Is it a good idea to use IEEE754 floating point NaN for values which are not set?

Question

Is it a good idea to use IEEE754 floating point NaN (not-a-number) for values which are undefined for non-mathematical reasons?

In our case they are not yet set beca

Answer 1

I think it is a bad idea in general. One thing to keep in mind is that most CPU treat Nan much slower then "usual" float. And it is hard to guarantee you will never have Nan in usual settings. My experience in numerical computing is that it often brings more trouble than it worths.

The right solution is to avoid encoding "absence of value" in the float, but to signal it in another way. That's not always practical, though, depending on your codebase.