Hardcoded Integers in C code generated by Matlab Coder

x = A\B

was converted to C code using Matlab coder. There are few lines in the generated code with hard coded integers. Like..

if (rankR <= 1.4903363393874656E-8)
// Some internal function calls
else
// Usage of standard sqrt

or

500.0 * fabs(A[0]) * 2.2206044429501313E-16

What is the purpose of these hard coded integers ? How are they useful for left matrix division ?

[Adam]

I would imagine they are 'epsilon' type parameters that are there to catch situations where you would end up dividing by zero or doing similarly ill-defined operations.

[Sean de Wolski]

Adam, that should be an answer!

format long
>> eps
ans =
   2.220446049250313e-16
>>

[Adam]

Done!

Answer 1

[Adam]

I would imagine they are 'epsilon' type parameters that are there to catch situations where you would end up dividing by zero or doing similarly ill-defined operations.

I've not seen the output of Matlab Coder myself yet though we do use it where I work, I just stay on the research end in Matlab itself personally.

By preference though I don't like seeing 'magic' numbers in code like that so I agree with your asking of the question because it is the type of question that magic numbers always throw up.

Nowadays I will always put a named constant in my file and use that instead.