Question

Does anyone know how the std::sqrt() function works? (or at least have an idea?)

I’ve seen methods on the internet that seemed really slow, using lots of approximations and iterations.

Everyone knows sqrt() function is slow, but I’d like to know how the one from std works so I could have a vague idea of when it is beneficial to avoid it. (yes, if I want to be sure I can profile, but it’s still nice to have a vague idea)

EDIT: Didn’t really formulate the question too well… What I’m interested in:

• how would the fastest C++ function calculating a square root look like? (more or less, I just want to know the actual logic behind it)

Answer 1

The standard does not specify a particular implementation.

One option is to look at a typical implementation, but you’ll probably find it’s heavily-optimised assembler.