X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=795e31e2423941a3a973187d83c2d2b080b353c8;hb=0049d3f337b6f3a66a0;hp=cec9aba142af22fcf96edf82879ef8da7f190fa8;hpb=5bed82cd4e34c329bd08c57963ccc93c15ca0f05;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
index cec9aba1..795e31e2 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -1,7 +1,7 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -17,46 +17,38 @@
along with this program. If not, see .
*/
-
-////
-//// Includes
-////
-
#include
-#include
+#include "bitboard.h"
#include "bitcount.h"
#include "pawns.h"
#include "position.h"
-
-////
-//// Local definitions
-////
-
namespace {
- /// Constants and variables
-
+ #define V Value
#define S(mg, eg) make_score(mg, eg)
- // Doubled pawn penalty by file
- const Score DoubledPawnPenalty[8] = {
- S(13, 43), S(20, 48), S(23, 48), S(23, 48),
- S(23, 48), S(23, 48), S(20, 48), S(13, 43)
- };
-
- // Isolated pawn penalty by file
- const Score IsolatedPawnPenalty[8] = {
- S(25, 30), S(36, 35), S(40, 35), S(40, 35),
- S(40, 35), S(40, 35), S(36, 35), S(25, 30)
- };
-
- // Backward pawn penalty by file
- const Score BackwardPawnPenalty[8] = {
- S(20, 28), S(29, 31), S(33, 31), S(33, 31),
- S(33, 31), S(33, 31), S(29, 31), S(20, 28)
- };
+ // Doubled pawn penalty by opposed flag and file
+ const Score DoubledPawnPenalty[2][8] = {
+ { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
+ S(23, 48), S(23, 48), S(20, 48), S(13, 43) },
+ { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
+ S(23, 48), S(23, 48), S(20, 48), S(13, 43) }};
+
+ // Isolated pawn penalty by opposed flag and file
+ const Score IsolatedPawnPenalty[2][8] = {
+ { S(37, 45), S(54, 52), S(60, 52), S(60, 52),
+ S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
+ { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
+ S(40, 35), S(40, 35), S(36, 35), S(25, 30) }};
+
+ // Backward pawn penalty by opposed flag and file
+ const Score BackwardPawnPenalty[2][8] = {
+ { S(30, 42), S(43, 46), S(49, 46), S(49, 46),
+ S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
+ { S(20, 28), S(29, 31), S(33, 31), S(33, 31),
+ S(33, 31), S(33, 31), S(29, 31), S(20, 28) }};
// Pawn chain membership bonus by file
const Score ChainBonus[8] = {
@@ -70,175 +62,113 @@ namespace {
S(34,68), S(83,166), S(0, 0), S( 0, 0)
};
- // Pawn storm tables for positions with opposite castling
- const int QStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- -22,-22,-22,-14,-6, 0, 0, 0,
- -6,-10,-10,-10,-6, 0, 0, 0,
- 4, 12, 16, 12, 4, 0, 0, 0,
- 16, 23, 23, 16, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ const Score PawnStructureWeight = S(233, 201);
- const int KStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0,-10,-19,-28,-33,-33,
- 0, 0, 0,-10,-15,-19,-24,-24,
- 0, 0, 0, 0, 1, 1, 1, 1,
- 0, 0, 0, 0, 1, 10, 19, 19,
- 0, 0, 0, 0, 1, 19, 31, 27,
- 0, 0, 0, 0, 0, 22, 31, 22,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank]
+ const Value ShelterWeakness[2][8] =
+ { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) },
+ { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } };
- // Pawn storm open file bonuses by file
- const int16_t QStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 };
- const int16_t KStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 };
+ // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank]
+ const Value StormDanger[2][8] =
+ { { V(26), V(0), V(128), V(51), V(26) },
+ { V(13), V(0), V( 64), V(25), V(13) } };
- // Pawn storm lever bonuses by file
- const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 };
+ // Max bonus for king safety. Corresponds to start position with all the pawns
+ // in front of the king and no enemy pawn on the horizont.
