fiaccel

Accelerate fixed-point code or convert floating-point MATLAB code to fixed-point MATLAB code

Syntax

fiaccel -options fcn

fiaccel -float2fixed float2fixed_cfg_name fcn

Description

fiaccel -options fcn translates the MATLAB^® file fcn.m to a MEX function, which accelerates fixed-point code. To use fiaccel, your code must meet one of these requirements:

• The top-level function has no inputs or outputs, and the code uses fi.

• The top-level function has an output or a non-constant input, and at least one output or input is a fi.

• The top-level function has at least one input or output containing a built-in integer class (int8, uint8, int16, uint16, int32, uint32, int64, or uint64), and the code uses fi.

fiaccel -float2fixed float2fixed_cfg_name fcn converts the floating-point MATLAB function, fcn to fixed-point MATLAB code.

Examples

Accelerate Fixed-Point MATLAB Code

This example shows how to accelerate fixed-point MATLAB code using the fiaccel function.

Define a function that computes the moving average.

type("moving_average.m")

function [avg,z] = moving_average(x,z)
%#codegen

if nargin < 2
    z = fi(zeros(10,1),1,16,15);
end


z(2:end) = z(1:end-1);  % Update buffer
z(1) = x;               % Add new value
avg = mean(z);          % Compute moving average
end

Create a test file.

type("test_moving_average.m")

function avg = test_moving_average(x)
%#codegen

if nargin < 1
    x = fi(rand(100,1),1,16,15);
end

z = fi(zeros(10,1),1,16,15);
avg = x;
for k = 1:length(x)
    [avg(k),z] = moving_average(x(k),z);
end
end

Use the fiaccel function to create a MEX function and accelerate the MATLAB code.

x = fi(rand(100,1),1,16,15);
fiaccel test_moving_average -args {x} -report

Compare the non-accelerated and accelerated code.

tic; avg = test_moving_average(x); toc       % Non-compiled version
tic; avg = test_moving_average_mex(x); toc   % Compiled version

Convert Floating-Point MATLAB Code to Fixed Point

Create a coder.FixptConfig object, fixptcfg, with default settings.

fixptcfg = coder.config('fixpt');

Set the test bench name. In this example, the test bench function name is dti_test.

fixptcfg.TestBenchName = 'dti_test';

Convert a floating-point MATLAB function to fixed-point MATLAB code. In this example, the MATLAB function name is dti.

fiaccel -float2fixed fixptcfg dti

Input Arguments

fcn — MATLAB function to generate MEX from

function name

MATLAB function to generate MEX from, specified as a function existing in the current working folder or on the path.

Note

If your top-level file is on a path that contains Unicode characters, code generation might not be able to find the file.

-options — Compiler options

option value | space delimited list of option values

Compiler options, specified as a space delimited list of option values. fiaccel gives precedence to individual command-line options over options specified using a configuration object. If command-line options conflict, the right-most option prevails.

Specified as one or more of these values:

-args example_inputs	Define the size, class, and complexity of MATLAB function inputs by providing a cell array of example input values. The position of the example input in the cell array must correspond to the position of the input argument in the MATLAB function definition. To generate a function that has fewer input arguments than the function definition has, omit the example values for the arguments that you do not want. Specify the example inputs immediately after the function to which they apply. Instead of an example value, you can provide a coder.Type object. To create a coder.Type object, use the coder.typeof function.
-config config_object	Specify MEX generation parameters, based on config_object, defined as a MATLAB variable using coder.mexconfig. For example: cfg = coder.mexconfig;
-d out_folder	Store generated files in the absolute or relative path specified by out_folder. If the folder specified by out_folder does not exist, fiaccel creates it for you. If you do not specify the folder location, fiaccel generates files in the default folder fiaccel/mex/fcn, where fcn is the name of the MATLAB function specified at the command line. The function does not support the following characters in folder names: asterisk (*), question-mark (?), dollar ($), and pound (#).
-float2fixed float2fixed_cfg_name	Generates fixed-point MATLAB code using the settings specified by the floating-point to fixed-point conversion configuration object named float2fixed_cfg_name. For this option, fiaccel generates files in the folder codegen/fcn_name/fixpt. You must set the TestBenchName property of float2fixed_cfg_name. For example: fixptcfg.TestBenchName = 'myadd_test'; specifies that myadd_test is the test file for the floating-point to fixed-point configuration object fixptcfg. You cannot use this option with the -global option.
-g	Compiles the MEX function in debug mode, with optimization turned off. If not specified, fiaccel generates the MEX function in optimized mode.
-global global_values	Specify initial values for global variables in MATLAB file. Use the values in cell array global_values to initialize global variables in the function you compile. The cell array should provide the name and initial value of each global variable. You must initialize global variables before compiling with fiaccel. If you do not provide initial values for global variables using the -global option, fiaccel checks for the variable in the MATLAB global workspace. If you do not supply an initial value, fiaccel generates an error. The generated MEX code and MATLAB each have their own copies of global data. To ensure consistency, you must synchronize their global data whenever the two interact. If you do not synchronize the data, their global variables might differ. You cannot use this option with the -float2fixed option.
-I include_path	Add include_path to the beginning of the code generation path. fiaccel searches the code generation path first when converting MATLAB code to MEX code.
-launchreport	Generate and open a code generation report. If you do not specify this option, fiaccel generates a report only if error or warning messages occur or you specify the -report option.
-nargout	Specify the number of output arguments in the generated entry-point function. The code generator produces the specified number of output arguments in the order in which they occur in the MATLAB function definition.
-o output_file_name	Generate the MEX function with the base name output_file_name plus a platform-specific extension. output_file_name can be a file name or include an existing path. If you do not specify an output file name, the base name is fcn_mex, which allows you to run the original MATLAB function and the MEX function and compare the results.
-O optimization_option	Optimize generated MEX code, based on the value of optimization_option: enable:inline — Enable function inlining disable:inline — Disable function inlining If not specified, fiaccel uses inlining for optimization.
-report	Generate a code generation report. If you do not specify this option, fiaccel generates a report only if error or warning messages occur or you specify the -launchreport option.
-?	Display help for fiaccel command.

Version History

Introduced in R2011a

R2023a: Change to default fiaccel behavior for constant inputs

When the fiaccel function generates a MEX file, it no longer automatically removes constants from the call to the MEX file. With this change, fiaccel and codegen MEX generation now have the same default behavior with respect to constant inputs.

fiaccel myfun -args {x,coder.Constant(c)}
myfun_mex(x,c)

To revert to the prior behavior, set the ConstantInputs property of the coder.MexConfig object to 'Remove'.

cfg = coder.MexConfig;
cfg.ConstantInputs = "Remove";
fiaccel myfun -args {x,coder.Constant(c)} -config cfg
myfun_mex(x)