MadChess 3.0 Beta 6f3d17a (Late Move Pruning)

I added late move pruning to MadChess 3.0 Beta. Quiet moves (not captures, pawn promotions, castling, or check) near the search horizon that are sorted near the bottom of the move list- in order words, “late” moves- are skipped. These moves are “late” because history heuristics have recorded few instances of them causing a beta cutoff. Most likely they are futile (they will not raise the score to alpha), so the engine doesn’t waste time searching them.

The search only examines two quiet moves immediately next to the search horizon, five quiet moves two ply from the horizon, up to 20 quiet moves five ply from the horizon. Actually, fewer quiet moves may be examined due to futility pruning conditions.

This code increased the playing strength of MadChess 3.0 Beta by 29 ELO.

 

Feature Category Date Rev1 WAC2 ELO Rating3 Improvement
Late Move Pruning Search 2020 Feb 08 6f3d17a 288 2420 +29
Piece Mobility Evaluation 2020 Feb 01 5c5d4fc 282 2391 +62
Passed Pawns Evaluation 2018 Dec 27 103 279 2329 +119
Staged Move Generation Search 2018 Dec 15 93 275 2210 +39
History Heuristics Search 2018 Dec 03 84 275 2171 +28
Eval Param Tuning Evaluation 2018 Nov 24 75 272 2143 +47
Sophisticated Search
Material and Piece Location
Baseline 2018 Nov 08 58 269 2096 0
  1. GitHub (hash) or Subversion (integer) source code revision
  2. Win At Chess position test, 3 seconds per position
  3. Bullet chess, 2 min / game + 1 sec / move
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