X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=d6ea1479de80c407449863709208db76fa1b13c3;hb=46d5fff01fbeafdf822e440231845363ba979f09;hp=3aede5adfa7f111b42ddef9332e9182a5dfba8f5;hpb=a44c5cf4f77b05a0385c127b7c26cf086a73120e;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
index 3aede5ad..d6ea1479 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) 2008-2014 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
@@ -17,6 +17,7 @@
along with this program. If not, see .
*/
+#include
#include
#include "bitboard.h"
@@ -26,216 +27,274 @@
namespace {
+ #define V Value
#define S(mg, eg) make_score(mg, eg)
- // 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) }};
+ // Doubled pawn penalty by file
+ const Score Doubled[FILE_NB] = {
+ 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] = {
+ const Score Isolated[2][FILE_NB] = {
{ 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) }};
+ 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] = {
+ const Score Backward[2][FILE_NB] = {
{ 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) }};
+ S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
- // Pawn chain membership bonus by file
- const Score ChainBonus[8] = {
- S(11,-1), S(13,-1), S(13,-1), S(14,-1),
- S(14,-1), S(13,-1), S(13,-1), S(11,-1)
- };
+ // Connected pawn bonus by opposed, phalanx flags and rank
+ Score Connected[2][2][RANK_NB];
- // Candidate passed pawn bonus by rank
- const Score CandidateBonus[8] = {
- S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0)
- };
+ // Levers bonus by rank
+ const Score Lever[RANK_NB] = {
+ S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
+ S(20,20), S(40,40), S(0, 0), S(0, 0) };
- const Score PawnStructureWeight = S(233, 201);
+ // Unsupported pawn penalty
+ const Score UnsupportedPawnPenalty = S(20, 10);
- #undef S
+ // Weakness of our pawn shelter in front of the king indexed by [rank]
+ const Value ShelterWeakness[RANK_NB] =
+ { V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
+
+ // Danger of enemy pawns moving toward our king indexed by
+ // [edge files][no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
+ const Value StormDanger[][3][RANK_NB] = {
+ { { V( 0), V(64), V(128), V(51), V(26) },
+ { V(26), V(32), V( 96), V(38), V(20) },
+ { V( 0), V( 0), V(160), V(25), V(13) } },
+ { { V( 0), V(64), V(128), V(51), V(26) },
+ { V(26), V(32), V( 96), V(38), V(20) },
+ { V( 0), V( 0), V( 80), V(13), V( 7) } } };
+
+ // Max bonus for king safety. Corresponds to start position with all the pawns
+ // in front of the king and no enemy pawn on the horizon.
+ const Value MaxSafetyBonus = V(263);
- inline Score apply_weight(Score v, Score w) {
- return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
- (int(eg_value(v)) * eg_value(w)) / 0x100);
+ #undef S
+ #undef V
+
+ template
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
+ const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
+ const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
+
+ Bitboard b, p, doubled, connected;
+ Square s;
+ bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
+ Score value = SCORE_ZERO;
+ const Square* pl = pos.list(Us);
+ const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
+
+ Bitboard ourPawns = pos.pieces(Us , PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ e->passedPawns[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->semiopenFiles[Us] = 0xFF;
+ e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
+ e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK];
+
+ // Loop through all pawns of the current color and score each pawn
+ while ((s = *pl++) != SQ_NONE)
+ {
+ assert(pos.piece_on(s) == make_piece(Us, PAWN));
+
+ File f = file_of(s);
+
+ // This file cannot be semi-open
+ e->semiopenFiles[Us] &= ~(1 << f);
+
+ // Previous rank
+ p = rank_bb(s - pawn_push(Us));
+
+ // Flag the pawn as passed, isolated, doubled,
+ // unsupported or connected (but not the backward one).
+ connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p);
+ phalanx = connected & rank_bb(s);
+ unsupported = !(ourPawns & adjacent_files_bb(f) & p);
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ doubled = ourPawns & forward_bb(Us, s);
+ opposed = theirPawns & forward_bb(Us, s);
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
+ lever = theirPawns & pawnAttacksBB[s];
+
+ // Test for backward pawn.
+ // If the pawn is passed, isolated, or connected it cannot be
+ // backward. If there are friendly pawns behind on adjacent files
+ // or if it can capture an enemy pawn it cannot be backward either.
+ if ( (passed | isolated | connected)
+ || (ourPawns & pawn_attack_span(Them, s))
+ || (pos.attacks_from(s, Us) & theirPawns))
+ backward = false;
+ else
+ {
+ // We now know that there are no friendly pawns beside or behind this
+ // pawn on adjacent files. We now check whether the pawn is
+ // backward by looking in the forward direction on the adjacent
+ // files, and picking the closest pawn there.
+ b = pawn_attack_span(Us, s) & (ourPawns | theirPawns);
+ b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b));
+
+ // If we have an enemy pawn in the same or next rank, the pawn is
+ // backward because it cannot advance without being captured.
+ backward = (b | shift_bb(b)) & theirPawns;
+ }
+
+ assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
+
+ // 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 -= Isolated[opposed][f];
+
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
+ if (doubled)
+ value -= Doubled[f] / distance(s, frontmost_sq(Us, doubled));
+
+ if (backward)
+ value -= Backward[opposed][f];
+
+ if (connected)
+ value += Connected[opposed][phalanx][relative_rank(Us, s)];
+
+ if (lever)
+ value += Lever[relative_rank(Us, s)];
+ }
+
+ b = e->semiopenFiles[Us] ^ 0xFF;
+ e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
+
+ return value;
}
-}
+} // namespace
-/// 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 an hash table, so we don't have to recompute everything when the same
-/// pawn structure occurs again.
