20.4. Sending Messages to Other Actors

When a computation is divided among actors that concurrently work on parts of a problem, the results need to be gathered together. Actors could deposit results in a threadsafe data structure, such as a concurrent hash map, but the actor model discourages the use of shared data. Instead, an actor that has computed a result should send a message to another actor.

How does an actor know where to send the result? There are several design choices.