From 320630ca1ab2792c31604ceca3e052159699b9b8 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Sun, 22 Mar 2009 13:55:08 +0100 Subject: [PATCH 1/1] Merge new pawn storm evaluation More accuracy in pawn storm evaluation directly from iPhone Glaurung. Signed-off-by: Marco Costalba --- src/pawns.cpp | 115 +++++++++++++++++++++++++++----------------------- 1 file changed, 63 insertions(+), 52 deletions(-) diff --git a/src/pawns.cpp b/src/pawns.cpp index 8dfb75a9..b9d112f0 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -120,14 +120,12 @@ namespace { 0, 0, 0, 0, 0, 0, 0, 0 }; - // Pawn storm open file bonuses by file: - const int KStormOpenFileBonus[8] = { - 45, 45, 30, 0, 0, 0, 0, 0 - }; + // Pawn storm open file bonuses by file + const int KStormOpenFileBonus[8] = { 45, 45, 30, 0, 0, 0, 0, 0 }; + const int QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 30, 45, 30 }; - const int QStormOpenFileBonus[8] = { - 0, 0, 0, 0, 0, 30, 45, 30 - }; + // Pawn storm lever bonuses by file + const int StormLeverBonus[8] = { 20, 20, 10, 0, 0, 10, 20, 20 }; } @@ -200,6 +198,7 @@ PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) { Bitboard ourPawns = pos.pawns(us); Bitboard theirPawns = pos.pawns(them); Bitboard pawns = ourPawns; + int bonus; // Initialize pawn storm scores by giving bonuses for open files for (File f = FILE_A; f <= FILE_H; f++) @@ -227,54 +226,66 @@ PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) { isolated = pos.pawn_is_isolated(us, s); doubled = pos.pawn_is_doubled(us, s); - // We calculate kingside and queenside pawn storm scores - // for both colors. These are used when evaluating middle - // game positions with opposite side castling. + // We calculate kingside and queenside pawn storm + // scores for both colors. These are used when evaluating + // middle game positions with opposite side castling. // // Each pawn is given a base score given by a piece square table - // (KStormTable[] or QStormTable[]). This score is increased if - // there are enemy pawns on adjacent files in front of the pawn. - // This is because we want to be able to open files against the - // enemy king, and to avoid blocking the pawn structure (e.g. white - // pawns on h6, g5, black pawns on h7, g6, f7). - - // Kingside and queenside pawn storms - int KBonus = KStormTable[relative_square(us, s)]; - int QBonus = QStormTable[relative_square(us, s)]; - bool outPostFlag = (KBonus > 0 && (outpost_mask(us, s) & theirPawns)); - bool passedFlag = (QBonus > 0 && (passed_pawn_mask(us, s) & theirPawns)); - - switch (f) { - - case FILE_A: - QBonus += passedFlag * QBonus / 2; - break; - - case FILE_B: - QBonus += passedFlag * (QBonus / 2 + QBonus / 4); - break; - - case FILE_C: - QBonus += passedFlag * QBonus / 2; - break; - - case FILE_F: - KBonus += outPostFlag * KBonus / 4; - break; - - case FILE_G: - KBonus += outPostFlag * (KBonus / 2 + KBonus / 4); - break; - - case FILE_H: - KBonus += outPostFlag * KBonus / 2; - break; - - default: - break; + // (KStormTable[] or QStormTable[]). Pawns which seem to have good + // chances of creating an open file by exchanging itself against an + // enemy pawn on an adjacent file gets an additional bonus. + + // Kingside pawn storms + bonus = KStormTable[relative_square(us, s)]; + if (f >= FILE_F) + { + Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB); + while (b) + { + Square s2 = pop_1st_bit(&b); + if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) + { + // The enemy pawn has no pawn beside itself, which makes it + // particularly vulnerable. Big bonus, especially against a + // weakness on the rook file. + if (square_file(s2) == FILE_H) + bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2); + else + bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2); + } else + // There is at least one enemy pawn beside the enemy pawn we look + // at, which means that the pawn has somewhat better chances of + // defending itself by advancing. Smaller bonus. + bonus += StormLeverBonus[f] - 2*square_distance(s, s2); + } + } + pi->ksStormValue[us] += bonus; + + // Queenside pawn storms + bonus = QStormTable[relative_square(us, s)]; + if (f <= FILE_C) + { + Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB); + while (b) + { + Square s2 = pop_1st_bit(&b); + if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) + { + // The enemy pawn has no pawn beside itself, which makes it + // particularly vulnerable. Big bonus, especially against a + // weakness on the rook file. + if (square_file(s2) == FILE_A) + bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2); + else + bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2); + } else + // There is at least one enemy pawn beside the enemy pawn we look + // at, which means that the pawn has somewhat better chances of + // defending itself by advancing. Smaller bonus. + bonus += StormLeverBonus[f] - 4*square_distance(s, s2); + } } - pi->ksStormValue[us] += KBonus; - pi->qsStormValue[us] += QBonus; + pi->qsStormValue[us] += bonus; // Member of a pawn chain (but not the backward one)? We could speed up // the test a little by introducing an array of masks indexed by color -- 2.39.2