> I'm only storing one half-move per position, specifically the current player's best move. I use that for the "Show hint" feature. I think you are describing

> I'm only storing one half-move per position, specifically the current player's best move. I use that for the "Show hint" feature. I think you are describing B = 1 case. When is the B != 1 case used then? I also wonder why the reference board seems to have an obvious mistake (rooks in place of bishops). Again, I hardly know any chess, so that might be my oversight and that does improve the compression for this particular data set.