From 421867ea2d62222d3656696c09a9c0c31bc98048 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Sun, 22 Aug 2010 14:18:58 +0100 Subject: [PATCH] Retire trapped bishop evaluation Another 100 lines of dubious and ad-hoc code. After 7644 games on russian cluster: Mod - Orig 1285 - 1249 - 5110 ELO +1 (+- 3.2) Signed-off-by: Marco Costalba --- src/evaluate.cpp | 98 ------------------------------------------------ 1 file changed, 98 deletions(-) diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 375c2369..e64dfa23 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -159,27 +159,6 @@ namespace { // right to castle. const Value TrappedRookPenalty = Value(180); - // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by - // enemy pawns. - const Score TrappedBishopA7H7Penalty = make_score(300, 300); - - // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black) - const Bitboard MaskA7H7[2] = { - ((1ULL << SQ_A7) | (1ULL << SQ_H7)), - ((1ULL << SQ_A2) | (1ULL << SQ_H2)) - }; - - // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by - // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only - // happen in Chess960 games. - const Score TrappedBishopA1H1Penalty = make_score(100, 100); - - // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black) - const Bitboard MaskA1H1[2] = { - ((1ULL << SQ_A1) | (1ULL << SQ_H1)), - ((1ULL << SQ_A8) | (1ULL << SQ_H8)) - }; - // The SpaceMask[color] contains the area of the board which is considered // by the space evaluation. In the middle game, each side is given a bonus // based on how many squares inside this area are safe and available for @@ -251,8 +230,6 @@ namespace { template void evaluate_passed_pawns(const Position& pos, EvalInfo& ei); - void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei); - void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei); inline Score apply_weight(Score v, Score weight); Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]); Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight); @@ -559,17 +536,6 @@ namespace { if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us)) evaluate_outposts(pos, ei, s); - // Special patterns: trapped bishops on a7/h7/a2/h2 - // and trapped bishops on a1/h1/a8/h8 in Chess960. - if (Piece == BISHOP) - { - if (bit_is_set(MaskA7H7[Us], s)) - evaluate_trapped_bishop_a7h7(pos, s, Us, ei); - - if (Chess960 && bit_is_set(MaskA1H1[Us], s)) - evaluate_trapped_bishop_a1h1(pos, s, Us, ei); - } - // Queen or rook on 7th rank if ( (Piece == ROOK || Piece == QUEEN) && relative_rank(Us, s) == RANK_7 @@ -865,70 +831,6 @@ namespace { } - // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7 - // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty - // if it is. - - void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) { - - assert(square_is_ok(s)); - assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP)); - - Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6); - Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8); - - if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN) - && pos.see(s, b6) < 0 - && pos.see(s, b8) < 0) - { - ei.value -= Sign[us] * TrappedBishopA7H7Penalty; - } - } - - - // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1 - // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for - // black), and assigns a penalty if it is. This pattern can obviously - // only occur in Chess960 games. - - void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) { - - Piece pawn = piece_of_color_and_type(us, PAWN); - Square b2, b3, c3; - - assert(Chess960); - assert(square_is_ok(s)); - assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP)); - - if (square_file(s) == FILE_A) - { - b2 = relative_square(us, SQ_B2); - b3 = relative_square(us, SQ_B3); - c3 = relative_square(us, SQ_C3); - } - else - { - b2 = relative_square(us, SQ_G2); - b3 = relative_square(us, SQ_G3); - c3 = relative_square(us, SQ_F3); - } - - if (pos.piece_on(b2) == pawn) - { - Score penalty; - - if (!pos.square_is_empty(b3)) - penalty = 2 * TrappedBishopA1H1Penalty; - else if (pos.piece_on(c3) == pawn) - penalty = TrappedBishopA1H1Penalty; - else - penalty = TrappedBishopA1H1Penalty / 2; - - ei.value -= Sign[us] * penalty; - } - } - - // evaluate_space() computes the space evaluation for a given side. The // space evaluation is a simple bonus based on the number of safe squares // available for minor pieces on the central four files on ranks 2--4. Safe -- 2.39.2