer size K = 1 (i.e. no buffering or pipelining).

import java.io.*;
import java.net.InetAddress;
import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.LocateRegistry;

public class EMServer extends UnicastRemoteObject implements EM
{   

  private static double c = 0;
  private static int n1 = 0;

  public EMServer() throws java.rmi.RemoteException
  {
    super();
  }
    
  public int get_b( double yK) throws RemoteException, ServerNotActiveException
  {
    System.out.println( "EMServer: get_bK(" + yK + ") called from " + this.getClientHost());

    int bK = 1;			/* initial estimate */
    double d = c;

    for( int i = 0; i < 3; ++i) {	/* 3 iterations of EM */

      /* E-step */

	d = c;

	if( bK == 1)
	  d += (yK - c)/(n1 + 1);

      /* M-step */

	bK = (d > 0) ? ((yK > d/2) ? 1 : 0) : ((yK < d/2) ? 1 : 0);
      }


    if( bK == 1) {
      ++n1;
      c = d;
    }

    System.out.println( "EMServer: c = " + c);

    return bK;
  }

  private static void createPortFile( int port) throws java.io.IOException
  {
    PrintWriter fout = new PrintWriter( new BufferedWriter( new FileWriter( "EMServer.port")));
    fout.println( InetAddress.getLocalHost().getHostName());
    fout.println( port);
    if( fout.checkError()) {
      System.err.println( "EMServer: error writing port file.");
      System.exit(1);
    }
    fout.close();
  }

  public static void main(String args[]) throws Exception
  {
    int port = 41099;

    if (args.length == 1)
      port = Integer.parseInt(args[0]);

    // Create and install the security manager
    //
    System.setSecurityManager(new RMISecurityManager());

    try {
      LocateRegistry.createRegistry(port);

      EM S = new EMServer();
      Naming.rebind("rmi://:" + port + "/EMServer", S);
 
      System.err.println("EMServer: created and bound in the registry on port " + port);

    } catch (Exception e) {

      System.err.println("EMServer: " + e);
      System.exit(1);
    }

    createPortFile( port);
  }

}