[ketralnis]

That's true if all operations and intermediate states must be determistic, but if instead you only need some things to be deterministic then the cost is a lot lower. For instance, if you spawn a bunch of threads and join in them in the same order they were created, the order of the results you gather from them can be always be the same even if they didn't complete in the same order. The computation phase didn't pay any synchronization cost, but the gathering phase did