//======================================================= file = tandem.c =====
//=  Simulation model of a tandem queue                                       =
//=============================================================================
//=  Notes: This program is the solution for an in-class example for          =
//=         Simulation Spring 2005.                                           =
//=---------------------------------------------------------------------------=
//=  Build: Standard SMPL build                                               =
//=---------------------------------------------------------------------------=
//=  History: KJC (03/01/05) - Genesis                                        =
//=============================================================================
//----- Include files ---------------------------------------------------------
#include "smpl.h"       // Needed for SMPL
#include <stdio.h>      // Needed for printf()
#include <assert.h>     // Needed for assert macro
#include <stdlib.h>     // Needed for atof()

//===== Main program ==========================================================
void main(int argc, char *argv[])
{
  real Ta;              // Mean interarrival time
  real Ts_1 = 10;       // Mean service time for server #1
  real Ts_2 = 10;       // Mean service time for server #2
  real te;              // Total simulation time
  int customer = 1;     // Customer id (always '1' for this simulation)
  int event;            // Event
  int server1;          // Handle for server #1 facility
  int server2;          // Handle for server #2 facility

  // Initialize SMPL subsystem
  smpl(0, "Tandem queue model");

  // Output usage
  if (argc != 3)
  {
    printf("Usage: tandem Ta te                                            \n");
    printf("       where Ta is mean interarrival time                      \n");
    printf("             te is the simulation time                         \n");
    return;
  }

  // Parse input arguments and assert the values
  Ta = atof(argv[1]);
  te = atof(argv[2]);
  assert(Ta > 0.0);
  assert(te > 0.0);

  // Initialize server facilities
  server1 = facility("server #1", 1);
  server2 = facility("server #2", 1);

  // Schedule arrival event at time 0 to kick-off simulation
  schedule(1, 0.0, customer);

  // Loop while simulation time is less than te
  while (time() < te)
  {
    // "Cause" the next event on the event list
    cause(&event,&customer);

    // Process the event
    switch(event)
    {
      case 1:  // *** Arrival
        schedule(1, expntl(Ta), customer);
        schedule(2, 0.0, customer);
        break;

      case 2:  // *** Request server #1
        if (request(server1, customer, 0) == 0)
          schedule(3, Ts_1, customer);
        break;

      case 3:  // *** Release server #1 and schedule next queue arrival
        release(server1, customer);
        schedule(4, 0.0, customer);
        break;

      case 4:  // *** Request server #2
        if (request(server2, customer, 0) == 0)
          schedule(5, Ts_2, customer);
        break;

      case 5:  // *** Release server #2
        release(server2, customer);
        break;

      default: // *** This is the error case
        break;
    }
  }

  // Output custom report
  printf("---------------------------------------------------- \n");
  printf("- Mean interarrival time              = %f millisec \n",
    Ta);
  printf("---------------------------------------------------- \n");
  printf("- Utilization for server #1           = %f %% \n",
    100.0 * U(server1));
  printf("- Mean number in system for server #1 = %f           \n",
    Lq(server1) + U(server1));
  printf("- Mean delay server #1                = %f millisec  \n",
    Ta * (Lq(server1) + U(server1)));
  printf("- Utilization for server #2           = %f %%        \n",
    100.0 * U(server2));
  printf("- Mean number in system for server #2 = %f           \n",
    Lq(server2) + U(server2));
  printf("- Mean delay server #2                = %f millisec  \n",
    Ta * (Lq(server2) + U(server2)));
  printf("---------------------------------------------------- \n");
}