AG VLSI Design and Architecture

SFB 501 - Project D1: Application System "Buildings"

PSiGene Pattern Code Generator

Description

All patterns provided by the catalog are realized within PSiGene as VisualWorks classes. This implementation ignores the informal parts of the pattern description (e.g. Intent) and emphasizes the Participants as well as the Implementation part. The implemented patterns are descendants of a common superclass AbstractPattern. This class provides the protocol needed to bind patterns, to generate code, and to create error reports for the user.

The following figure (figure 1) shows a small example of how code generation usually is done in PSiGene. Input to PSiGene is a simple class model consisting of a class Room that aggregates several Radiators. Each Radiator has a method q to calculate the heatflow affecting its surroundings (here: the room in which the radiator is located). To this class model the pattern FollowRelationAndSum is bound. The purpose of this binding is to follow the radiators relation in order to collect and sum up the heat flows from all radiators in a certain room.
Part of the pattern FollowRelationAndSum is shown on the upper right corner of figure 1. The pattern has two code templates to generate a method that traverses a relation and sums up values from adjoining objects. One of these two templates is used during the code generation depending on the cardinality of the relation that should be traversed (If the relation radiators would have been of cardinality 1:1 different code than shown in the example would have generated .).

Figure 1

The generation of simulation code is divided into two phases, which are performed automatically, without manual intervention:

• In the binding phase, an instance of a pattern class is created for every pattern bound to the simulator's class model. In this phase, no code is generated. The set of all instances is then checked for completeness, based on the formal parameters defined by each pattern. A report is generated for the user of PSiGene. This report includes information about missing and wrong bindings for every single pattern instance so that errors in the binding description can easily be identified and corrected. In addition to the checks performed by our pattern editor, these tests include correct library usage and availability of manually written code (if needed).
• In the generation phase, all pattern instances are asked to generate code for the objects they are bound to. There is no `master generator': each pattern instance is responsible for its own code portion (by providing a code generation method), making the generation process flexible and easily extendible by simply implementing new pattern classes.

The implemented patterns are structured as shown in figure 2:

Figure 2