Category: Code

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MadChess 3.0 Beta 5c5d4fc (Piece Mobility)

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I have not worked on my chess engine in over a year. I had other, more important, priorities. In the last year, my wife and I bought a new home closer to the city, sold our old home, moved (*), started new jobs in the summer, and ran the Chicago Marathon in the autumn. The little free time I had for hobby programming I spent on general interest projects, not on MadChess. I’m especially proud of Leaderless Replication, an essay I published on my general programming blog, ErikTheCoder. Lately I’ve had time to do some chess programming. I added piece… Continue Reading

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MadChess 3.0 Beta Build 103 (Passed Pawns)

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I added passed pawn evaluation to MadChess 3.0 Beta. The passed pawn evaluation code scores the following features: Passed Pawns Free Passed Pawns (no pieces blocking promotion path) King Escorted Passed Pawns Unstoppable Passed Pawns (Rule of the Square) Middlegame Passed Pawns: 000 000 003 008 015 024 034 000 Endgame Passed Pawns: 000 004 018 042 075 118 170 000 Endgame Free Passed Pawns: 000 008 034 077 138 216 311 000 Endgame King Escorted Passed Pawn: 11 Unstoppable Passed Pawn: 775   This code improved the engine’s understanding of threats created by pushing passed pawns. It increased the… Continue Reading

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MadChess 3.0 Beta Build 093 (Staged Move Generation)

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I increased the speed at which MadChess 3.0 Beta examines nodes by implementing staged move generation. Previously, in the main search, the chess engine would generate all pseudo-legal moves, sort them by move priority, then iterate through them: testing move legality (does move expose own king to check) and playing the legal moves. This is wasteful if a beta cutoff occurs early in the move list. Usually a capture is responsible for a beta cutoff, so time is wasted generating non-captures. Now the chess engine generates moves in stages. I could have implemented more stages (QueenCaptures, RookCaptures, BishopKnightCaptures, etc) but… Continue Reading

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MadChess 3.0 Beta Build 084 (History Heuristics)

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I increased the playing strength of MadChess 3.0 by improving the history heuristics used by Late Move Reductions (LMR). First, I added a flag that indicates if a move was played during search (indicated below with “!”). This implies the move is legal (doesn’t expose own king to check) and search examined it (as opposed to moves appearing in the move list after a move that causes a beta cutoff). Moves are encoded as ulong primitives like so: Next, I altered the search function to flag played moves. Then I modified the search function so it not only increments move… Continue Reading

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MadChess 3.0 Beta Build 075 (Eval Param Tuning)

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I ported my particle swarm tuning code from MadChess 2.x to MadChess 3.0 Beta, then simplified and improved it. My code uses the Texel tuning technique described by Peter Österlund in a TalkChess forum post. I improved my particle swarm algorithm in the following manner. Simplified update of evaluation parameters via EvaluationConfig class. Run the Iterate method of each ParticleSwarm on the .NET Core threadpool instead of using dedicated threads. Locate global best particle (among all particle swarms) and update particle velocities after all Iterate methods have completed. This eliminates need to synchronize reads and writes of global state via… Continue Reading