Separate compilation units vs Single Compilation unit for faster compilation, linking, and optimised code?

Question

There are several questions which talk about why we should have separate compilation units so improve compile times (for example, not including any code in the hpp file,but only

Answer 1

If the question is about comparing one cpp including all cpps and one header file including all header files versus one cpp and multiple header files, then I don't think there will be a significant difference (or any at all).

Including all cpps in one file that is (and probably only that) what makes the difference. But this is a highly theoretical discussion with no real value. No one would ever do this in a project for the reasons all here have mentioned.

If you want to know what is going on under the hood, read this:

https://randomascii.wordpress.com/2014/03/22/make-vc-compiles-fast-through-parallel-compilation/