//===================================================== file = as3_4sol.c =====
//=  A simulation of dual queues with a single source                         =
//=============================================================================
//=  Notes:                                                                   =
//=    This program is the solution for assignment #4 for Computer            =
//=    Simulation, Spring 1999.  See the handout for the specific             =
//=    requirements for this program.                                         =
//=---------------------------------------------------------------------------=
//=  Build: bcc32 as3_4sol.c smpl.c bmeans.c rand.c                           =
//=---------------------------------------------------------------------------=
//=  History:  KJC (02/13/99) - Genesis                                       =
//=============================================================================
//----- Include files ---------------------------------------------------------
#include <stdio.h>      // Needed for printf()
#include "smpl.h"       // Needed for SMPL

//----- Defines ---------------------------------------------------------------
#define BALANCE_MODE         2  // 0 = random balance, 1 = round robin,
                                // 2 = shortest queue

#define SIM_TIME         1.0e5  // Total time to run simulation
#define ARRIVAL_TIME  1.0 / 18  // Mean time between customer arrivals (sec)
#define SERV_TIME_1   1.0 / 10  // Mean service time (sec) for server #1
#define SERV_TIME_2   1.0 / 10  // Mean service time (sec) for server #2

//===== Main program ==========================================================
void main(void)
{
  real Ta = ARRIVAL_TIME;  // Mean interarrival time (sec)
  real Ts_1 = SERV_TIME_1; // Mean service time (sec) for server #1
  real Ts_2 = SERV_TIME_2; // Mean service time (sec) for server #2
  real te = SIM_TIME;      // Total simulation time
  int  balance_mode;       // Balance mode (0, 1, or 2)
  int  index = 0;          // Server index for round robin balancing
  int  customer = 1;       // Customer id (always '1' for this simulation)
  int  event;              // Event
  int  server_1;           // Handle for server facility #1
  int  server_2;           // Handle for server facility #2
  long count_1;            // Number of customers served by facility #1
  long count_2;            // Number of customers served by facility #2
  int  queue_len_1;        // Queue length #1 (including in-service customer)
  int  queue_len_2;        // Queue length #2 (including in-service customer)
  real wait_1;             // Mean system wait for facility #1
  real wait_2;             // Mean system wait for facility #2
  real mean_wait;          // Mean wait for an arbitrary customer

  // Initialize balancing mode
  balance_mode = BALANCE_MODE;

  // Initialize SMPL subsystem
  smpl(0, "Dual Queue Simulation");

  // Initialize server facilities (two single servers)
  server_1 = facility("server #1", 1);
  server_2 = facility("server #2", 1);

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

  // Initialize customer counters
  count_1 = count_2 = 0;

  // 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
        if (balance_mode == 0)
        {
          if (ranf() < 0.50)
            schedule(2, 0.0, customer);
          else
            schedule(4, 0.0, customer);
        }
        if (balance_mode == 1)
        {
          index++;
          if (index == 2) index = 0;
          if (index == 0)
            schedule(2, 0.0, customer);
          else
            schedule(4, 0.0, customer);
        }
        if (balance_mode == 2)
        {
          queue_len_1 = inq(server_1) + status(server_1);
          queue_len_2 = inq(server_2) + status(server_2);

          if (queue_len_1 < queue_len_2)
            schedule(2, 0.0, customer);
          if (queue_len_1 > queue_len_2)
            schedule(4, 0.0, customer);
          if (queue_len_1 == queue_len_2)
          {
            if (ranf() < 0.50)
              schedule(2, 0.0, customer);
            else
              schedule(4, 0.0, customer);
          }
        }
        schedule(1, expntl(Ta), customer);
        break;

      case 2:  // ***** Request server #1
        if (request(server_1, customer, 0) == 0)
          schedule(3, Ts_1, customer);
        break;

      case 3:  // ***** Release server #1
        release(server_1, customer);
        count_1++;
        break;

      case 4:  // ***** Request server #2
        if (request(server_2, customer, 0) == 0)
          schedule(5, Ts_2, customer);
        break;

      case 5:  // ***** Release server #2
        release(server_2, customer);
        count_2++;
        break;
    }
  }

  // Compute (using Little's Law) mean system wait
  wait_1 = ((double) Lq(server_1) + U(server_1)) * (time() / count_1);
  wait_2 = ((double) Lq(server_2) + U(server_2)) * (time() / count_2);
  mean_wait = ((double) count_1 / (count_1 + count_2)) * wait_1 +
              ((double) count_2 / (count_1 + count_2)) * wait_2;

  // Output simulation results
  printf("============================================================== \n");
  printf("=       ***** Results from dual queue simulation *****       = \n");
  printf("============================================================== \n");
  if (balance_mode == 0)
    printf("=  >>> Using random server selection \n");
  if (balance_mode == 1)
    printf("=  >>> Using round robin server selection \n");
  if (balance_mode == 2)
    printf("=  >>> Using shortest queue server selection \n");
  printf("= \n");
  printf("=  Total simulation time         = %4.3f sec \n", time());
  printf("=  Mean interarrival time        = %4.3f sec \n", Ta);
  printf("=  Facility #1 mean service time = %4.3f sec \n", Ts_1);
  printf("=  Facility #2 mean service time = %4.3f sec \n", Ts_2);
  printf("= \n");
  printf("=  Facility #1 utilization       = %4.3f %%  \n", 100 * U(server_1));
  printf("=  Facility #1 customer count    = %ld       \n", count_1);
  printf("=  Facility #1 mean system wait  = %4.3f sec \n", wait_1);
  printf("= \n");
  printf("=  Facility #2 utilization       = %4.3f %%  \n", 100 * U(server_2));
  printf("=  Facility #2 customer count    = %ld       \n", count_2);
  printf("=  Facility #2 mean system wait  = %4.3f sec \n", wait_2);
  printf("= \n");
  printf("=  Mean wait for a customer      = %4.3f sec \n", mean_wait);
  printf("= \n");
  printf("============================================================== \n");
}