Decrease slightly the penalty for opponent king distance to passed pawn.
Instead of 5:2 ratio (or 20:8) we now have 19:8
STC
http://tests.stockfishchess.org/tests/view/
5de281b2727dc1d26718a673
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 28638 W: 6297 L: 6104 D: 16237
LTC
http://tests.stockfishchess.org/tests/view/
5de2a2ff727dc1d26718a67b
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 59586 W: 9766 L: 9429 D: 40391
Where to go from here:
Further tests will try a similar tweak on the friendly king proximity penalty,
because recent experiments indicate that this penalty is quite sensitive,
but I wanted to try first on the larger term.
Closes https://github.com/official-stockfish/Stockfish/pull/2435
bench:
5258928
---------------
Increasing the penalty ratio to 21:8 was neutral.
http://tests.stockfishchess.org/tests/view/
5de2814d727dc1d26718a671
Decreasing the penalty ratio a bit more to 9:4 seems less promising
http://tests.stockfishchess.org/tests/view/
5de2f4c2727dc1d26718a691
http://tests.stockfishchess.org/tests/view/
5de32ecc727dc1d26718a6b0
Square blockSq = s + Up;
// Adjust bonus based on the king's proximity
- bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
- - king_proximity(Us, blockSq) * 2) * w);
+ bonus += make_score(0, ( (king_proximity(Them, blockSq) * 19) / 4
+ - king_proximity(Us, blockSq) * 2) * w);
// If blockSq is not the queening square then consider also a second push
if (r != RANK_7)