Recency: Newer games contribute more to weights than older ones.

[Jonathan003]

Can you please add an option for Recency for calculating the book move weights.
If a move is out of fashion in the input pgn file, it most of the time has a good reason.

[likeawizard]

I'll have look and think. But my initial reaction is - no, the polyglot format has a very specific meaning for the weights and that is purely based on the outcomes of the games win +2, draw +1 and moves for lost games are not included. I do not think tinkering with these weights is a good idea and breaking the expectation that the format is built on.

In that case I would probably suggest filtering games from the PGN file itself before composing a book. And I of course wan't to find the time to touch up possible filters which would exclude games from being added to the book.

[Jonathan003]

Filtering out older games from the PGN before composing a book is a good plan but only if there is an alternative more recent game.