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Prevent code generator from creating function specializations for constant-size expressions

Since R2019b



coder.ignoreSize(expression) declares that the code generator must not use the constant size of an expression to create function specializations.


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If your MATLAB® code calls a function multiple times and passes inputs of different sizes, the code generator can create function specializations for each size. To avoid this issue, use coder.ignoreSize on the function input. For example, this code uses coder.ignoreSize to avoid creating multiple copies of the function indexOf:

function [out1, out2] = test1(in)
  a = 1:10;
  b = 2:40;
  % Without coder.ignoreSize duplicate functions are generated
  out1 = indexOf(coder.ignoreSize(a), in);
  out2 = indexOf(coder.ignoreSize(b), in);

function index = indexOf(array, value)
  for i = 1:numel(array)
      if array(i) == value
          index = i;
  index = -1;

To generate code, enter:

codegen test1 -config:lib -report -args {1}

Input Arguments

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Example: foo(coder.ignoreSize(1:10))

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.


  • If you assign an expression to a variable and declare the variable as variable-size by using coder.varsize, this declaration has the same effect as using coder.ignoreSize on the expression.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Version History

Introduced in R2019b