+ const Value MaxSafetyBonus = V(263);
#undef S
+ #undef V
}
-////
-//// Functions
-////
-
-/// PawnInfoTable c'tor and d'tor instantiated one each thread
-
-PawnInfoTable::PawnInfoTable(unsigned numOfEntries) : size(numOfEntries) {
+/// PawnTable::probe() takes a position object as input, computes a PawnEntry
+/// object, and returns a pointer to it. The result is also stored in a hash
+/// table, so we don't have to recompute everything when the same pawn structure
+/// occurs again.
- entries = new PawnInfo[size];
- if (!entries)
- {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- Application::exit_with_failure();
- }
-}
+PawnEntry* PawnTable::probe(const Position& pos) {
+ Key key = pos.pawn_key();
+ PawnEntry* e = entries[key];
-PawnInfoTable::~PawnInfoTable() {
+ // If e->key matches the position's pawn hash key, it means that we
+ // have analysed this pawn structure before, and we can simply return
+ // the information we found the last time instead of recomputing it.
+ if (e->key == key)
+ return e;
- delete [] entries;
-}
+ e->key = key;
+ e->passedPawns[WHITE] = e->passedPawns[BLACK] = 0;
+ e->kingSquares[WHITE] = e->kingSquares[BLACK] = SQ_NONE;
+ e->halfOpenFiles[WHITE] = e->halfOpenFiles[BLACK] = 0xFF;
+ Bitboard wPawns = pos.pieces(PAWN, WHITE);
+ Bitboard bPawns = pos.pieces(PAWN, BLACK);
+ e->pawnAttacks[WHITE] = ((wPawns & ~FileHBB) << 9) | ((wPawns & ~FileABB) << 7);
+ e->pawnAttacks[BLACK] = ((bPawns & ~FileHBB) >> 7) | ((bPawns & ~FileABB) >> 9);
-/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that
-/// kingSquares[] is initialized to SQ_NONE instead.
+ e->value = evaluate_pawns(pos, wPawns, bPawns, e)
+ - evaluate_pawns(pos, bPawns, wPawns, e);
-void PawnInfo::clear() {
+ e->value = apply_weight(e->value, PawnStructureWeight);
- memset(this, 0, sizeof(PawnInfo));
- kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE;
+ return e;
}
-/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
-/// a PawnInfo object, and returns a pointer to it. The result is also stored
-/// in a hash table, so we don't have to recompute everything when the same
-/// pawn structure occurs again.
-
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
-
- assert(pos.is_ok());
-
- Key key = pos.get_pawn_key();
- unsigned index = unsigned(key & (size - 1));
- PawnInfo* pi = entries + index;
-
- // If pi->key matches the position's pawn hash key, it means that we
- // have analysed this pawn structure before, and we can simply return
- // the information we found the last time instead of recomputing it.
- if (pi->key == key)
- return pi;
-
- // Clear the PawnInfo object, and set the key
- pi->clear();
- pi->key = key;
-
- // Calculate pawn attacks
- Bitboard whitePawns = pos.pieces(PAWN, WHITE);
- Bitboard blackPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((whitePawns << 9) & ~FileABB) | ((whitePawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((blackPawns >> 7) & ~FileABB) | ((blackPawns >> 9) & ~FileHBB);
-
- // Evaluate pawns for both colors
- pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi)
- - evaluate_pawns(pos, blackPawns, whitePawns, pi);
- return pi;
-}
+/// PawnTable::evaluate_pawns() evaluates each pawn of the given color
+template
+Score PawnTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
+ Bitboard theirPawns, PawnEntry* e) {
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
-template
-Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) const {
Bitboard b;
Square s;
File f;
Rank r;
- int bonus;
bool passed, isolated, doubled, opposed, chain, backward, candidate;
Score value = SCORE_ZERO;
- const Square* ptr = pos.piece_list_begin(Us, PAWN);
-
- // Initialize pawn storm scores by giving bonuses for open files
- for (f = FILE_A; f <= FILE_H; f++)
- if (!(ourPawns & file_bb(f)))
- {
- pi->ksStormValue[Us] += KStormOpenFileBonus[f];
- pi->qsStormValue[Us] += QStormOpenFileBonus[f];
- pi->halfOpenFiles[Us] |= (1 << f);
- }
+ const Square* pl = pos.piece_list(Us, PAWN);
// Loop through all pawns of the current color and score each pawn
- while ((s = *ptr++) != SQ_NONE)
+ while ((s = *pl++) != SQ_NONE)
{
- f = square_file(s);
- r = square_rank(s);
+ assert(pos.piece_on(s) == make_piece(Us, PAWN));
- assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
+ f = file_of(s);
+ r = rank_of(s);
- // Calculate kingside and queenside pawn storm scores for both colors to be
- // used when evaluating middle game positions with opposite side castling.
