Page 126 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes A Single-sever service node consists of a server plus its queue.

Queue discipline: The algorithm used when a job is selected from the queue to enter service
FIFO – first in, first out
LIFO – last in, first out

SIRO – serve in random order
Priority – typically shortest job first (SJF)
FIFO is also known as first come, first serve (FCFS)
1. The order of arrival and departure are the same
2. This observation can be used to simplify the simulation

Service is non-preemptive
Once initiated, service of a job will continue until completion
Service is conservative

Server will never remain idle if there is one or more jobs in the service node

!
Caution Unless otherwise specified, assume FIFO with infinite queue capacity.

Specification Model

For a job i:
1. The arrival time is a
i
2. The delay in the queue is d
i
3. The time that service begins is b = a + d
i i i
4. The service time is s
i
5. The wait in the node is w = d + s
i i i
6. The departure time is c = a + w
i i i

Arrivals

1. The interarrival time between jobs i “– 1 and i is
r = a – a
i i i–1
where, by definition, a = 0
0

120 LOVELY PROFESSIONAL UNIVERSITY