How to define lower limit at while code generation?

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Hi,
I am trying to generate C++ code for my function with Codegen. It has variable data size but has limits,min 100, max 1000. I know I can define upto limit but is it possible to define down limit?
Thanks for your help,

Accepted Answer

Ryan Livingston
Ryan Livingston on 24 Nov 2021
There is unfortunately no way to define a lower bound for a size. In this case, if you define the upper bound, Coder will assume the size could be anything up to that bound.
  2 Comments
Ryan Livingston
Ryan Livingston on 2 Dec 2021
That fixed size approach could work. In some cases you can also give value range hints to MATLAB Coder by using MATLAB assert to prune dead code. This may help but isn't a guarantee. For example
function y = foo(x)
t = zeros(x);
s = size(t,1);
assert(s > 100);
if s < 100
y = 1;
else
y = -1;
end
end
>> codegen foo -args 1 -config:lib -report
generates
double foo(double x)
{
(void)x;
return -1.0;
}
So you can use assert to give hints near the usage of the size lower bound. Since you can't specify lower bounds on the matrix size, the assert needs to be based on a variable whose value is the size rather than doing assert(size(t,1) > 100).
I'll give the warning that these asserts are hints which may or may not result in code optimization based on Coder heuristics. They can be useful but I'd warn against going down a rabbit hole without direct evidence of benefit in your use case.

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