Let’s say I had a program in C# that did something computationally expensive, like encoding a list of WAV files into MP3s. Ordinarily I would encode the files one at a time, but let’s say I wanted the program to figure out how many CPU cores I had and spin up an encoding thread on each core. So, when I run the program on a quad core CPU, the program figures out it’s a quad core CPU, figures out there are four cores to work with, then spawns four threads for the encoding, each of which is running on its own separate CPU. How would I do this?
And would this be any different if the cores were spread out across multiple physical CPUs? As in, if I had a machine with two quad core CPUs on it, are there any special considerations or are the eight cores across the two dies considered equal in Windows?
Don’t bother doing that.
Instead use the Thread Pool. The thread pool is a mechanism (actually a class) of the framework that you can query for a new thread.
When you ask for a new thread it will either give you a new one or enqueue the work until a thread get freed. In that way the framework is in charge on deciding wether it should create more threads or not depending on the number of present CPUs.
Edit: In addition, as it has been already mentioned, the OS is in charge of distributing the threads among the different CPUs.