- bonus = (f >= FILE_F ? evaluate_pawn_storm(s, r, f, theirPawns) : 0);
- pi->ksStormValue[Us] += KStormTable[relative_square(Us, s)] + bonus;
+ // This file cannot be half open
+ e->halfOpenFiles[Us] &= ~(1 << f);
- bonus = (f <= FILE_C ? evaluate_pawn_storm(s, r, f, theirPawns) : 0);
- pi->qsStormValue[Us] += QStormTable[relative_square(Us, s)] + bonus;
-
- // Our rank plus previous one. Used for chain detection.
+ // Our rank plus previous one. Used for chain detection
b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
- // Passed, isolated, doubled or member of a pawn
- // chain (but not the backward one) ?
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- doubled = ourPawns & squares_behind(Us, s);
+ // Flag the pawn as passed, isolated, doubled or member of a pawn
+ // chain (but not the backward one).
+ chain = ourPawns & adjacent_files_bb(f) & b;
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ doubled = ourPawns & squares_in_front_of(Us, s);
opposed = theirPawns & squares_in_front_of(Us, s);
- isolated = !(ourPawns & neighboring_files_bb(f));
- chain = ourPawns & neighboring_files_bb(f) & b;
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn
- //
backward = false;
- // If the pawn is passed, isolated, or member of a pawn chain
- // it cannot be backward. If can capture an enemy pawn or if
- // there are friendly pawns behind on neighboring files it cannot
- // be backward either.
+ // If the pawn is passed, isolated, or member of a pawn chain it cannot
+ // be backward. If there are friendly pawns behind on adjacent files
+ // or if can capture an enemy pawn it cannot be backward either.
if ( !(passed | isolated | chain)
- && !(ourPawns & attack_span_mask(opposite_color(Us), s))
+ && !(ourPawns & attack_span_mask(Them, s))
&& !(pos.attacks_from(s, Us) & theirPawns))
{
// We now know that there are no friendly pawns beside or behind this
- // pawn on neighboring files. We now check whether the pawn is
- // backward by looking in the forward direction on the neighboring
+ // pawn on adjacent files. We now check whether the pawn is
+ // backward by looking in the forward direction on the adjacent
// files, and seeing whether we meet a friendly or an enemy pawn first.
b = pos.attacks_from(s, Us);
@@ -247,45 +177,37 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
while (!(b & (ourPawns | theirPawns)))
Us == WHITE ? b <<= 8 : b >>= 8;
- // The friendly pawn needs to be at least two ranks closer than the enemy
- // pawn in order to help the potentially backward pawn advance.
+ // The friendly pawn needs to be at least two ranks closer than the
+ // enemy pawn in order to help the potentially backward pawn advance.
backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
}
- assert(passed | opposed | (attack_span_mask(Us, s) & theirPawns));
+ assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns));
- // Test for candidate passed pawn
- candidate = !(opposed | passed)
- && (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
- && count_1s_max_15(b) >= count_1s_max_15(attack_span_mask(Us, s) & theirPawns);
+ // A not passed pawn is a candidate to become passed if it is free to
+ // advance and if the number of friendly pawns beside or behind this
+ // pawn on adjacent files is higher or equal than the number of
+ // enemy pawns in the forward direction on the adjacent files.
+ candidate = !(opposed | passed | backward | isolated)
+ && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
+ && popcount(b) >= popcount(attack_span_mask(Us, s) & theirPawns);
- // In order to prevent doubled passed pawns from receiving a too big
- // bonus, only the frontmost passed pawn on each file is considered as
- // a true passed pawn.
- if (passed && (ourPawns & squares_in_front_of(Us, s)))
- passed = false;
-
- // Mark the pawn as passed. Pawn will be properly scored in evaluation
- // because we need full attack info to evaluate passed pawns.
