/* ----------------------------------------------------------------------- * This program - an extension of program ssq2 - simulates a single-server  * machine shop using Exponentially distributed failure times, Uniformly  * distributed service times, and a FIFO service queue.   * * Name            : ssms.c  (Single Server Machine Shop) * Authors         : Steve Park & Dave Geyer * Language        : ANSI C * Latest Revision : 9-28-98  * ----------------------------------------------------------------------- */ #include <stdio.h>#include <math.h>                                             #include "rngs.h"#define LAST    100000                  /* number of machine failures */#define START   0.0                     /* initial time               */#define M       60                      /* number of machines         */   double Exponential(double m)            /* --------------------------------------------------- * generate an Exponential random variate, use m > 0.0  * --------------------------------------------------- */{                                         return (-m * log(1.0 - Random()));     }   double Uniform(double a, double b)       /* -------------------------------------------- * generate a Uniform random variate, use a < b  * -------------------------------------------- */{                                           return (a + (b - a) * Random());    }   double GetFailure(void)       /* ------------------------------------------------  * generate the operational time until next failure  * ------------------------------------------------ */{  SelectStream(0);  return (Exponential(100.0));}   double NextFailure(double failure[], int *m)/* ----------------------------------------------------------------- * return the next failure time, and the index of the failed machine * ----------------------------------------------------------------- */{  int    i = 0;  double t = failure[0];  *m = i;  for (i = 1; i < M; i++)     if (failure[i] < t) {       t = failure[i];      *m = i;    }  return (t);}   double GetService(void)/* ------------------------------ * generate the next service time * ------------------------------ */ {  SelectStream(1);  return (Uniform(1.0, 2.0));}  int main(void){  long   index     = 0;                    /* job (machine failure) index */  double arrival   = START;                /* time of arrival (failure)   */  double delay;                            /* delay in repair  queue      */  double service;                          /* service (repair) time       */  double wait;                             /* delay + service             */  double departure = START;                /* time of service completion  */  int    m;                                /* machine index 0,1,...(M-1)  */  double failure[M];                       /* list of next failure times  */  struct {                                 /* sum of ...            */    double wait;                           /*   wait times          */    double delay;                          /*   delay times         */    double service;                        /*   service times       */    double interarrival;                   /*   interarrival times  */  } sum = {0.0, 0.0, 0.0};    PlantSeeds(123456789);  for (m = 0; m < M; m++)                   /* initial failures */    failure[m] = START + GetFailure();  while (index < LAST) {    index++;    arrival      = NextFailure(failure, &m);    if (arrival < departure)      delay      = departure - arrival;      else      delay      = 0.0;     service      = GetService();    wait         = delay + service;    departure    = arrival + wait;           /* completion of service  */    failure[m]   = departure + GetFailure(); /* next failure, machine m */    sum.wait    += wait;    sum.delay   += delay;    sum.service += service;  }  sum.interarrival = arrival - START;  printf("\nfor a pool of %d machines ", M);   printf("and %ld simulated failures\n\n", index);  printf("average interarrival time .. = %6.2f\n", sum.interarrival / index);  printf("average wait ............... = %6.2f\n", sum.wait / index);  printf("average delay .............. = %6.2f\n", sum.delay / index);  printf("average service time ....... = %6.2f\n", sum.service / index);  printf("average # in the node ...... = %6.2f\n", sum.wait / departure);  printf("average # in the queue ..... = %6.2f\n", sum.delay / departure);  printf("utilization ................ = %6.2f\n", sum.service / departure);  return (0);}