The Schedulers.computation() is probably the most useful scheduler for programmers. It provides us with a bounded thread-pool, which can contain a number of threads equal to the number of available CPU cores. As the name suggests, this scheduler is meant for CPU intense works.

We should use this scheduler only for CPU—intense tasks and not for any other cause. The reason is that the threads in this scheduler keeps the CPU cores busy, and may slow down the entire application if it is used for I/O bound or any other tasks that involves non-computational tasks.

The main reason why we should consider Schedulers.io() for I/O bound tasks and Schedulers.computation() for computational purposes is that computation() threads utilize the processors better and create no more threads than the available CPU cores, and reuses them. While Schedulers.io() is unbounded, and if you schedule 10,000 computational tasks on io() in parallel, then each of those 10,000 tasks each have their own thread and be competing for CPU incurring context switching costs.