4. GPSS/H Queueing Models
is often wrongly classified as a simulator for queueing systems. That's a mistake: recent GPSS-implementations,
especially GPSS/H, are universal simulation systems, suitable for simulating any model
in discrete, event-oriented simulation.
What is true is that GPSS had originally been designed as a simulator for queueing systems and even
today it is still very suitable for this purpose.
That might be the reason for beginning the introduction to GPSS with examples of queueing models.
In the following chapter 4 we will, with the help of these examples, discuss the original,
easy to describe classes of entities and language elements. In chapter 5
we will have to proof that GPSS/H is a truly universal simulation language, whose usage today
extends the original one by far.
Transactions (short Xacts)
are components needed for the simplest queueing system, the single server
or single channel queueing system.
Here, Transactions are used for mapping demands or requests and a Facility for mapping the service station.
This introductory example will finally be supplied with statements necessary for its animation.
GPSS/H language elements can be divided into these three classes.
The paragraph describes the basic features of these language components and their interaction.
The transition from a single server to multi-channel queueing systems
will be combined with an introduction to
the following classes of model elements: Queue
A queueing system contains several service stations, requested by demands.
For its reconstruction it is necessary to be able to split and gather streams of requests or demands,
the so-called Transactions in GPSS. By using Logic Switches and the Blocks
the programmer can meet these requirements.
In contrast to the classic theory of queueing systems, there are hardly any applications using homogeneous request streams,
which consist of equal elements. Transactions can be assigned with attributes or Parameters
carrying different values and thus allow modeling their different behavior. Additional attributes are their Priority
and their Mark Time word
||Fri 05-27-11 06:54 GMT
|English Translation:||A. Kreutzberg|
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