From 4c0299832555c3e35eb1f8779bedf7d1d2819cf1 Mon Sep 17 00:00:00 2001 From: Joost VandeVondele Date: Sat, 29 May 2021 15:44:57 +0200 Subject: [PATCH] Simplify NNUE / classical evaluation selection for the new network architecture these rules can be simplified, closer to the original PSQT difference based again. passed STC LLR: 2.94 (-2.94,2.94) <-2.50,0.50> Total: 22656 W: 1979 L: 1868 D: 18809 Ptnml(0-2): 70, 1496, 8087, 1603, 72 https://tests.stockfishchess.org/tests/view/60b24579db3c4776cb89d122 passed LTC LLR: 2.93 (-2.94,2.94) <-2.50,0.50> Total: 30224 W: 1015 L: 953 D: 28256 Ptnml(0-2): 4, 860, 13330, 906, 12 https://tests.stockfishchess.org/tests/view/60b27613db3c4776cb89d145 closes https://github.com/official-stockfish/Stockfish/pull/3511 Bench: 3937626 --- src/evaluate.cpp | 24 ++++-------------------- 1 file changed, 4 insertions(+), 20 deletions(-) diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 40c41a86..0e66fea6 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -218,7 +218,6 @@ namespace { constexpr Value LazyThreshold2 = Value(1102); constexpr Value SpaceThreshold = Value(11551); constexpr Value NNUEThreshold1 = Value(800); - constexpr Value NNUEThreshold2 = Value(176); // KingAttackWeights[PieceType] contains king attack weights by piece type constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 }; @@ -1127,29 +1126,14 @@ Value Eval::evaluate(const Position& pos) { return nnue; }; - // If there is PSQ imbalance we use the classical eval. We also introduce - // a small probability of using the classical eval when PSQ imbalance is small. + // If there is PSQ imbalance we use the classical eval. Value psq = Value(abs(eg_value(pos.psq_score()))); int r50 = 16 + pos.rule50_count(); bool largePsq = psq * 16 > (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50; - // Use classical evaluation for really low piece endgames. - // One critical case is the draw for bishop + A/H file pawn vs naked king. - bool lowPieceEndgame = pos.non_pawn_material() == BishopValueMg - || (pos.non_pawn_material() < 2 * RookValueMg && pos.count() < 2); - - v = largePsq || lowPieceEndgame ? Evaluation(pos).value() // classical - : adjusted_NNUE(); // NNUE - - // If the classical eval is small and imbalance large, use NNUE nevertheless. - // For the case of opposite colored bishops, switch to NNUE eval with small - // probability if the classical eval is less than the threshold. - if ( largePsq - && !lowPieceEndgame - && ( abs(v) * 16 < NNUEThreshold2 * r50 - || ( pos.opposite_bishops() - && abs(v) * 16 < (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50))) - v = adjusted_NNUE(); + v = largePsq ? Evaluation(pos).value() // classical + : adjusted_NNUE(); // NNUE + } // Damp down the evaluation linearly when shuffling -- 2.39.2