[attachment=14558]
SIMULATION IN QUEUE
What is simulation?
The word simulate means to imitate or to have the same effect as.
Simulation is the process of forming an abstract model from a real situation in order to understand the impact of modifications and the effect of introducing various strategies on the situation.
It allows the user to experiment with real & proposed situation otherwise impossible or impractical
The major advantage of simulation is that it permits experiments without modifying the real situation.
The best example for it is Military Operations, they are safer to simulate rather than field test.
Large numbers of alternative modifications to a situation may be included in a simulation, and their results can be studied systematically in a comparative fashion.
Along with the advantage, there are disadvantages also. In the hospital, some machines are there which cant be simulated, if they are it causes to danger, it affect the patient’s life.
A system is a group of objects interacting in order to produce some result.
For example, A factory is a group of people and machines working together to produce some products.
System can be either Continuous System or Discrete System
Continues System has parameters which can take any real value in some given intervals, such as Temperature or Pressure Measurements
Discrete System have parameters which can only take values from a fixed number of choices, such as produce in a grocery store
To simulate a queueing system, must follow the four things :
The number of events & how they affect the system
The number of Servers
The distribution of arrival times
The expected service time.
K
Two type of Simulation is there :
Time-Driven Simulation : A main clock is used to keep track of simulation time. The clock is allowed to increase one unit at a time. After each increase the program must examine each event to determine if it is to occur at this time.
Event-Driven Simulation : The program in this case must examine all events in the model to determine which is to happen next. i.e. it is based on the events.
Queue Simulation Example
Let us simulate a saltwater taffy store on a beach board-walk.
The store has one window, and a clerk can service only one customer at a time. The store also ships boxes of taffy anywhere in the country. The time to serve customers varies between 1 and 10 minutes.
We will study the store’s activity over a hypothetical day. The store is open 8 hours per day, 7 days a week. To simulate a day, we build a model that runs for 480 minutes (8x60=480).
We assume that events start and stop in 1-minute interval.
We assume that, on average, a customer arrives every 4 minutes. We simulate the arrival rate using a random-number generator that returns a value between 1 and 4. It the number is 4, a customer has arrived.
We start processing a customer when the server is idle.
In each minute of the simulation, the simulator needs to determine whether the clerk is busy or idle. If it is idle, the next customer in the queue can be served. If it is busy, the waiting customers remain in the queue.
At the end of each minute, the simulation determines whether it has completed the processing for the current customer.
The processing time for the current customer is simulated by a random-numbers generator when the customer processing is started. Then, for each customer, we loop the required number of minutes to complete the transaction.
When the customer has been completely served, we gather statistics about the sale and set the server to an idle state.