An Evaluation Hash Table may be used in a similar fashion as a transposition table, that is using Zobrist or BCH hashing, to cache various computational expensive positional evaluation scores and flags.

• Despite the fact that the transposition table entries may contain evaluation scores as well, a tighter, dedicated evaluation hash table with its own replacement policy may gain a considerable amount of additional hits.

What sizes should these have?

• The UCI protocol comes with a command where the hash size can be set.

Since the pawn structure changes very rarely it should be a nice boost as long as it gets implemented smoothly.

Needs to store information about passed pawns so we do not have to find them every time.

The zobrist key for the pawns will have to be updated every time a pawn is moved, and also the current pawn evaluation uses the king positions as well.