Documentation

coder.ignoreConst

Prevent use of constant value of expression for function specializations

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Syntax

coder.ignoreConst(expression)

Description

example

coder.ignoreConst(expression)prevents the code generator from using the constant value ofexpressionto createfunction specializations.coder.ignoreConst(expression)returns the value ofexpression.

Examples

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Usecoder.ignoreConstto prevent function specializations for a function that is called with constant values.

Write the functioncall_myfn, which callsmyfcn.

function[x, y] = call_myfcn(n)%#codegenx = myfcn(n,'mode1'); y = myfcn(n,'mode2');endfunctiony = myfcn (n,mode) coder.inline('never');ifstrcmp(mode,'mode1') y = n;elsey = -n;endend

Generate standalone C code. For example, generate a static library. Enable the code generation report.

codegen-config:libcall_myfcn-args{1}-report

In the code generation report, you see two function specializations forcall_myfcn.

The code generator createscall_myfcn>myfcn>1formodewith a value of'mode1'. It createscall_myfcn>myfcn>2formodewith a value of'mode2'.

In the generated C code, you see the specializationsmy_fcnandb_my_fcn.

static double b_myfcn(double n) { return -n; } static double myfcn(double n) { return n; }

To prevent the function specializations, instruct the code generator to ignore that values of themodeargument are constant.

function[x, y] = call_myfcn(n)%#codegenx = myfcn(n, coder.ignoreConst('mode1')); y = myfcn(n, coder.ignoreConst('mode2'));endfunctiony = myfcn (n,mode) coder.inline('never');ifstrcmp(mode,'mode1') y = n;elsey = -n;endend

Generate the C code.

codegen-config:libcall_myfcn-args{1}-report

In the code generation report, you do not see multiple function specializations.

In the generated C code, you see one function formy_fcn.

Input Arguments

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More About

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Function Specialization

Version of a function in which an input type, size, complexity, or value is customized for a particular invocation of the function.

Function specialization produces efficient C code at the expense of code duplication. The code generation report shows all MATLAB function specializations that the code generator creates. However, the specializations might not appear in the generated C/C++ code due to later transformations or optimizations.

Tips

  • For some recursive function calls, you can usecoder.ignoreConstto force run-time recursion. SeeForce Code Generator to Use Run-Time Recursion.

  • coder.ignoreConst(expression)prevents the code generator from using the constant value ofexpressionto create function specializations. It does not prevent other uses of the constant value during code generation.

See Also

Topics

Introduced in R2017a

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MATLAB Coder Documentation
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