[tombert]

Yeah that’s not true. In fact I would say it’s almost the opposite; most things (other than IO) will go slower if you just throw extra threads at it.

There’s overhead with thread creation, locks can introduce a lot of contention and waiting and context switches, coordination between threads has a non-zero cost, and the list goes on.

Well-optimized multithreaded code will often be faster but thats harder than it sounds, and it’s certainly not the case that “single threading always makes it run slower”.