//===================================================== file = mm1_csim.c =====
//=  A CSIM simulation of an M/M/1 queueing system                            =
//=============================================================================
//=  Notes: 1) Values for lambda and mu are set in the main program           =
//=         2) Computes theoretical results for comparison                    =
//=---------------------------------------------------------------------------=
//= Example execution:                                                        =
//=                                                                           =
//=   *** BEGIN SIMULATION ***                                                =
//=   =============================================================           =
//=   ==     *** CSIM M/M/1 queueing system simulation ***       ==           =
//=   =============================================================           =
//=   = Lambda   =  1.000 cust/sec                                            =
//=   = Mu       =  3.000 cust/sec                                            =
//=   =============================================================           =
//=   = Total CPU time     =  0.411 sec                                       =
//=   = Total sim time     = 100000.000 sec                                   =
//=   = Total completions  = 100173 cust                                      =
//=   =------------------------------------------------------------           =
//=   = >>> Simulation results                                    -           =
//=   =------------------------------------------------------------           =
//=   = Utilization        = 33.224 %                                         =
//=   = Mean num in system =  0.499 cust                                      =
//=   = Mean response time =  0.498 sec                                       =
//=   = Mean service time  =  0.332 sec                                       =
//=   = Mean throughput    =  1.002 cust/sec                                  =
//=   =------------------------------------------------------------           =
//=   = >>> Theoretical results                                   -           =
//=   =------------------------------------------------------------           =
//=   = Utilization        = 33.333 %                                         =
//=   = Mean num in system =  0.500 cust                                      =
//=   = Mean response time =  0.500 sec                                       =
//=   = Mean service time  =  0.333 sec                                       =
//=   = Mean throughput    =  1.000 cust/sec                                  =
//=   =============================================================           =
//=   *** END SIMULATION ***                                                  =
//=---------------------------------------------------------------------------=
//=  Build: standard CSIM build                                               =
//=---------------------------------------------------------------------------=
//=  Execute: mm1_csim                                                        =
//=---------------------------------------------------------------------------=
//=  Author: Ken Christensen                                                  =
//=          University of South Florida                                      =
//=          WWW: http://www.csee.usf.edu/~christen                           =
//=          Email: christen@csee.usf.edu                                     =
//=---------------------------------------------------------------------------=
//=  History: KJC (02/27/97) - Genesis                                        =
//=           KJC (01/27/04) - Added documentation and localized some vars    =
//=============================================================================
//----- Includes --------------------------------------------------------------
#include <stdio.h>      // Needed for printf()
#include "csim.h"       // Needed for CSIM18 stuff

//----- Defines ---------------------------------------------------------------
#define SIM_TIME 1.0e5  // Total simulation time in seconds

//----- Globals ---------------------------------------------------------------
FACILITY Server;        // Declaration of CSIM Server facility

//----- Prototypes ------------------------------------------------------------
void generate(double lambda, double mu);  // Customer generator
void queue1(double service_time);         // Single server queue

//=============================================================================
//==  Main program                                                           ==
//=============================================================================
void sim(void)
{
  double   lambda;      // Mean arrival rate (cust/sec)
  double   mu;          // Mean service rate (cust/sec)
  double   rho;         // Theoretical utilization

  // Create the simulation
  create("sim");

  // CSIM initializations
  Server = facility("Server");

  // Parameter initializations
  lambda = 1.0;
  mu = 3.0;

  // Output begin-of-simulation banner
  printf("*** BEGIN SIMULATION *** \n");

  // Initiate generate function and hold for SIM_TIME
  generate(lambda, mu);
  hold(SIM_TIME);

  // Compute theoretical utilization
  rho = lambda / mu;

  // Output results
  printf("============================================================= \n");
  printf("==     *** CSIM M/M/1 queueing system simulation ***       == \n");
  printf("============================================================= \n");
  printf("= Lambda   = %6.3f cust/sec   \n", lambda);
  printf("= Mu       = %6.3f cust/sec   \n", mu);
  printf("============================================================= \n");
  printf("= Total CPU time     = %6.3f sec      \n", cputime());
  printf("= Total sim time     = %6.3f sec      \n", clock);
  printf("= Total completions  = %ld cust       \n", completions(Server));
  printf("=------------------------------------------------------------ \n");
  printf("= >>> Simulation results                                    - \n");
  printf("=------------------------------------------------------------ \n");
  printf("= Utilization        = %6.3f %%       \n", 100.0 * util(Server));
  printf("= Mean num in system = %6.3f cust     \n", qlen(Server));
  printf("= Mean response time = %6.3f sec      \n", resp(Server));
  printf("= Mean service time  = %6.3f sec      \n", serv(Server));
  printf("= Mean throughput    = %6.3f cust/sec \n", tput(Server));
  printf("=------------------------------------------------------------ \n");
  printf("= >>> Theoretical results                                   - \n");
  printf("=------------------------------------------------------------ \n");
  printf("= Utilization        = %6.3f %%       \n", 100.0 * rho);
  printf("= Mean num in system = %6.3f cust     \n", rho / (1.0 - rho));
  printf("= Mean response time = %6.3f sec      \n", (1.0 / mu) / (1.0 - rho));
  printf("= Mean service time  = %6.3f sec      \n", (1.0 / mu));
  printf("= Mean throughput    = %6.3f cust/sec \n", lambda);
  printf("============================================================= \n");

  // Output end-of-simulation banner
  printf("*** END SIMULATION *** \n");
}

//=============================================================================
//==  Function to generate Poisson customers                                 ==
//=============================================================================
void generate(double lambda, double mu)
{
  double   interarrival_time;    // Interarrival time to next send
  double   service_time;         // Service time for this customer

  create("generate");

  // Loop forever to create customers
  while(1)
  {
    // Pull an interarrival time and hold for it
    interarrival_time = exponential(1.0 / lambda);
    hold(interarrival_time);

    // Pull a service time and then send the customer to the queue
    service_time = exponential(1.0 / mu);
    queue1(service_time);
  }
}

//=============================================================================
//==  Function for single server queue                                       ==
//=============================================================================
void queue1(double service_time)
{
  create("queue1");

  // Reserve, hold, and release server
  reserve(Server);
  hold(service_time);
  release(Server);
}