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
Feature Category Date Build Number WAC1 ELO Rating2 Improvement
Free Passed Pawns Evaluation 2015 Mar 10 59 270 2224 +31
Unstoppable Pawns
Draws, Material Trades
Evaluation 2015 Jan 31 52 270 2193 +39
Late Move Pruning Search 2015 Jan 10 44 273 2154 +39
History Heuristic
Late Move Reductions
Search 2015 Jan 04 43 275 2115 +50
Killer Moves Search 2015 Jan 03 38 275 2065 +61
Futility Pruning Search 2014 Dec 29 37 256 2004 +54
Null Move
Quiescence Recaptures
Search 2014 Dec 28 35 242 1950 +46
King Safety Evaluation 2014 Dec 24 32 225 1904 +27
Piece Mobility Evaluation 2014 Dec 16 29 225 1877 +64
Draw By Repetition Bug Evaluation 2014 Dec 10 27 225 1813 +47
Passed Pawns Evaluation 2014 Dec 09 26 225 1766 +72
Time Management Search 2014 Dec 08 25 231 1694 +24
Delay Move Generation
Aspiration Window Bug
Search 2014 Dec 02 23 231 1670 +44
MVV / LVA Move Order
Draw By Insufficient Material
Move List Overflow Bug
Search 2014 Dec 01 22 235 1626 +30
Tapered Evaluation
MG and EG Piece Location
Evaluation 2014 Nov 29 21 234 1596 +107
Alpha / Beta Negamax
Aspiration Windows
Quiescence, Hash
Material, Piece Squares
Baseline 2014 Nov 25 20 236 1489
  1. Win At Chess position test, 3 seconds per position
  2. Bullet chess, 2 min / game + 1 sec / move
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