/*
 * LoadBalanceManager.java
 *
 * Load Balance Manager data and operations for stochastic selection
 * of servers.
 *
 *  Created by: Arthur L. Blais
 *              Visteon/Ford Microelectronics Inc.
 *              Colorado Springs, CO
 *
 *  Date: Fri Jan  7 11:02:31 MST 2000
 *  Wed Mar 29 07:21:05 MST 2000: add random selection for adversarial tests
 *
 *
 ****************************************************************************
 *
 *   Class Methods
 *
 *
 ****************************************************************************
 */
 
import java.util.Random;

public class LoadBalanceManager {

  int id;                                // id number
  int server[];                          // request count for each server
  int lastServer = 0;                    // last server round robin selection
  int requestCount = 0;                  // current total request count
  int serverCount;                       // number of servers
  int managerType;                       // LBM type, 0 = stochastic,1 = random

  // Pseudo-Random Variate Seeds
  private static long seed = 98391;
  // random number instances
  private static Random randNumber;      // = new Random( seed );

  public LoadBalanceManager( int n, int s, int t ) {

    id = n;
    server = new int[ s ];
    serverCount = s;
    managerType = t;
    

    for ( int i = 0; i < server.length; i++ ) {
       server[i] = 0;
    }

    randNumber = new Random( seed + id );
  }

  /**
   * getId
   */
  int getId() {
    return id;
  }  

  /**
   * requestComplete
   */
  void requestComplete( int s ) {
 
     requestCount--;
     server[s]--;
  }

  /**
   * nextServer
   *
   *  selects a server to submit a request to
   *  if request count is zero return the first server
   *  else select a server by calculating a probability distribution
   *       based on the current number of server reqeusts counted
   *       (selected) by this lbm.
   */
  int nextServer() {

    int nextServer;

    if ( managerType == 1 ) {
      // random manager
      nextServer = Math.abs( randNumber.nextInt() ) % serverCount;
      server[nextServer]++;

      return( nextServer );  
    }
    
    int i;
    nextServer = 0;
    long product = 1;
    long sum = 0;
    double upperLimit;
    double randomNumber = randNumber.nextDouble();

    long temp[] = new long[ server.length ];

    // add one to the each server's totals
    // and calculate the product
    for ( i = 0; i < server.length; i++ ) {
       temp[i] = server[i] + 1;
       product *= temp[i];
    }
 
    // divide the product by the temp server count
    // and sum the new value
    for ( i = 0; i < server.length; i++ ) {
       temp[i] = product / temp[i];
       sum += temp[i];
    }

    // divide each temp server count by the sum and
    // find the next server with the random variate
    i = 0;
    upperLimit = ( double ) temp[i] / ( double ) sum;

    while ( upperLimit < randomNumber ) { 
        i++;
        upperLimit += ( double ) temp[i] / ( double ) sum;
    }

    nextServer = i;
       
    server[nextServer]++;
    requestCount++;

    return( nextServer );  
  }

}