B observe X and Y respectively, and want to compute a function f (X, Y) with zero error. To
achieve this, nodes A and B send messages to a relay node C at rates RA and RB
respectively. The relay C then broadcasts a message to A and B at rate RC to help them
compute f (X, Y) with zero error. We allow block coding, and study the region of rate-triples
(RA, RB, RC) that are feasible. The rate region is characterized in terms of graph coloring of …