+namespace Pawns {
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
+/// init() initializes some tables used by evaluation. Instead of hard-coded
+/// tables, when makes sense, we prefer to calculate them with a formula to
+/// reduce independent parameters and to allow easier tuning and better insight.
- Key key = pos.get_pawn_key();
- PawnInfo* pi = probe(key);
+void init()
+{
+ static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
+ Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
+ }
+}
- // 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;
- // Initialize PawnInfo entry
- pi->key = key;
- pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
+/// probe() takes a position as input, computes a Entry 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.
- // Calculate pawn attacks
- Bitboard wPawns = pos.pieces(PAWN, WHITE);
- Bitboard bPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB);
+Entry* probe(const Position& pos, Table& entries) {
- // Evaluate pawns for both colors and weight the result
- pi->value = evaluate_pawns(pos, wPawns, bPawns, pi)
- - evaluate_pawns(pos, bPawns, wPawns, pi);
+ Key key = pos.pawn_key();
+ Entry* e = entries[key];
- pi->value = apply_weight(pi->value, PawnStructureWeight);
+ if (e->key == key)
+ return e;
- return pi;
+ e->key = key;
+ e->value = evaluate(pos, e) - evaluate(pos, e);
+ return e;
}
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+/// Entry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two adjacent files.
template
-Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) {
+Value Entry::shelter_storm(const Position& pos, Square ksq) {
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
- Bitboard b;
- Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- Score value = SCORE_ZERO;
- const Square* pl = pos.piece_list(Us, PAWN);
+ Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Value safety = MaxSafetyBonus;
+ File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- // Loop through all pawns of the current color and score each pawn
- while ((s = *pl++) != SQ_NONE)
+ for (File f = kf - File(1); f <= kf + File(1); ++f)
{
- assert(pos.piece_on(s) == make_piece(Us, PAWN));
-
- f = file_of(s);
- r = rank_of(s);
-
- // This file cannot be half open
- pi->halfOpenFiles[Us] &= ~(1 << f);
-
- // Our rank plus previous one. Used for chain detection
- b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
-
- // Flag the pawn as passed, isolated, doubled or member of a pawn
- // chain (but not the backward one).
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- 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;
-
- // Test for backward pawn
- backward = false;
-
- // If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on neighboring files
- // or if can capture an enemy pawn it cannot be backward either.
- if ( !(passed | isolated | chain)
- && !(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
- // files, and seeing whether we meet a friendly or an enemy pawn first.
- b = pos.attacks_from(s, Us);
-
- // Note that we are sure to find something because pawn is not passed
- // nor isolated, so loop is potentially infinite, but it isn't.
- 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.
- backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
- }
-
- assert(opposed | passed | (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 neighboring files is higher or equal than the number of
- // enemy pawns in the forward direction on the neighboring files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
- && count_1s(b) >= count_1s(attack_span_mask(Us, s) & theirPawns);
-
- // 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)
- set_bit(&(pi->passedPawns[Us]), s);
-
- // Score this pawn
- if (isolated)
- value -= IsolatedPawnPenalty[opposed][f];
-
- if (doubled)
- value -= DoubledPawnPenalty[opposed][f];
-
- if (backward)
- value -= BackwardPawnPenalty[opposed][f];
-
- if (chain)
- value += ChainBonus[f];
-
- if (candidate)
- value += CandidateBonus[relative_rank(Us, s)];
+ b = ourPawns & file_bb(f);
+ Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+
+ b = theirPawns & file_bb(f);
+ Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+
+ if ( (Edges & make_square(f, rkThem))
+ && file_of(ksq) == f
+ && relative_rank(Us, ksq) == rkThem - 1)
+ safety += 200;
+ else
+ safety -= ShelterWeakness[rkUs]
+ + StormDanger[f == FILE_A || f == FILE_H]
+ [rkUs == RANK_1 ? 0 :
+ rkThem != rkUs + 1 ? 1 : 2][rkThem];
}
- return value;
+
+ return safety;
}
-/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total king_shelter() calls.
+/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
+/// when king square changes, which is about 20% of total king_safety() calls.
+
template
-Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
- const int Shift = (Us == WHITE ? 8 : -8);
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.can_castle(Us);
+ minKingPawnDistance[Us] = 0;
- Bitboard pawns;
- int r, shelter = 0;
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
- if (relative_rank(Us, ksq) <= RANK_4)
- {
- pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(file_of(ksq));
- r = ksq & (7 << 3);
- for (int i = 0; i < 3; i++)
- {
- r += Shift;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] << (6 - i);
- }
- }
- kingSquares[Us] = ksq;
- kingShelters[Us] = make_score(shelter, 0);
- return kingShelters[Us];
+ if (relative_rank(Us, ksq) > RANK_4)
+ return make_score(0, -16 * minKingPawnDistance[Us]);
+
+ Value bonus = shelter_storm(pos, ksq);
+
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(MakeCastling::right))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(MakeCastling::right))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1)));
+
+ return make_score(bonus, -16 * minKingPawnDistance[Us]);
}
// Explicit template instantiation
-template Score PawnInfo::updateShelter(const Position& pos, Square ksq);
-template Score PawnInfo::updateShelter(const Position& pos, Square ksq);
+template Score Entry::do_king_safety(const Position& pos, Square ksq);
+template Score Entry::do_king_safety(const Position& pos, Square ksq);
+
+} // namespace Pawns