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Scale factor in opposite-color bishop endings

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This change varies the scale factor with the total number of pieces and pawns on the strongSide.

STC :
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 150920 W: 28828 L: 28422 D: 93670 +0.65 Elo
Ptnml(0-2): 2507, 17548, 35030, 17782, 2593
https://tests.stockfishchess.org/tests/view/5e983eb2c00499c5410f4951

LTC :
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 69238 W: 8810 L: 8446 D: 51982 +1.58 Elo
Ptnml(0-2): 451, 6276, 20879, 6484, 529
https://tests.stockfishchess.org/tests/view/5e985b27c00499c5410f4987

closes https://github.com/official-stockfish/Stockfish/pull/2637

Bench 4821332
This commit is contained in:
xoto10 2020-04-16 18:10:44 +01:00 • committed by Joost VandeVondele
parent 6f35af7ad3
commit ecac132bca
1 changed files with 9 additions and 4 deletions
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13
src/evaluate.cpp
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@ -761,11 +761,16 @@ namespace {
// If scale is not already specific, scale down the endgame via general heuristics
if (sf == SCALE_FACTOR_NORMAL)
{
if ( pos.opposite_bishops()
&& pos.non_pawn_material() == 2 * BishopValueMg)
sf = 22;
if (pos.opposite_bishops())
{
if ( pos.non_pawn_material(WHITE) == BishopValueMg
&& pos.non_pawn_material(BLACK) == BishopValueMg)
sf = 22;
else
sf = 22 + 3 * pos.count<ALL_PIECES>(strongSide);
}
else
sf = std::min(sf, 36 + (pos.opposite_bishops() ? 2 : 7) * pos.count<PAWN>(strongSide));
sf = std::min(sf, 36 + 7 * pos.count<PAWN>(strongSide));
sf = std::max(0, sf - (pos.rule50_count() - 12) / 4);
}