s2rout4.m

Industrial Mathematics

% Routine 2.4 
a = 1;                   % arrival time parameter
m = 10;                  % number of processors
mu = 8;                  % mean processing time
sig = 3;                 % s.d. of the processing time
Q = 1:m;                 % set the # processors = m
Q = 0*Q;                 % initialize the queue of m processors
wait=0;                  % initialize total waiting time
N = 10000;               % experiment with N customers
                         % store opens
for k=1:N                % watch N customers
 T = -a*log(1-rand);     % arrival time of new customer C
 S = mu + sig*randn;     % compute time to service C
 Q = max(Q - T, 0);      % update the queues to present
 t = min(Q);             % shortest line wait time t
 for i=1:m               % check to see which line is shortest:
   if Q(i) <= t       
     j = i;                
     break;
     end;                % endif
  end;                   % queue j has shortest wait
  wait = wait + Q(j);    % add in time until C to reaches cashier
  Q(j) = Q(j) + S;       % time for C to clear queue j
end;                     % store closes
wait/N                   % average time to reach cashier