From: Alain SAVARD Date: Tue, 8 May 2018 09:00:51 +0000 (+0200) Subject: Drop the lever condition for backwards X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;ds=sidebyside;h=6634f41ac9e76fe623dd36d312b6955ab2c66a4f;p=stockfish Drop the lever condition for backwards We can view the patch version as adding some "undermining bonus" for level pawns, when the defending side can not easily avoid the exchange by advancing her pawn. • Case 1) White b2,c3, Black a3,b3: Black is breaking through, b2 deserves a penalty • Case 2) White b2,c3, Black a3,c4: if b2xa3 then White ends up with a weak pawn on a3 and probably a weak pawn on c3 too. In either case, White can still not safely play b2-b3 and make a phalanx with c3, which is the essence of a backward pawn definition. Passed STC in SPRT[0, 4]: LLR: -2.96 (-2.94,2.94) [0.00,4.00] Total: 131169 W: 26523 L: 26199 D: 78447 http://tests.stockfishchess.org/tests/view/5aefa4d50ebc5902a409a151 ELO 1.19 [-0.38,2.88] (95%) Passed LTC in SPRT[-3, 1]: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 24824 W: 3732 L: 3617 D: 17475 http://tests.stockfishchess.org/tests/view/5af04d3f0ebc5902a88b2e55 ELO 1.27 [-1.21,3.70] (95%) Closes https://github.com/official-stockfish/Stockfish/pull/1584 How to continue from there? There were some promising tests a couple of months ago about adding a lever condition for king danger in evaluate.cpp, maybe it would be time to re-try this after all the recent changes in pawns.cpp Bench: 4773882 --- diff --git a/src/movepick.h b/src/movepick.h index 666cca36..b6e5620e 100644 --- a/src/movepick.h +++ b/src/movepick.h @@ -117,8 +117,14 @@ public: MovePicker(const MovePicker&) = delete; MovePicker& operator=(const MovePicker&) = delete; MovePicker(const Position&, Move, Value, const CapturePieceToHistory*); - MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, Square); - MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, const PieceToHistory**, Move, Move*); + MovePicker(const Position&, Move, Depth, const ButterflyHistory*, + const CapturePieceToHistory*, + Square); + MovePicker(const Position&, Move, Depth, const ButterflyHistory*, + const CapturePieceToHistory*, + const PieceToHistory**, + Move, + Move*); Move next_move(bool skipQuiets = false); private: diff --git a/src/pawns.cpp b/src/pawns.cpp index ca9c3023..8b997b60 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -118,8 +118,8 @@ namespace { // A pawn is backward when it is behind all pawns of the same color // on the adjacent files and cannot be safely advanced. - backward = !lever && !(ourPawns & pawn_attack_span(Them, s + Up)) - && (stoppers & (leverPush | (s + Up))); + backward = !(ourPawns & pawn_attack_span(Them, s + Up)) + && (stoppers & (leverPush | (s + Up))); // Passed pawns will be properly scored in evaluation because we need // full attack info to evaluate them. Include also not passed pawns @@ -223,7 +223,7 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) { Value safety = (ourPawns & file_bb(ksq)) ? Value(5) : Value(-5); - if ((shift(theirPawns) & (FileABB | FileHBB) & BlockRanks) & ksq) + if (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) safety += 374; File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));