Actually, if the thread runtime maintains its own concept of time, the algorithm doesn't even need to sleep in real time. Once all the threads have been created, the thread runtime can notice that all threads are idle and that the next thread to be scheduled is the one at time N, so it can simply update the current time to N and start executing that thread. Repeat for each thread and you'll have your sorted array out without any sleeps.

After all, all the sorting work was already done when the threads started sleeping, having registered themselves with the orchestrator (timer wheel etc) that will eventually wake them up. Actually performing the sleep is not necessary.

I don't know about Haskell, but with Rust the tokio runtime lets you do this using start_paused ( https://docs.rs/tokio/latest/tokio/runtime/struct.Builder.ht... )