/* ------------------------------------------------------------------------- * This program is a next-event simulation of a multi-server, single-queue * service node.  The service node is assumed to be initially idle, no * arrivals are permitted after the terminal time STOP and the node is then * purged by processing any remaining jobs. * * Name              : Msq.java (Multi-Server Queue) * 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 MsqT {  double current;                   /* current time                       */  double next;                      /* next (most imminent) event time    */}class MsqSum {                      /* accumulated sums of                */  double service;                   /*   service times                    */  long   served;                    /*   number served                    */}class MsqEvent{                     /* the next-event list    */  double t;                         /*   next event time      */  int    x;                         /*   event status, 0 or 1 */}class Msq {  static double START   = 0.0;            /* initial (open the door)        */  static double STOP    = 20000.0;        /* terminal (close the door) time */  static int    SERVERS = 4;              /* number of servers              */  static double sarrival = START;              public static void main(String[] args) {          long   number = 0;             /* number in the node                 */    int    e;                      /* next event index                   */    int    s;                      /* server index                       */    long   index  = 0;             /* used to count processed jobs       */    double area   = 0.0;           /* time integrated number in the node */    double service;        Msq m = new Msq();    Rngs r = new Rngs();    r.plantSeeds(0);    MsqEvent [] event = new MsqEvent [SERVERS + 1];    MsqSum [] sum = new MsqSum [SERVERS + 1];    for (s = 0; s < SERVERS + 1; s++) {      event[s] = new MsqEvent();      sum [s]  = new MsqSum();    }        MsqT t = new MsqT();    t.current    = START;    event[0].t   = m.getArrival(r);    event[0].x   = 1;    for (s = 1; s <= SERVERS; s++) {      event[s].t     = START;          /* this value is arbitrary because */      event[s].x     = 0;              /* all servers are initially idle  */      sum[s].service = 0.0;      sum[s].served  = 0;    }    while ((event[0].x != 0) || (number != 0)) {      e         = m.nextEvent(event);                /* next event index */      t.next    = event[e].t;                        /* next event time  */      area     += (t.next - t.current) * number;     /* update integral  */      t.current = t.next;                            /* advance the clock*/      if (e == 0) {                                  /* process an arrival*/        number++;        event[0].t        = m.getArrival(r);        if (event[0].t > STOP)          event[0].x      = 0;        if (number <= SERVERS) {          service         = m.getService(r);          s               = m.findOne(event);          sum[s].service += service;          sum[s].served++;          event[s].t      = t.current + service;          event[s].x      = 1;        }      }      else {                                         /* process a departure */        index++;                                     /* from server s       */        number--;        s                 = e;        if (number >= SERVERS) {          service         = m.getService(r);          sum[s].service += service;          sum[s].served++;          event[s].t      = t.current + service;        }        else          event[s].x      = 0;      }    }    DecimalFormat f = new DecimalFormat("###0.00");    DecimalFormat g = new DecimalFormat("###0.000");    System.out.println("\nfor " + index + " jobs the service node statistics are:\n");    System.out.println("  avg interarrivals .. =   " + f.format(event[0].t / index));    System.out.println("  avg wait ........... =   " + f.format(area / index));    System.out.println("  avg # in node ...... =   " + f.format(area / t.current));    for (s = 1; s <= SERVERS; s++)          /* adjust area to calculate */       area -= sum[s].service;              /* averages for the queue   */    System.out.println("  avg delay .......... =   " + f.format(area / index));    System.out.println("  avg # in queue ..... =   " + f.format(area / t.current));    System.out.println("\nthe server statistics are:\n");    System.out.println("    server     utilization     avg service      share");    for (s = 1; s <= SERVERS; s++) {      System.out.print("       " + s + "          " + g.format(sum[s].service / t.current) + "            ");      System.out.println(f.format(sum[s].service / sum[s].served) + "         " + g.format(sum[s].served / (double)index));    }          System.out.println("");  }    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 a 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 1/6 * ------------------------------ */    r.selectStream(1);    return (uniform(2.0, 10.0, r));  }  int nextEvent(MsqEvent [] event) {/* --------------------------------------- * return the index of the next event type * --------------------------------------- */    int e;    int i = 0;    while (event[i].x == 0)       /* find the index of the first 'active' */      i++;                        /* element in the event list            */    e = i;    while (i < SERVERS) {         /* now, check the others to find which  */      i++;                        /* event type is most imminent          */      if ((event[i].x == 1) && (event[i].t < event[e].t))        e = i;    }    return (e);  }  int findOne(MsqEvent [] event) {/* ----------------------------------------------------- * return the index of the available server idle longest * ----------------------------------------------------- */    int s;    int i = 1;    while (event[i].x == 1)       /* find the index of the first available */      i++;                        /* (idle) server                         */    s = i;    while (i < SERVERS) {         /* now, check the others to find which   */      i++;                        /* has been idle longest                 */      if ((event[i].x == 0) && (event[i].t < event[s].t))        s = i;    }    return (s);  }   }