If all you ever deal with are what are known as "embarrassingly parallel" problems, where you don't need to do any synchronization or intermediate communication

If all you ever deal with are what are known as "embarrassingly parallel" problems, where you don't need to do any synchronization or intermediate communication between cores, then true parallelism isn't really needed and you can do whatever you were trying to do with simple process forking or something of that nature. Problems that are not embarrassingly parallel often require frequent and complicated communication and synchronization between cores. For this you need to use a real multi-threading library, or do some complicated message passing on a per-process level. If you need hundreds of workers, it is better to use something more light-weight than a thread, as Go does. Once crystal's parallelism support is added, it will have these light-weight "go-style" threads, so this complaint will disappear.