Q:

What is the accuracy of erf in Visual Studio MSVC?

I need to use the erf function in my code, and a standard implementation is included in <cmath>. It's important for me to know the accuracy of the result. Does anyone know how it is implemented there (what algorithm or approximation)?
I'm using Visual Studio if that makes a difference.
Edit: This is not a duplicate of this question, since I want to know the precision of the implementation I'm using (MS Visual Studio), and the related question only says that the answer is implementation-specific.

A:

Since you are looking specifically for MSVC implementation-defined behavior, the place to go is the MSVC documentation:

These functions are implemented to balance performance with correctness. Because producing the correctly rounded result may be prohibitively expensive, these functions are designed to efficiently produce a close approximation to the correctly rounded result. In most cases, the result produced is within +/-1 ulp of the correctly rounded result, though there may be cases where there is greater inaccuracy. 

