问题
I am developing a chess game and at the moment I'm trying to implement a minimax algorithm. I haven't done this before, also the little i known about how to programmatically represent and implement the following evaluation function features(material, mobility, piece square table, centre control, trapped piece, king safety, tempo and pawn structure) is not quite clear to me (I will be grateful if someone can explain to me in detail). I have been able to assign values to each chess pieces, piece action values and a square table for each piece. The problem am having at the moment is how to generate Piece attacked and defended values which will be added or subtracted from the score. The idea here is that i want to reward the AI agent for protecting its pieces and penalize it for having the pieces attacked. thanks in advances.
回答1:
Each of the evaluation features you mentioned will take up compute time. As you may already be aware, playing strength of a chess engine comes from two sources:
- Search
- Evaluation
And both contend for the same valuable resource, compute time. Evaluation tends to be heuristics based and hence a bit fuzzy, whereas search tends to yield more concrete and relevant results. If you are starting to build an engine then I would recommend focusing on search while keeping evaluation basic (but not weak!). That way you will be able to tell exactly where something went wrong and hence avoid possible early disappointments. Moreover, popular engines like Stockfish also started out by first building a strong search algorithm.
If you've been patient enough to read this far, let me point you to two useful resources for evaluation:
- Chess Programming Wiki's evaluation page: This website is probably the best online resource for chess engine development in general.
- Link to a basic but not weak evaluation function: This is C# code. Unfortunately I can't find the original article that I based this evaluation on.
Hope it helps :)
回答2:
I think that you shouldn't include the computation on attack and defended pieces. That functionality is already taken into account by the minmax algorithm in a more efficient way.
A piece in under attack if at the following move the opponent can take it. If you try to evaluate this possibility in a static evaluation function you will get into troubles if you want to do it correctly. If my protected pawn is taken by the opponent queen that is not an issue. How do you take this into account? If my queen is taken by the opposite pawn but moving the pawn puts the king under attack?
These considerations are better managed by the minmax algorithm, not the evaluator. Consider that to know how many pieces you can eat/can be eaten, you should take into account all possible moves and you probably would spend the same time that would be used to go one level deeper in the minmax algorithm. Moreover that time is wasted if you later decide to indeed proceed one step further in the minmax.
来源：https://stackoverflow.com/questions/24710968/need-help-on-chess-game-evaluation-function