Manifold

Erlang and Elixir make it very easy to send messages between processes even across the network, but there are a few pitfalls. Sending a message to many PIDs across the network also copies the message across the network many times. Send calls cost about 70 µs/op so doing them in a loop eventually gets too expensive. Manifold distributes the work of sending messages to the remote nodes of the PIDs, which guarantees that the sending processes at most only calls send/2 equal to the number of involved remote nodes. Manifold does this by first grouping PIDs by their remote node and then sending to Manifold.Partitioner on each of those nodes. The partitioner then consistently hashes the PIDs using :erlang.phash2/2, groups them by the number of cores, sends to child workers, and finally those workers send to the actual PIDs. This ensures the partitioner does not get overloaded and still provides the linearizability guaranteed by send/2.