_AN ARCHITECTURE FOR NETWORK SIMULATION_
by Peter D. Varhol

Listing One

procedure create(var param, inV,outV:VisSimArg);
export;
var i: integer;

begin
if param[0] <> 0 then
        q_number := trunc(param[0])
        else
        begin
                q_number := 1;
                param[0] := q_number
        end;
c[q_number] := false;

if {(inV[0] > 0) and} q_remaining[q_number] <= 0 then
begin
        new(next[q_number]);
        created[q_number] := true;
        q_remaining[q_number] := InV[0];
        packet_created[q_number] := cust_created[q_number] + 1;
        packet_id[q_number] := customer_id[q_number] + 1;
        next[q_number]^.customer_number := customer_id[q_number];
        next[q_number]^.destination := q_number;
        next[q_number]^.priority := inV[1];
        next[q_number]^.wait_time := 0;
        next[q_number]^.serve_time := 0;
        next[q_number]^.preempt_time := 0;
        next[q_number]^.link := nil;
        next[q_number]^.use[1] := InV[2];
        if inV[3] <> 0 then 
                if first[q_number,1] = 0 then
                        next[q_number]^.use[1] := InV[2]
                        else
                        for i := 1 to max_data do
                                next[q_number]^.use[i] := first[q_number,i];
end;
if created[q_number] = false then
        outV[0] := 0
        else
                outV[0] := q_number;
end;


Listing Two

procedure createSS(var param : VisSimArg; var runCount : shortint);
export;
var i : integer;
begin
for q_number := 1 to maxqueues do
        begin
                created[q_number] := false;
                packet_id[q_number] := 0;
                q_remaining[q_number] := 0;
                arrive_sum[q_number] := 0;
                packet_created[q_number] := 0;
                q_time[q_number] := 0;
                for i := 1 to max_data do
                        first[q_number,i] := 0;
        end
end;

function createPA(var ppCount : shortint) : longint;
export;
var paramalloc : byteptr;
begin
        ppCount := 1;
        createPA := GetMem(paramalloc,16);
end;

function createPC(var param : VisSimArg) : PChar;
export;
begin
        createPC := 'Queue #'
end;


Listing Three

#include "windows.h"
#include "vsuser.h"

int DLLInst;

  USER_MENU_ITEM trans[] = {
  {"Discrete Event", "tran2", -1,-1,0, "Discrete event simulation building blocks"},
  {"createTransaction", "create", 3,1,48, "Creates new transactions"},
  {"queue", "queue_block", 1,1,184, "First-in, first-out queue"},
  {"transactionManager", "t_manager", 1,1,32, "Manages transaction flow between queues and servers"},
  {"server", "server", 2,1,32, "Services a transaction"},
  {"departSystem", "depart", 1,0,16, "Removes a transaction at the end of a system"},
  {0}
  };

  USER_MENU_ITEM stats[] = {
  {"Discrete Statistics", "tran2", -1,-1,0, "Collects statistical data on simulation"},
  {"utilizationRate", "utilization", 1,1,16, "Cumulatively computes utilization rate"},
  {"queueLength", "queue_length", 1,1,16, "Computes the length of the queue"},
  {"waitingTime", "waiting_time", 1,1,16, "Cumulatively computes time waiting in queue"},
  {"timeInSystem", "system_time", 1,1,16, "Cumulatively computes waiting and service times combined"},
  {"transactionsGenerated", "transactions_generated", 1,1,16, "Computes number of transactions produced in a simulation run"},
  {"transactionsServed", "transactions_served", 1,1,16, "Computes number of transactions served in a simulation run"},
  {"transactionsLost", "transactions_lost", 1,1,16, "Cumulatively computes proportion of transactions lost in a finite queue"},
  {"transactionTime", "trans_time", 1,1,16, "Foobar"},
  {0}
  };

  USER_MENU_ITEM utils[] = {
  {"Discrete Utilities", "tran2", -1,-1,0, "Utilities from manipulating a simulation"},
  {"poissonRandomNumbers", "poisson", 1,1,16, "Produces a stream of Poisson-distributed random numbers"},
  {"exponentialRandomNumbers", "exponential", 1,1,16, "Produces a stream of exponentially-distributed random numbers"},   {"generatePriorities", "generate_priority", 1,1,16, "Randomly generates priority levels for the priority queue"},
  {"readTransactionID", "read_transaction", 1,1,16, "Reads the unique ID number of a transaction"},
  {"insertData", "insert_data", 1,1,160, "Writes user-defined data into a transaction"},
  {"retrieveData", "retrieve_data", 1,1,160, "Reads user-defined data from a transaction"},
  {"fork", "fork", 1,2,8, "Causes a branching of a random number stream"},
  {"delayTransaction", "delay", 2,1,16, "Delays a transaction passing from a server to a serial queue"},
  {"simulationTime", "sim_time", 1,1,16, "Computes the internal simulation running time"},
  {0}
  };


void EXPORT PASCAL vsmInit()
{
  setUserBlockMenu(trans);
  setUserBlockMenu(stats);
  setUserBlockMenu(utils);
}  


Example 1: Packet structure

packetptr = ^packet;
packet = record
        packet_number : double;
        priority : double;
        wait_time : double;
        serve_time : double;
        preempt_time : double;
        destination : double;
        t_mgr : double;
        servers : double;
        use : user;
        link : packetptr
end;