MadChess 3.1 Beta 533e382 (Move Legality Performance Improvement)

I improved the performance of code that determines the legality of pseudo-legal moves. Previously, move legality was tested prior to playing a move. This consisted of playing a move (to test whether it exposed its own king to check and whether it delivered check on the enemy king), undoing the move, updating the “check” move property, then re-playing the move. Now a move is played, move legality and check is tested, and the Board.PlayMove method returns a (bool isLegal, bool deliversCheck) tuple.

The calling method (such as Search.GetDynamicScore or Search.GetQuietScore) then either 1) undoes the move (if illegal or futile) and continues to the next pseudo-legal move or 2) searches the resulting position.

In addition to move legality, I experimented with other performance improvements. None of these experiments succeeded except PR 33: Trust Move Capture Victim, which eliminated redundant calls to Position.GetPiece(Square square) in move generation and when playing moves.

Eliminating redundant double-playing of a move (to test move legality) during search increased the search speed of MadChess 3.1 Beta and produced a 36 Elo gain in playing strength.

 

Feature Category Date Commit1 WAC2 Elo Rating3 Improvement
Move Legality
Performance Improvement
Search 2022 Mar 18 533e382 289 2687 +36
Pawn Structure Evaluation 2022 Jan 11 d691b32 288 2651 +15
Threats Evaluation 2021 Oct 24 26e5323 289 2636 +7
Color-Agnostic Code Evaluation 2021 Sep 13 2b475bc 286 2629 +12
Singular Move Search 2021 Jun 14 0c601ea 290 2617 +13
Endgame Eval Scaling Evaluation 2021 Apr 08 4d22dec 286 2604 +12
Bishop Pair Evaluation 2021 Mar 14 2960ec9 285 2592 +22
Position Cache Optimization Search 2021 Feb 23 42d7702 286 2570 +8
Move Generation Optimization Search 2021 Feb 17 22002dc 287 2562 +12
PVS and Null Move Search 2021 Feb 09 f231dac 285 2550 +20
Remove Aspiration Windows Search 2020 Dec 20 4b7963b 290 2530 +9
Time Management Search 2020 Dec 19 d143bb5 286 2521 +8
Crash Bug Search 2020 Aug 29 2d855ec 288 2513 +0
King Safety Evaluation 2020 Aug 16 6794c89 288 2513 +63
Eval Param Tuning Evaluation 2020 Jul 23 bef88d5 283 2450 +30
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 commit (hash) or Subversion source code revision (integer)
  2. Win At Chess position test, 3 seconds per position
  3. Bullet chess, 2 min / game + 1 sec / move
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