Eval: pawnless endgames

[eduherminio]

Naive, first implementation (fe5115f): return 0 in drawn and drawish endgamaes

Score of Lynx-eval-pawnless-endgames-2485-win-x64 vs Lynx 2483 - main: 1254 - 1394 - 1700  [0.484] 4348
...      Lynx-eval-pawnless-endgames-2485-win-x64 playing White: 857 - 462 - 855  [0.591] 2174
...      Lynx-eval-pawnless-endgames-2485-win-x64 playing Black: 397 - 932 - 845  [0.377] 2174
...      White vs Black: 1789 - 859 - 1700  [0.607] 4348
Elo difference: -11.2 +/- 8.1, LOS: 0.3 %, DrawRatio: 39.1 %
SPRT: llr -2.25 (-77.9%), lbound -2.25, ubound 2.89 - H0 was accepted

Decrease endgame score for those cases where draw isn't guaranteed

Score of Lynx-eval-pawnless-endgames-2488-win-x64 vs Lynx 2483 - main: 1203 - 1339 - 1760  [0.484] 4302
...      Lynx-eval-pawnless-endgames-2488-win-x64 playing White: 842 - 406 - 903  [0.601] 2151
...      Lynx-eval-pawnless-endgames-2488-win-x64 playing Black: 361 - 933 - 857  [0.367] 2151
...      White vs Black: 1775 - 767 - 1760  [0.617] 4302
Elo difference: -11.0 +/- 8.0, LOS: 0.3 %, DrawRatio: 40.9 %
SPRT: llr -2.26 (-78.2%), lbound -2.25, ubound 2.89 - H0 was accepted

Removing drawish results

Score of Lynx-eval-pawnless-endgames-2518-win-x64 vs Lynx 2516 - main: 6122 - 6364 - 7567  [0.494] 20053
...      Lynx-eval-pawnless-endgames-2518-win-x64 playing White: 4228 - 1984 - 3815  [0.612] 10027
...      Lynx-eval-pawnless-endgames-2518-win-x64 playing Black: 1894 - 4380 - 3752  [0.376] 10026
...      White vs Black: 8608 - 3878 - 7567  [0.618] 20053
Elo difference: -4.2 +/- 3.8, LOS: 1.5 %, DrawRatio: 37.7 %
SPRT: llr -2.26 (-78.1%), lbound -2.25, ubound 2.89 - H0 was accepted

Add early game phase check

Test  | eval/pawnless-endgames
Elo   | -1.70 +- 3.44 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | -2.29 (-2.25, 2.89) [0.00, 3.00]
Games | N: 24070 W: 7332 L: 7450 D: 9288
Penta | [941, 2807, 4609, 2785, 893]
https://openbench.lynx-chess.com/test/136/

Divide eg score by 2 in rook and piece vs rook case

8+0.08
Score of Lynx-eval-pawnless-endgames-2701-win-x64 vs Lynx 2700 - main: 14214 - 13811 - 17578  [0.504] 45603
...      Lynx-eval-pawnless-endgames-2701-win-x64 playing White: 9851 - 4156 - 8795  [0.625] 22802
...      Lynx-eval-pawnless-endgames-2701-win-x64 playing Black: 4363 - 9655 - 8783  [0.384] 22801
...      White vs Black: 19506 - 8519 - 17578  [0.620] 45603
Elo difference: 3.1 +/- 2.5, LOS: 99.2 %, DrawRatio: 38.5 %
SPRT: llr 2.9 (100.2%), lbound -2.25, ubound 2.89 - H1 was accepted

[eduherminio]

Superseded by #693