20180117 - Localized Message Broadcast
One possible way to support localized message broadcast would be to add a "mask" and convert node "address" into "offset".
For example for a 1024 node machine, message packets would contain,
10-bit node offset
10-bit node mask
N-bit data packet
A leaf node can check if they should accept the packet if the following is true: (node - offset) & mask
Which enables power-of-2 sized N-dimensional broadcast with non-aligned offset.
A non-leaf node just needs to check only a subset of bits to see if any child node needs a given packet.