How can you get number of PHYSICAL CPU cores using code?

Question

I'm using c++ but any programming language that solves this would be great.

Logical cores != physical cores because of Intel's hyperthreading and AMD's Simultaneous Multi Threading (SMT). Getting the logical core count is easy enough. Even browser-based JavaScript can get it with navigator.hardwareConcurrency. That's why I'm asking specifically about PHYSICAL cores.

Here is a very similar question but the answers are all obsolete and don't work. Some answers are one-liners but retrieve "Logical" not "Physical" cores:
https://stackoverflow.com/questions/2901694/how-to-detect-the-number-of-physical-processors-cores-on-windows-mac-and-linu

Here is a similar question asking for a JavaScript solution but none of the answers work for "Physical" cores.
https://stackoverflow.com/questions/3289465/get-number-of-cpu-cores-in-javascript

I want to get this value to help a program find the best number of threads to use without pushing the OS and CPU into wasteful timeslicing and context switching. Running as many CPU-bound threads as there are logical cores performs slightly worse than matching the number of physical cores.

Answer 1

Since nobody has answered yet..

The winapi has what you are searching: https://docs.microsoft.com/de-de/windows/win32/api/sysinfoapi/nf-sysinfoapi-getlogicalprocessorinformation

Check their code example below for how to access the physical(?) number of cores. I'm not sure what physical means these days.

Answer 2

Python has a library called psutil - in it there's a function called cpu_count which checks for logical ones by default, so:

psutil.cpu_count(logical=False)

Should output what you're looking for..? Hope it helps!

https://psutil.readthedocs.io/en/latest/#psutil.cpu_count

If you need the output I'm pretty sure you can run the .py with commands and retrieve the result with c++