/* ------------------------------------------------------------------------- * This program is a next-event simulation of a single-server FIFO service * node using Exponentially distributed interarrival times and Uniformly * distributed service times (i.e., a M/U/1 queue).  The service node is * assumed to be initially idle, no arrivals are permitted after the * terminal time STOP, and the service node is then purged by processing any * remaining jobs in the service node. * * Name              : Ssq3.java  (Single Server Queue, version 3) * Authors           : Steve Park & Dave Geyer * Translated by     : Jun Wang * Language          : Java * Latest Revision   : 6-16-06 * -------------------------------------------------------------------------  */import java.io.*;import java.lang.*;import java.text.*;class Ssq3Area {                  double node;                    /* time integrated number in the node  */  double queue;                   /* time integrated number in the queue */  double service;                 /* time integrated number in service   */  void initAreaParas() {    node = 0.0;    queue = 0.0;    service = 0.0;  }}class Ssq3T {  double arrival;                 /* next arrival time                   */  double completion;              /* next completion time                */  double current;                 /* current time                        */  double next;                    /* next (most imminent) event time     */  double last;                    /* last arrival time                   */}class Ssq3 {  static double START = 0.0;              /* initial time                   */  static double STOP  = 20000.0;          /* terminal (close the door) time */  static double INFINITY = 100.0 * STOP;  /* must be much larger than STOP  */    static double sarrival = START;              /* Why did I do this?       */  public static void main(String[] args) {        long index  = 0;                  /* used to count departed jobs         */    long number = 0;                  /* number in the node                  */    Ssq3 s = new Ssq3();        Rngs r = new Rngs();    r.plantSeeds(123456789);    Ssq3T t      = new Ssq3T();    t.current    = START;           /* set the clock                         */    t.arrival    = s.getArrival(r); /* schedule the first arrival            */    t.completion = INFINITY;        /* the first event can't be a completion */    Ssq3Area area = new Ssq3Area();    area.initAreaParas();    while ((t.arrival < STOP) || (number > 0)) {      t.next          = Math.min(t.arrival, t.completion);  /* next event time   */      if (number > 0)  {                               /* update integrals  */        area.node    += (t.next - t.current) * number;        area.queue   += (t.next - t.current) * (number - 1);        area.service += (t.next - t.current);      }      t.current       = t.next;                    /* advance the clock */      if (t.current == t.arrival)  {               /* process an arrival */        number++;        t.arrival     = s.getArrival(r);        if (t.arrival > STOP)  {          t.last      = t.current;          t.arrival   = INFINITY;        }        if (number == 1)          t.completion = t.current + s.getService(r);      }      else {                                        /* process a completion */        index++;        number--;        if (number > 0)          t.completion = t.current + s.getService(r);        else          t.completion = INFINITY;      }    }    DecimalFormat f = new DecimalFormat("###0.00");    System.out.println("\nfor " + index + " jobs");    System.out.println("   average interarrival time =   " + f.format(t.last / index));    System.out.println("   average wait ............ =   " + f.format(area.node / index));    System.out.println("   average delay ........... =   " + f.format(area.queue / index));    System.out.println("   average service time .... =   " + f.format(area.service / index));    System.out.println("   average # in the node ... =   " + f.format(area.node / t.current));    System.out.println("   average # in the queue .. =   " + f.format(area.queue / t.current));    System.out.println("   utilization ............. =   " + f.format(area.service / t.current));  }  double exponential(double m, Rngs r) {/* --------------------------------------------------- * generate an Exponential random variate, use m > 0.0 * --------------------------------------------------- */    return (-m * Math.log(1.0 - r.random()));  }  double uniform(double a, double b, Rngs r) {/* ------------------------------------------------ * generate an Uniform random variate, use a < b * ------------------------------------------------ */    return (a + (b - a) * r.random());  }   double getArrival(Rngs r) {/* --------------------------------------------- * generate the next arrival time, with rate 1/2 * --------------------------------------------- */    r. selectStream(0);    sarrival += exponential(2.0, r);    return (sarrival);  }  double getService(Rngs r) {/* -------------------------------------------- * generate the next service time with rate 2/3 * -------------------------------------------- */    r. selectStream(1);    return (uniform(1.0, 2.0, r));  }}