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Remove Code for Blocks That Have No Effect on Computational Results

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This example shows how the code generator optimizes generated code by removing code that has no effect on computational results. This optimization:

  • Increases execution speed.

  • Reduces ROM consumption.

Example

In the modelrtwdemo_blockreduction, a Gain block of value1.0is in between Inport and Outport blocks.

model ='rtwdemo_blockreduction'; open_system(model);

Generate Code

Create a temporary folder for the build and inspection process.

currentDir=pwd; [~,cgDir]=rtwdemodir();

Build the model.

set_param(model,'BlockReduction','off'); slbuild(model)
### Starting build procedure for: rtwdemo_blockreduction ### Successful completion of build procedure for: rtwdemo_blockreduction Build Summary Top model targets built: Model Action Rebuild Reason ======================================================================================================== rtwdemo_blockreduction Code generated and compiled. Code generation information file does not exist. 1 of 1 models built (0 models already up to date) Build duration: 0h 0m 10.165s

This code is the code fromrtwdemo_blockreduction.c.

cfile = fullfile(cgDir,'rtwdemo_blockreduction_ert_rtw','rtwdemo_blockreduction.c'); rtwdemodbtype(cfile,'/* Model step function */',...'/* Model initialize function */', 1, 0);
/* Model step function */ void rtwdemo_blockreduction_step(void) { /* Outport: '/Out1' incorporates: * Gain: '/Gain' * Inport: '/In1' */ rtwdemo_blockreduction_Y.Out1 = 1.0 * rtwdemo_blockreduction_U.In1; }

Enable Optimization

  1. Open the Configuration Parameters dialog box.

  2. If theBlock reduction复选框没有被选中,选中它。

Alternatively, use the command-line API to enable the optimization.

set_param(model,'BlockReduction','on');

Generate Code with Optimization

slbuild(model)
### Starting build procedure for: rtwdemo_blockreduction ### Successful completion of build procedure for: rtwdemo_blockreduction Build Summary Top model targets built: Model Action Rebuild Reason ======================================================================================= rtwdemo_blockreduction Code generated and compiled. Generated code was out of date. 1 of 1 models built (0 models already up to date) Build duration: 0h 0m 8.8193s

Here is the optimized code fromrtwdemo_blockreduction.c.

cfile = fullfile(cgDir,'rtwdemo_blockreduction_ert_rtw','rtwdemo_blockreduction.c'); rtwdemodbtype(cfile,'/* Model step function */',...'/* Model initialize function */', 1, 0);
/* Model step function */ void rtwdemo_blockreduction_step(void) { /* Outport: '/Out1' incorporates: * Inport: '/In1' */ rtwdemo_blockreduction_Y.Out1 = rtwdemo_blockreduction_U.In1; }

Because multiplying the input signal by a value of1.0does not impact computational results, the code generator excludes the Gain block from the generated code. Close the model and clean up.

bdclose rtwdemoclean(模型);cd (currentDir)

Limitations

The code generator cannot remove blocks under these circumstances:

  • The block output is configured as a test point or has a storage class and the block input and output have different data types, complexities, or widths.

  • The block has a nonconstant sample time, has an output connected to a root outport, and has a source that has a constant sample time.

  • The block has multiple sources, some of which have constant sample times and some of which have nonconstant sample times.

  • The block output has a storage class and has a source that is muxed, is a virtual bus, is connected to a root outport, is configured as a test point, or has a storage class.

  • The block has an output that is connected to the block input.

  • The block is inside an Initialize Function subsystem, Reset Function subsystem, or Terminate Function subsystem whose output is connected to an outport of the subsystem.

  • The block has an output that is connected to a Subsystem Outport block that has an initial condition.

  • The block has an output that is connected to an outport of an Initialize Function subsystem, Reset Function subsystem, or Terminate Function subsystem.

  • The block has an output that is connected to an outport for which the parameterEnsure outport is virtualis selected.

  • The block has an output that is connected to an outport that has an initial condition parameter.

  • The block has an output that is connected to a Merge, a Vector Concatenate, or a Matrix Concatenate block.

  • The block has tunable run-time parameters.

  • The block is inside a reusable subsystem whose output is connected to a block outside the reusable subsystem.

  • The block has a continuous state.

  • The block has a discrete state and the states are logged or have a nonauto storage class.

  • The block is an S-Function, unless you usessSetBlockReductionto enable block reduction.

  • The block output is configured as a test point or has a storage class and its source is a block inside a different conditional subsystem.

See Also

Related Topics