[howerj]

I am not sure what you mean by concurrent in this case, muxleq is just subleq with one extra instruction. The extra instruction is based off of multiplexing (see https://en.wikipedia.org/wiki/Multiplexer). Subleq as you know is incredibly inefficient, muxleq is an experiment to add a single instruction to Subleq in order to greatly improve its efficiency.

The `mux` instruction added computes:

   m[operand2] = (m[operand1] & ~selector) | (m[operand2] & selector)

As multiplexing is a universal gate (so long as you have access to true and false as constants) you can use this to calculate AND/OR/XOR, which are very expensive to do in a pure Subleq machine. It also means you can do a MOV in a single instruction instead of four (set the `selector` to zero in this case). This in turns speeds up indirect loads and stores.