opening book coding

[Edmund]

Storing statistics per move is always superior than storing it per position.

Eg.
1. e4 e5 2. Bb5 a6 3. Nf3

Most opening books that store per position statistics would play Nc6?? here, just because it sees the transposition into the spanish opening and doesn't know the position after axb5!

Requiring the current position to exist in the book before using book moves should fix this problem. In addition, storing statistics per position doesn't loose information for different moves that come to the same position.

right, this should solve the problem