MadChess 3.0 Beta 4d22dec (Endgame Eval Scaling)

I improved MadChess 3.0 Beta’s detection of drawn endgames. The IsPawnlessDraw method scores the following positions as drawn. Though it continues to search moves for a swindle (opponent mistake that makes a drawn game winnable). 2N vrs <= 1 Minor Q vrs 2B Q vrs 2N Q vrs Q Q vrs R + Minor R vrs R + <= 1 Minor Q vrs 2R 2R vrs R + Minor 2R vrs 2R Testing revealed considering R vrs <= 2 Minors a draw increased evaluation error and caused the engine to play weaker. I left that endgame in the IsPawnlessDraw function… Continue Reading

MadChess 2.0 Beta Build 052 (Unstoppable Pawns, Draws, Material Trades)

I added code to detect unstoppable passed pawns and drawn endgames, and code to evaluate material trades. The code that evaluates material trades implements the age old advice, “When ahead trade pieces. When behind trade pawns.” A greater bonus is giving for trading pawns, since in many endgames the side with a material advantage cannot win without promoting a pawn. This added 39 Elo to the playing strength of MadChess 2.0 Beta. MadChess 2.0 2193 : 800 (+399,=168,-233), 60.4 % vs. : games ( +, =, -), (%) : Diff, SD, CFS (%) Glass 1.6 : 50 ( 4, 7,… Continue Reading

MadChess 2.0 Beta Build 027 (Draw By Repetition Bug)

Yes! I found and exterminated the bug I mentioned in my previous post. I corrected a bug that caused MadChess to play a losing move in a drawn by repetition position. MadChess evaluates the first repetition of a position as drawn, even though the rules of chess state the second repetition is drawn. This search optimization avoids wasting a ply to determine the position is drawn by repetition. MadChess’ recursive search method checks if a position is repeated before searching any moves. If the position is a repeat of an earlier position, the search returns a zero score. I forgot… Continue Reading