Chapter3 general principles of discrete event simulation
General Principles of Discrete Event Simulation Chapter 3
Terminologies System Model System State Entity Attributes List Event Event Notice Event List Activity Delay Clock
What is Discrete Event Simulation? DES is used for systems where the state of a system changes in discrete points in time. A system can change in only countable number of points in time. Makes use of a Time-Advance Algorithm.
Time-Advance Algorithm (Event Scheduling) This method requires an event list. The Simulation Clock Time will progress only up to the time when the event is expected to occur.
Time-Advance Algorithm (Event Scheduling) Time Line Service Begins Arrival Event Delay Activity Departure Event Entity (Customer) i X X X Customer Behavior inside Single-Server Queue
World Views It is the orientation or perspective that the modeler will adapt when modeling. Event Scheduling Process-Interaction Activity Scanning
Event Scheduling An analyst concentrates on events and their effect on system state.
Process-Interaction The analyst thinks in terms of the processes. The analyst defines the model in terms of entities or objects and their life cycle as they flow through the system. The process is the life cycle of the entity inside the system. The life cycle consist of various events and activities. These processes will force the entity to interact (such as queue and wait) Follows the intuitive approach and most popular. Allows for a high level description of the process flow. A process is a time-sequence list of events, activities, and delays that define the cycle of one entity as it moves through the system.
Activity Scanning A modeler concentrates on the activities of a model and those conditions, simple or complex, that allow an activity to begin. Can lead to slow run times due to repeated scanning of the activity list and check whether an activity can begin.