//================================================= file = loadBalance2.c =====
//=  A CSIM simulation of a stateless load balancer for two queues            =
//=   - Uses facility sets                                                    =
//=============================================================================
//=  Notes: 1) Values for lambda and mu are set in the main program           =
//=         2) Type of load balancing is set in #define                       =
//=         3) Ignore warning on build                                        =
//=---------------------------------------------------------------------------=
//= Example execution:                                                        =
//=                                                                           =
//=  *** BEGIN SIMULATION ***                                                 =
//=  =============================================================            =
//=  ==     *** CSIM Stateless Load Balancing simulation ***    ==            =
//=  =============================================================            =
//=  = >>> Random load balancing                                              =
//=  = Lambda   = 1.600000 cust/sec                                           =
//=  = Mu       = 1.000000 cust/sec                                           =
//=  =============================================================            =
//=  = Total CPU time     = 2.387000 sec                                      =
//=  = Total sim time     = 1000000.000000 sec                                =
//=  = Total completions  = 1598977 cust                                      =
//=  =------------------------------------------------------------            =
//=  = >>> Simulation results                                    -            =
//=  =------------------------------------------------------------            =
//=  = Utilization        = 80.030815 %                                       =
//=  = Mean num in system = 4.044433 cust                                     =
//=  = Mean response time = 5.062039 sec                                      =
//=  = Mean service time  = 1.001671 sec                                      =
//=  = Mean throughput    = 0.798973 cust/sec                                 =
//=  =------------------------------------------------------------            =
//=  = Utilization        = 80.173774 %                                       =
//=  = Mean num in system = 4.105401 cust                                     =
//=  = Mean response time = 5.131725 sec                                      =
//=  = Mean service time  = 1.002167 sec                                      =
//=  = Mean throughput    = 0.800004 cust/sec                                 =
//=  =============================================================            =
//=  *** END SIMULATION ***                                                   =
//=---------------------------------------------------------------------------=
//=  Build: standard CSIM build                                               =
//=---------------------------------------------------------------------------=
//=  Execute: loadBalance2                                                    =
//=---------------------------------------------------------------------------=
//=  Author: Ken Christensen                                                  =
//=          University of South Florida                                      =
//=          WWW: http://www.csee.usf.edu/~christen                           =
//=          Email: christen@csee.usf.edu                                     =
//=---------------------------------------------------------------------------=
//=  History: KJC (06/25/13) - Genesis (from mm1_csim.c)                      =
//=============================================================================
//----- Includes --------------------------------------------------------------
#include <stdio.h>      // Needed for printf()
#include "csim.h"       // Needed for CSIM stuff

//----- Defines ---------------------------------------------------------------
#define SIM_TIME 1.0e6  // Total simulation time in seconds
#define TYPE         1  // Balance type (1 = random, 2 = round robin)

//----- Globals ---------------------------------------------------------------
FACILITY Server[2];      // Declaration of CSIM Server facility set

//----- Prototypes ------------------------------------------------------------
void generate(double lambda, double mu);       // Customer generator
void balancer(double mu);                      // Load balancer
void queuex(int index, 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)

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

  // CSIM initializations
  facility_set(Server, "Server #1 and #2", 2);

  // Parameter initializations
  lambda = 1.6;
  mu = 1.0;

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

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

  // Output results
  printf("============================================================= \n");
  printf("==     *** CSIM Stateless Load Balancing simulation ***    == \n");
  printf("============================================================= \n");
  if (TYPE == 1)
    printf("= >>> Random load balancing \n");
  else if (TYPE == 2)
    printf("= >>> Round Robin load balancing \n");
  printf("= Lambda   = %f cust/sec   \n", lambda);
  printf("= Mu       = %f cust/sec   \n", mu);
  printf("============================================================= \n");
  printf("= Total CPU time     = %f sec      \n", cputime());
  printf("= Total sim time     = %f sec      \n", clock);
  printf("= Total completions  = %d cust     \n",
    completions(Server[0]) + completions(Server[1]));
  printf("=------------------------------------------------------------ \n");
  printf("= >>> Simulation results                                    - \n");
  printf("=------------------------------------------------------------ \n");
  printf("= Utilization        = %f %%       \n", 100.0 * util(Server[0]));
  printf("= Mean num in system = %f cust     \n", qlen(Server[0]));
  printf("= Mean response time = %f sec      \n", resp(Server[0]));
  printf("= Mean service time  = %f sec      \n", serv(Server[0]));
  printf("= Mean throughput    = %f cust/sec \n", tput(Server[0]));
  printf("=------------------------------------------------------------ \n");
  printf("= Utilization        = %f %%       \n", 100.0 * util(Server[1]));
  printf("= Mean num in system = %f cust     \n", qlen(Server[1]));
  printf("= Mean response time = %f sec      \n", resp(Server[1]));
  printf("= Mean service time  = %f sec      \n", serv(Server[1]));
  printf("= Mean throughput    = %f cust/sec \n", tput(Server[1]));
  printf("============================================================= \n");

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

//=============================================================================
//==  Process 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);
    balancer(service_time);
  }
}

//=============================================================================
//==  Process to load balance                                                ==
//=============================================================================
void balancer(double mu)
{
  static int index = 0;          // Queue index

  create("balancer");

  // Random (Type 1) or Round Robin (Type 2)
  if (TYPE == 1)
    index = random(0, 1);
  else if (TYPE == 2)
    index = (index + 1) % 2;

  // Send to appropriate queue
  if (index == 0)
    queuex(index, mu);
  else if (index == 1)
    queuex(index, mu);
}

//=============================================================================
//==  Process for single server queue                                        ==
//=============================================================================
void queuex(int index, double service_time)
{
  create("queuex");

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