- if (passed)
- set_bit(&(pi->passedPawns), s);
+ // Passed pawns will be properly scored in evaluation because we need
+ // full attack info to evaluate passed pawns. Only the frontmost passed
+ // pawn on each file is considered a true passed pawn.
+ if (passed && !doubled)
+ e->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
- {
- value -= IsolatedPawnPenalty[f];
- if (!opposed)
- value -= IsolatedPawnPenalty[f] / 2;
- }
+ value -= IsolatedPawnPenalty[opposed][f];
+
if (doubled)
- value -= DoubledPawnPenalty[f];
+ value -= DoubledPawnPenalty[opposed][f];
if (backward)
- {
- value -= BackwardPawnPenalty[f];
- if (!opposed)
- value -= BackwardPawnPenalty[f] / 2;
- }
+ value -= BackwardPawnPenalty[opposed][f];
+
if (chain)
value += ChainBonus[f];
@@ -297,53 +219,63 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
}
-/// PawnInfoTable::evaluate_pawn_storm() evaluates each pawn which seems
-/// to have good chances of creating an open file by exchanging itself
-/// against an enemy pawn on an adjacent file.
+/// PawnEntry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two adjacent files.
-template
-int PawnInfoTable::evaluate_pawn_storm(Square s, Rank r, File f, Bitboard theirPawns) const {
-
- const Bitboard StormFilesBB = (Side == KingSide ? FileFBB | FileGBB | FileHBB
- : FileABB | FileBBB | FileCBB);
- const int K = (Side == KingSide ? 2 : 4);
- const File RookFile = (Side == KingSide ? FILE_H : FILE_A);
+template
+Value PawnEntry::shelter_storm(const Position& pos, Square ksq) {
- Bitboard b = attack_span_mask(Us, s) & theirPawns & StormFilesBB;
- int bonus = 0;
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
- while (b)
- {
- // Give a bonus according to the distance of the nearest enemy pawn
- Square s2 = pop_1st_bit(&b);
- Rank r2 = square_rank(s2);
- int v = StormLeverBonus[f] - K * rank_distance(r, r2);
+ Value safety = MaxSafetyBonus;
+ Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Rank rkUs, rkThem;
+ File kf = file_of(ksq);
- // If enemy pawn has no pawn beside itself is particularly vulnerable.
- // Big bonus, especially against a weakness on the rook file
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- v *= (square_file(s2) == RookFile ? 4 : 2);
+ kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf;
- bonus += v;
+ for (int f = kf - 1; f <= kf + 1; f++)
+ {
+ // Shelter penalty is higher for the pawn in front of the king
+ b = ourPawns & FileBB[f];
+ rkUs = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
+ safety -= ShelterWeakness[f != kf][rkUs];
+
+ // Storm danger is smaller if enemy pawn is blocked
+ b = theirPawns & FileBB[f];
+ rkThem = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
+ safety -= StormDanger[rkThem == rkUs + 1][rkThem];
}
- return bonus;
+
+ return safety;
}
-/// PawnInfo::updateShelter calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total get_king_shelter() calls.
-int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {
+/// PawnEntry::update_safety() calculates and caches a bonus for king safety. It is
+/// called only when king square changes, about 20% of total king_safety() calls.
- Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
- unsigned shelter = 0;
- unsigned r = ksq & (7 << 3);
+template
+Score PawnEntry::update_safety(const Position& pos, Square ksq) {
- for (int i = 1, k = (c ? -8 : 8); i < 4; i++)
- {
- r += k;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
- }
- kingSquares[c] = ksq;
- kingShelters[c] = shelter;
- return shelter;
+ kingSquares[Us] = ksq;
+
+ if (relative_rank(Us, ksq) > RANK_4)
+ return kingSafety[Us] = SCORE_ZERO;
+
+ Value bonus = shelter_storm(pos, ksq);
+
+ // If we can castle use the bonus after the castle if is bigger
+ if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1)));
+
+ return kingSafety[Us] = make_score(bonus, 0);
}
+
+// Explicit template instantiation
+template Score PawnEntry::update_safety(const Position& pos, Square ksq);
+template Score PawnEntry::update_safety(const Position& pos, Square ksq);