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Optimization Tools and Techniques

Use the Model Advisor to Optimize a Model for Code Generation

You can use the Model Advisor to analyze a model for code generation and identify aspects of your model that impede production deployment or limit code efficiency. You can select from a set of checks to run on a model's current configuration. The Model Advisor analyzes the model and generates check results providing suggestions for improvements in each area. Most Model Advisor diagnostics do not require the model to be in a compiled state; those that do are noted.

Before running the Model Advisor, select the target you plan to use for code generation. The Model Advisor works most effectively with ERT and ERT-based system target files.

Use the following examples to investigate optimizing models for code generation using the Model Advisor:

Note

Example models rtwdemo_advisor2 and rtwdemo_advisor3 require Stateflow® and Fixed-Point Designer™ software.

For more information on using the Model Advisor, see Run Model Advisor Checks. For more information about the checks, see Simulink Coder Checks.

Design Tips for Optimizing Generated Code for Stateflow Objects

Do Not Access Machine-Parented Data In a Graphical Function

This restriction prevents long parameter lists from appearing in the code generated for a graphical function. You can access local data that resides in the same chart as the graphical function. For more information, see Reuse Logic Patterns by Defining Graphical Functions (Stateflow).

Be Explicit About the Inline Option of a Graphical Function

When you use a graphical function in a Stateflow chart, select Inline or Function for the property Function Inline Option. Otherwise, the code generated for a graphical function may not appear as you want. For more information, see Specify Properties of Graphical Functions (Stateflow).

Avoid Using Multiple Edge-Triggered Events in Stateflow Charts

If you use more than one trigger, you generate multiple code statements to handle rising or falling edge detections. If multiple triggers are required, use function-call events instead. For more information, see Activate a Stateflow Chart by Sending Input Events (Stateflow).

Combine Input Signals of a Chart Into a Single Bus Object

When you use a bus object, you reduce the number of parameters in the parameter list of a generated function. This guideline also applies to output signals of a chart. For more information, see Define Stateflow Structures (Stateflow).

Use Charts with Discrete Sample Times

The code generated for discrete charts that are not inside a triggered or enabled subsystem uses integer counters to track time instead of Simulink® provided time. This allows for more efficient code generation in terms of overhead and memory, as well as enabling this code for use in software-in-the-loop (SIL) and processor-in-the-loop (PIL) simulations.

Additional Optimization Techniques

You can apply the following techniques to optimize a model for code generation:

  • For Embedded Coder® users, if your application uses only integer arithmetic, clear the Support floating-point numbers parameter in the Software environment section of the Interface pane so that the generated code does not contain floating-point data or operations. When this parameter is cleared, an error is raised if noninteger data or expressions are encountered during code generation. The error message reports the offending blocks and parameters.

  • Disable the Configuration Parameters > Code Generation > Interface > Advanced parameters > MAT-file logging parameter. Deselecting this parameter eliminates extra code and memory usage for initializing, updating, and cleaning-up logging variables. In addition, the code generated to support MAT-file logging invokes malloc, which can be undesirable for your application.

  • Use the Upgrade Advisor to upgrade older models (saved by prior versions or the current version) to use current features. For details, see Model Upgrades.

  • Before building, set optimization flags for the compiler (for example, -O2 for gcc, -Ot for the Microsoft® Visual C++® compiler).

  • Directly inline C/C++ S-functions into the generated code by writing a TLC file for the S-function. For more information, see Accelerate Simulation, Reuse Code, or Protect Intellectual Property by Using S-Function Target and see Inline C MEX S-Functions.

  • Use a Simulink data type other than double when possible. The available data types are Boolean, signed and unsigned 8-, 16-, and 32-bit integers, and 32- and 64-bit floats (a double is a 64-bit float). For more information, see About Data Types in Simulink. For a block-by-block summary, click showblockdatatypetable or type the command in the Command Window.

  • For tunable block parameters that you configure to store in memory in the generated code, you can match parameter data types with signal data types to eliminate unnecessary typecasts and C shifts. Where possible, store parameter values in small integer data types. See Parameter Data Types in the Generated Code.

  • Remove repeated values in lookup table data.

  • Use the Merge block to merge the output of signals wherever possible. This block is particularly helpful when you need to control the execution of function-call subsystems with a Stateflow chart. The following model shows an example of how to use the Merge block.

    When more than one signal connected to a Merge block has a non-Auto storage class, all non-Auto signals connected to that block must be identically labeled and have the same storage class. When Merge blocks connect directly to one another, these rules apply to the signals connected to any of the Merge blocks in the group.

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