MadChess 2.0 Beta Build 059 (Free Passed Pawns)

I added free passed pawn evaluation to MadChess 2.0 Beta. Unobstructed passed pawns on the sixth or seventh rank are awarded a bonus if they may advance to the next square without material loss. The square must be unoccupied and the score after exchanging pieces on the advance square must not be negative.

In addition, I simplified the move ordering code. I felt the GetNextMove() method required too much external bookkeeping (to mark played moves, illegal moves, update local move variable, save move back to array, etc) and therefore was too prone to bugs. I replaced it with a two stage sort and a simple for loop. First, the four highest priority moves are identified. If the fifth move is reached, the remaining moves are sorted. This avoids the cost of sorting all moves in 90% of the cases where a cutoff occurs in the first few moves. The two stage sort performed as well as the GetNextMove() technique.

This added 31 Elo to the playing strength of MadChess 2.0 Beta.

MadChess 2.0                   2224 :    800 (+439,=151,-210),  64.3 %

vs.                                 :  games (   +,   =,   -),   (%) :   Diff,  SD, CFS (%)
Glass 1.6                           :     50 (   4,   9,  37),  17.0 :   -196,  25,    0.0
Sungorus 1.4                        :     50 (  19,   9,  22),  47.0 :    -86,  12,    0.0
FireFly v2.6.0                      :     50 (  25,  11,  14),  61.0 :    +21,  14,   93.6
ZCT 0.3.2450                        :     50 (  20,  12,  18),  52.0 :    +23,  14,   95.4
Jazz v444                           :     50 (  25,  10,  15),  60.0 :    +43,  13,  100.0
Beowulf 2.4                         :     50 (  23,   9,  18),  55.0 :    +58,  19,   99.9
Wing 2.0                            :     50 (  24,  18,   8),  66.0 :   +108,  15,  100.0
BikJump v2.01                       :     50 (  17,  16,  17),  50.0 :   +123,  13,  100.0
Brainless 1.0                       :     50 (  33,   6,  11),  72.0 :   +125,  19,  100.0
Matheus-2.3                         :     50 (  27,  10,  13),  64.0 :   +148,  12,  100.0
Monarch 1.7                         :     50 (  29,  12,   9),  70.0 :   +175,  15,  100.0
BigLion 2.23w                       :     50 (  34,   6,  10),  74.0 :   +201,  13,  100.0
Sharper 0.17                        :     50 (  38,   6,   6),  82.0 :   +217,  13,  100.0
Faile 1.4                           :     50 (  37,   8,   5),  82.0 :   +244,  12,  100.0
Jabba13032012                       :     50 (  42,   4,   4),  88.0 :   +275,  12,  100.0
Roce 0.0390                         :     50 (  42,   5,   3),  89.0 :   +344,  13,  100.0

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