Optimal number of threads per core

Question

Let\'s say I have a 4-core CPU, and I want to run some process in the minimum amount of time. The process is ideally parallelizable, so I can run chunks of it on an infinite

Answer 1

The actual performance will depend on how much voluntary yielding each thread will do. For example, if the threads do NO I/O at all and use no system services (i.e. they're 100% cpu-bound) then 1 thread per core is the optimal. If the threads do anything that requires waiting, then you'll have to experiment to determine the optimal number of threads. 4000 threads would incur significant scheduling overhead, so that's probably not optimal either.