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77 lines
3.1 KiB
Markdown
| [Home](/trick) → [Tutorial Home](Tutorial) → Trick Simulation Architecture |
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<!-- Section -->
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<a id=architecture-of-a-trick-simulation></a>
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## Architecture of a Trick Simulation
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**Contents**
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* [The Simulation Definition File](#the-simulation-definition-file)<br>
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* [The Parts of an S_define](#the-parts-of-an-sdefine)<br>
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***
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We divided our non-Trick simulation code into:
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* Variable declarations
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* Variable default data assignments
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* Variable initialization by calculation
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* Running the sim
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* Cleanup/Shutdown
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A Trick-based simulation is organized similarly and is defined in a simulation definition file (S\_define). The S\_define specifies the data types, functions/methods and scheduling requirements for the simulation's models. Trick generates a simulation executable based on the S\_define.
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---
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<a id=the-simulation-definition-file></a>
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### The Simulation Definition File (S_define)
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### Example S_define File
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The S_define file specifies and ties together everything necessary to build a
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simulation:
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* The source code that implements the simulation models.
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* The data-types for the model(s) and Trick utilities.
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* The specific variable instances of the data-types.
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* Job scheduling Specifications
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---
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<a id=the-parts-of-an-sdefine></a>
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### The Parts of an S_define
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At the top of the S_define file is a special comment block. The comment block contains Trick keywords followed by information in parentheses.
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The ```PURPOSE:``` keyword (note that the colon is part of the keyword)
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specifies a brief description of the S\_define file. It is mandatory.
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```LIBRARY DEPENDENCIES``` specifies the model source files that need to be
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compiled before building the simulation. Trick headers in these files
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may specify additional source code dependencies, and so forth. Libraries may
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also be specified for linking into the final simulation executable.
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The ```default_trick_sys.sm``` file defines variables and data-types necessary
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to provide the standard features of any Trick-based simulation. Its inclusion
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is mandatory. Every S\_define file should contain the following line:
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```#include "sim_objects/default_trick_sys.sm"```
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Header files that supply data-types for user-defined models should be
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included using ```##include```. Note the double hash (#).
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```Trick::SimObject``` is the base-class used to 1) declare data members of a model, and 2) set job scheduling specifications for a model. The example above declares a new class ```CannonSimObject``` that contains one data member ```cannon```, and three job specifications.
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Once a new SimObject-derived class has been defined, we can create an instance of it.
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In the example above the variable ```dyn``` is an instance of ```CannonSimObject```.
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That is, it is one instance of our cannonball model. If we were to create a second instance of
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```CannonSimObject``` then our simulation would contain two independently runnable cannonball models.
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In the following sections we'll create the parts for a Trick-based cannonball simulation, and build it.
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---
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[Next Page](ATutAnalyticSim)
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