M/M/1排队系统性能仿真代码（MATLAB） - 数学建模社区-数学中国

可能有点儿乱啊~~嘿嘿

%mm1 simulation in matlab
clc;clear;

ST_Idle=0;
ST_Busy=1;

EV_NULL=0;
EV_Arrive=1;
EV_Depart=2;
EV_LEN=3;

Q_LIMIT=1000;

% next_event_type=[];
% num_custs_delayed=[];
% num_delays_required=[];
% num_events=[];
% num_in_q=[];
% server_status=[];
% area_num_in_q=[];
% area_server_status=[];
% mean_interarrival=[];
% mean_service=[];
% sim_time=[];
% time_last_event=[];
% total_of_delays=[];
%
time_arrival=[]; %到达时刻

time_next_event=zeros(1,EV_LEN);
%仿真参数
num_events=EV_LEN-1;
mean_interarrival=1;
mean_service=.5;
num_delays_required=2000; %

outfile=fopen('mm1.txt','w');
fprintf(outfile, 'Single-server queueing system\n\n');
fprintf(outfile, 'Mean interarrival time%11.3f minutes\n\n',mean_interarrival);
fprintf(outfile, 'Mean service time%16.3f minutes\n\n', mean_service);
fprintf(outfile, 'Number of customers%14d\n\n', num_delays_required);

%%%%%%%%%%%%%part1
sim_time=0.0;
% /* Initialize the state variables. */

server_status = 0;%idle
num_in_q = 0;
time_last_event = 0.0;

% /* Initialize the statistical counters. */

num_custs_delayed  = 0;
total_of_delays = 0.0;
area_num_in_q    = 0.0;
area_server_status = 0.0;

%    /* Initialize event list.  Since no customers are present, the departure
%       (service completion) event is eliminated from consideration. */
time_next_event(EV_Arrive) = sim_time + randexp(mean_interarrival);
time_next_event(EV_Depart) = 1.0e+230;

%%%%%%%%%%%%part2
while (num_custs_delayed < num_delays_required)
%Run the simulation while more delays are still needed.
%/* Determine the next event. */

   min_time_next_event = 1.0e+290;
   next_event_type = 0;

%/* Determine the event type of the next event to occur. */

for i = 1: num_events
      if (time_next_event(i) < min_time_next_event)
         min_time_next_event = time_next_event(i);
         next_event_type    = i;
      end
end

%/* Check to see whether the event list is empty. */

if (next_event_type == 0)

%/* The event list is empty, so stop the simulation. */

fprintf(outfile, '\nEvent list empty at time %f', sim_time);
exit(1);
end
%/* The event list is not empty, so advance the simulation clock. */

sim_time = min_time_next_event;

%/* Update time-average statistical accumulators. */

double time_since_last_event;

%/* Compute time since last event, and update last-event-time marker. */

time_since_last_event = sim_time - time_last_event;
time_last_event = sim_time;

%/* Update area under number-in-queue function. */

area_num_in_q=area_num_in_q + num_in_q * time_since_last_event;

%/* Update area under server-busy indicator function. */

area_server_status =area_server_status + server_status * time_since_last_event;

%/* Invoke the appropriate event function. */

%%%%%%%%%%%%%arrival

if(next_event_type==EV_Arrive)
double delay;

%/* Schedule next arrival. */

time_next_event(1) = sim_time + randexp(mean_interarrival);

%/* Check to see whether server is busy. */

if (server_status == ST_Busy)

%/* Server is busy, so increment number of customers in queue. */

num_in_q=1+num_in_q;

%/* Check to see whether an overflow condition exists. */

if (num_in_q > Q_LIMIT)
%/* The queue has overflowed, so stop the simulation. */

            fprintf(outfile, '\nOverflow of the array time_arrival at');
            fprintf(outfile, ' time %f', sim_time);
            exit(2);
         end
%/* There is still room in the queue, so store the time of arrival of the arriving customer at the (new) end of time_arrival. */

time_arrival(length(time_arrival)+1)=sim_time;

else
%/* Server is idle, so arriving customer has a delay of zero. (The following two statements are for program clarity
%and do not affect the results of the simulation.) */

         delay = 0.0;
         total_of_delays =total_of_delays + delay;

%/* Increment the number of customers delayed, and make server busy. */

         num_custs_delayed = 1 + num_custs_delayed;
         server_status = ST_Busy;

%/* Schedule a departure (service completion). */

         time_next_event(EV_Depart) = sim_time + randexp(mean_service);
      end % if (server_status == ST_Busy)
%%%%%%%%depart
else
         double delay;

%/* Check to see whether the queue is empty. */

if (num_in_q == 0)

% /* The queue is empty so make the server idle and eliminate the departure (service completion) event from consideration. */

         server_status    = ST_Idle;
         time_next_event(EV_Depart) = 1.0e+230;

      else

%/* The queue is nonempty, so decrement the number of customers in queue. */

num_in_q=num_in_q-1;

%/* Compute the delay of the customer who is beginning service and update the total delay accumulator. */

delay = sim_time - time_arrival(1);
total_of_delays =total_of_delays + delay;

%/* Increment the number of customers delayed, and schedule departure. */

num_custs_delayed = 1 + num_custs_delayed;
time_next_event(EV_Depart) = sim_time + randexp(mean_service);

%/* Move each customer in queue (if any) up one place. */

         tempForPop=time_arrival(2:length(time_arrival));
         time_arrival=tempForPop;
      end %if (num_in_q == 0)

end %if(next_event_type==EV_Arrive)

end %while

%%%%%%%%%% part 3
%/* Invoke the report generator and end the simulation. */

fprintf(outfile, '\n\nAverage delay in queue%11.3f minutes\n\n',total_of_delays / num_custs_delayed);
fprintf(outfile, 'Average number in queue%10.3f\n\n',area_num_in_q / sim_time);
fprintf(outfile, 'Server utilization%15.3f\n\n',area_server_status / sim_time);
fprintf(outfile, 'Time simulation ended%12.3f minutes', sim_time);
fclose(outfile);