From 1f3bd968bb194a1f42af661cca9ec445c13978e8 Mon Sep 17 00:00:00 2001 From: SFisGOD Date: Wed, 8 Jul 2020 10:09:32 +0800 Subject: [PATCH 1/1] Introduce bad outpost penalty In some French games, Stockfish likes to bring the Knight to a bad outpost spot. This is evident in TCEC S18 Superfinal Game 63, where there is a Knight outpost on the queenside but is actually useless. Stockfish is effectively playing a piece down while holding ground against Leela's break on the kingside. This patch turns the +56 mg bonus for a Knight outpost into a -7 mg penalty if it satisfies the following conditions: * The outpost square is not on the CenterFiles (i.e. not on files C,D,E and F) * The knight is not attacking non pawn enemies. * The side where the outpost is located contains only few enemies, with a particular conditional_more_than_two() implementation Thank you to apospa...@gmail.com for bringing this to our attention and for providing insights. See https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/dEXNzSIBgZU Reference game: https://tcec-chess.com/#div=sf&game=63&season=18 Passed STC: LLR: 2.93 (-2.94,2.94) {-0.50,1.50} Total: 6960 W: 1454 L: 1247 D: 4259 Ptnml(0-2): 115, 739, 1610, 856, 160 https://tests.stockfishchess.org/tests/view/5f08221059f6f0353289477e Passed LTC: LLR: 2.98 (-2.94,2.94) {0.25,1.75} Total: 21440 W: 2767 L: 2543 D: 16130 Ptnml(0-2): 122, 1904, 6462, 2092, 140 https://tests.stockfishchess.org/tests/view/5f0838ed59f6f035328947a2 various related tests show strong test results, but so far no generalizations or simplifications of conditional_more_than_two() are found. See PR for details. closes https://github.com/official-stockfish/Stockfish/pull/2803 Bench: 4366686 --- src/bitboard.h | 7 +++++++ src/evaluate.cpp | 9 ++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/src/bitboard.h b/src/bitboard.h index afeb40ec..15ec4153 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -130,6 +130,13 @@ constexpr bool more_than_one(Bitboard b) { return b & (b - 1); } +/// Counts the occupation of the bitboard depending on the occupation of SQ_A1 +/// as in `b & (1ULL << SQ_A1) ? more_than_two(b) : more_than_one(b)` + +constexpr bool conditional_more_than_two(Bitboard b) { + return b & (b - 1) & (b - 2); +} + constexpr bool opposite_colors(Square s1, Square s2) { return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1; } diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 6f2dd69b..ca6ea5c4 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -134,6 +134,7 @@ namespace { }; // Assorted bonuses and penalties + constexpr Score BadOutpost = S( -7, 36); constexpr Score BishopOnKingRing = S( 24, 0); constexpr Score BishopPawns = S( 3, 7); constexpr Score BishopXRayPawns = S( 4, 5); @@ -310,7 +311,13 @@ namespace { { // Bonus if piece is on an outpost square or can reach one bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them); - if (bb & s) + if ( Pt == KNIGHT + && bb & s & ~CenterFiles + && !(b & pos.pieces(Them) & ~pos.pieces(PAWN)) + && !conditional_more_than_two( + pos.pieces(Them) & ~pos.pieces(PAWN) & (s & QueenSide ? QueenSide : KingSide))) + score += BadOutpost; + else if (bb & s) score += Outpost[Pt == BISHOP]; else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us)) score += ReachableOutpost; -- 2.39.2