Advanced Modelling Features
Overview
In a process-oriented model, queues are used to synchronise simulation processes which are conceptually acting concurrently. For example, in our simple model of the loading zone of a container terminal, arriving trucks had to wait until a van carrier was available for service. DESMO-J's core.advancedModellingFeatures package provides higher-level constructs to aid the model designer in expressing synchronisation in more problem relevant terms.
These constructs can only be used with simulation processes. Processes are automatically inserted into internal queues and automatically activated again when they leave the queue. Relevant statistical measures are automatically recorded and reported.
DESMO-J supports four different patterns of synchronisation:
- Capacity constrained resources (class Res). Processes wait until sufficient resource capacity is available to proceed.
- Producer/consumer relationships with unlimited capacity buffers (class Bin).
- Conditional waiting (class CondQueue) until a specified model state has occurred.
- direct process co-operation (class WaitQueue) in the form of asymmetric master-slave relationships.
In addition to these process synchronisation constructs, DESMO-J provides a simple form of direct process communication via the interrupt() method of the SimProcess class. This method allows to interrupt the execution of an active process.
Note: The examples in this section assume that you are familiar with how to build a process-oriented model in DESMO-J. If you need an in-depth introduction to process-oriented modelling with DESMO-J, please turn to the Processes Step by Step section first.