Author: Fawna Bergstrom
Date: 18:38:29 10/22/98
Go up one level in this thread
Well everyone has their opinions on this kind of question--here are a few of mine. Let's go back to basics: Level I: You search full-width to a fixed depth (alpha-beta, iterative deepening, etc. are all assumed, of course.) Here your evaluator includes both material and positional factors. Move ordering is critical. First expand "killer" moves, "interesting" moves and moves that yield a higher evaluation. Level II: If you like you can then search beyond that looking at "interesting" moves such as captures, threats, checks, etc. Don't bother with threats unless the threatened piece is hanging and/or more valuable than the threatening piece. You should limit the depth of this second phase or you can skip it altogether and go straight to level III--it's your call. In level II the evaluator adjusts for material only. Personally I wouldn't waste too many plies on Level II. Level III: Beyond that you MUST look at checks by a side that isn't winning, moves that get out of check by a side that isn't losing, and captures of a piece larger than the current material defecit, by a side that isn't winning. (For example, if it's White's move and she is a Knight down, look at a check or a rook capture but don't bother with any pawn captures. On the other hand, if it's White's move and she is already a rook up, then who cares if she can also capture the queen.) Examine large captures before smaller ones and checks last of all. This third phase has NO DEPTH LIMIT and adjusts for material only. Simple threats and other less-interesting moves are ignored in Level III. Of course, none of these issues will do you any good if your program is not super-efficient. When you hit a "wall" and can't make any more conceptual improvements, then throw away every line of code and write a new super-optimal version. Examine public-domain source code for ideas to improve efficiency. I liked your question--very interesting topic.
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