MadChess 2.0 Beta Build 021 (Tapered Evaluation)

I added tapered evaluation to MadChess 2.0 Beta. The evaluation assigns a material score, a middlegame piece location score, and an endgame piece location score. Then calculates the game phase and returns a weighted average of the middlegame and endgame scores.

By separating piece location scores into middlegame and endgame phases, I can encourage MadChess to hold its queen back during the middlegame, and bring its king to the center during the endgame, for example.

	private const int _minorPhaseMaterial = 1;
	private const int _rookPhaseMaterial = 1;
	private const int _queenPhaseMaterial = 2;
	_openingPhaseMaterial = (8 * _minorPhaseMaterial) + (4 * _rookPhaseMaterial) + (2 * _queenPhaseMaterial);
	// Determine phase.
	int phaseMaterial = _minorPhaseMaterial * (_whiteKnights + _whiteBishops + _blackKnights + _blackBishops);
	phaseMaterial += _rookPhaseMaterial * (_whiteRooks + _blackRooks);
	phaseMaterial += _queenPhaseMaterial * (_whiteQueens + _blackQueens);
	_middlegamePercent = Math.Min((100 * phaseMaterial) / _openingPhaseMaterial, 100);
	int endgamePercent = 100 - _middlegamePercent;
	int middlegameScore = materialScore + mgLocationScore;
	int endgameScore = materialScore + egLocationScore;
	int staticScore = ((middlegameScore * _middlegamePercent) + (endgameScore * endgamePercent)) / 100;
	return _board.CurrentPosition.WhiteMove ? staticScore : -staticScore;

view raw TaperedEvaluation.cs hosted with by GitHub

This added 107 Elo to the playing strength of MadChess 2.0 Beta.

MadChess 2.0                   1596 :    800 (+42,=72,-686),   9.8 %

vs.                                 :  games (  +,  =,   -),   (%) :   Diff,  SD, CFS (%)
BikJump v2.01                       :    100 (  0,  2,  98),   1.0 :   -490,  18,    0.0
Matheus-2.3                         :    100 (  3, 10,  87),   8.0 :   -467,  17,    0.0
Monarch 1.7                         :    100 (  2,  2,  96),   3.0 :   -446,  18,    0.0
BigLion 2.23w                       :    100 (  5, 11,  84),  10.5 :   -413,  17,    0.0
Faile 1.4                           :    100 (  7, 10,  83),  12.0 :   -404,  16,    0.0
Sharper 0.17                        :    100 (  4,  9,  87),   8.5 :   -396,  17,    0.0
Jabba13032012                       :    100 (  7, 12,  81),  13.0 :   -337,  17,    0.0
Roce 0.0390                         :    100 ( 14, 16,  70),  22.0 :   -258,  16,    0.0

1. Subversion source code revision
2. Win At Chess position test, 3 seconds per position
3. Bullet chess, 2 min / game + 1 sec / move