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.

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