Progressive Examples R.B. Lenin (rblenin@daiict.ac.in) Autumn 2007 - - PowerPoint PPT Presentation

Progressive Examples

R.B. Lenin (rblenin@daiict.ac.in) Autumn 2007

R.B. Lenin (rblenin@daiict.ac.in) () Progressive Examples Autumn 2007 1 / 48

Outline

1

Time Advance Mechanism

2

Concepts in Discrete Event Simulation

3

Basic Approaches for Constructing Discrete-Event Simulation Models

4

Prototypical Event-Scheduling Approach

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Examples Harbour problem Phone problem Camera shop problem Single-stage production system

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Time Advance Mechanism

Time Advance Mechanism

Synchronous simulation

Look at regular time points 0, ∆, 2∆, . . . ,. In continuous systems, it may be necessary to take very small ∆.

Asynchronous simulation

Jump from one event to the next and describe the changes in state at these moments.

We will concentrate on asynchronous simulation of discrete-event system.

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Concepts in Discrete Event Simulation

Concepts in Discrete Event Simulation

Entity: Any object or component in the system which requires explicit representation in the model

a server, a customer, a machine.

Attributes: The properties of a given entity.

the priority of a waiting customer, the routing of a job.

List: A collection of associated entities, ordered in some logical fashion.

all arriving customers are ordered in the queue by FCFS or by priority.

Event: An instantaneous occurrence that changes the state of a system.

an arrival of a new customer to a system.

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Concepts in Discrete Event Simulation

Concepts in Discrete Event Simulation · · ·

Event notice: A record of an event to occur at the current or some future time, along with any associated data necessary to execute the

• event. At a minimum, the record includes the event type and the

event time. Event list: A list of event notices to occur in the future, ordered by time of occurrence. It is also known as Future Event List (FEL). Activity: A duration of time of specified length which is usually known when it begins.

a service time or inter-arrival time.

Delay: A duration of time of unspecified indefinite length which is not known until it ends.

a customer’s delay in a LCFS waiting line depends on future arrivals.

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Concepts in Discrete Event Simulation

Concepts in Discrete Event Simulation · · ·

Sample paths: The state as a function of time is called the sample path. Clock: A variable representing simulation time.

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Basic Approaches for Constructing Discrete-Event Simulation Models

Basic Approaches for Constructing Discrete-Event Simulation Models

Event-scheduling approach.

Focuses on events, i.e., the moments in time when state changes occur.

Process-interaction approach.

Focuses on processes, i.e., the flow of each entity through the system.

In general-purpose languages, one mostly uses the event-scheduling approach.

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