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bank11: A simple example using a Monitor
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:Author: G A Vignaux  
:Date: $Date: 2004/02/19 $

Description
-------------

The purpose of this example is show *Monitor* in use to estimate the
average waiting time for customers in a bank. 

The example is taken from the *Bank* tutorial, included in the SimPy
documentation. It simulates a bank with customers who arrive at random
to be served at one of two counters. A customer chooses the shortest
queue to join and takes a random time to be served.


Code
-----

.. include:: bank11.py
   :literal:


Comments
---------

The *Customer* class is a SimPy process with a PEM called *visit*. On
arrival the time is recorded and the shortest queue chosen (variable
*join*). The function *NoInSystem* is used to find the number at each
counter. A request is made for that particular *counter[join]*, and,
when service starts, the waiting time, *wait* is calculated. This is
Monitored. The actual time for service, *tib* is sampled (from a
distribution with mean *timeInBank*) and the counter held for that
time before release.

Customers are generated using the *Source* process which creates and
activates a *Customer* at exponential (random) delays with mean
*interval*.

The problem is set up in the function *model*. Doing this within a
function is a little clumsy as it involves the use either of a number
of arguments or, as I have done here, of global variables, like
*counter* and *waitMonitor*, but it means that a number of independent
runs can be made within the same script.

Here I did not use the full power of this technique. I ran a single
run of 50 customers (in the call of *generate*) for a maximum
time of 2000. The result is:

 
.. include:: bank11.out
   :literal: