X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;ds=inline;f=src%2Fpawns.cpp;h=e2b26344986ad51d129aafbf9fba91ba8d2857fc;hb=ca6ce6398b1bd21ff2ac29b2dc27d7c25abbb509;hp=52f626f16b5c302c071d64d03f418c817230a0e8;hpb=1de97337c2d53bdff0f1c3f362d232028ef736a5;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
index 52f626f1..e2b26344 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -2,7 +2,7 @@
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, 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
@@ -18,11 +18,9 @@
along with this program. If not, see .
*/
-#include
#include
#include "bitboard.h"
-#include "bitcount.h"
#include "pawns.h"
#include "position.h"
#include "thread.h"
@@ -32,65 +30,32 @@ namespace {
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // Isolated pawn penalty by opposed flag and file
- 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) } };
-
- // Backward pawn penalty by opposed flag
- const Score Backward[2] = { S(67, 42), S(49, 24) };
-
- // Unsupported pawn penalty for pawns which are neither isolated or backward,
- // by number of pawns it supports [less than 2 / exactly 2].
- const Score Unsupported[2] = { S(20, 10), S(25, 15) };
-
- // Connected pawn bonus by opposed, phalanx, twice supported and rank
- Score Connected[2][2][2][RANK_NB];
-
- // 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) };
-
- // Lever 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) };
-
- // Center bind bonus, when two pawns controls the same central square
- const Score CenterBind = S(16, 0);
-
- // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
- const Value ShelterWeakness[][RANK_NB] = {
- { V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
- { V(120), V( 0), V(28), V(76), V(88), V(103), V(104) },
- { V(101), V( 7), V(54), V(78), V(77), V( 92), V(101) },
- { V( 80), V(11), V(44), V(68), V(87), V( 90), V(119) } };
-
- // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
- const Value StormDanger[][4][RANK_NB] = {
- { { V( 0), V( 67), V( 134), V(38), V(32) },
- { V( 0), V( 57), V( 139), V(37), V(22) },
- { V( 0), V( 43), V( 115), V(43), V(27) },
- { V( 0), V( 68), V( 124), V(57), V(32) } },
- { { V(20), V( 43), V( 100), V(56), V(20) },
- { V(23), V( 20), V( 98), V(40), V(15) },
- { V(23), V( 39), V( 103), V(36), V(18) },
- { V(28), V( 19), V( 108), V(42), V(26) } },
- { { V( 0), V( 0), V( 75), V(14), V( 2) },
- { V( 0), V( 0), V( 150), V(30), V( 4) },
- { V( 0), V( 0), V( 160), V(22), V( 5) },
- { V( 0), V( 0), V( 166), V(24), V(13) } },
- { { V( 0), V(-283), V(-281), V(57), V(31) },
- { V( 0), V( 58), V( 141), V(39), V(18) },
- { V( 0), V( 65), V( 142), V(48), V(32) },
- { V( 0), V( 60), V( 126), V(51), V(19) } } };
-
- // 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(258);
+ // Pawn penalties
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+
+ // Connected pawn bonus
+ constexpr int Connected[RANK_NB] = { 0, 13, 17, 24, 59, 96, 171 };
+
+ // Strength of pawn shelter for our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
+ constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = {
+ { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) },
+ { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) },
+ { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) },
+ { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) }
+ };
+
+ // Danger of enemy pawns moving toward our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
+ // is behind our king.
+ constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
+ { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) },
+ { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) },
+ { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) },
+ { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) }
+ };
#undef S
#undef V
@@ -98,31 +63,22 @@ namespace {
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);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- const Bitboard CenterBindMask =
- Us == WHITE ? (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB)
- : (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB);
-
- Bitboard b, neighbours, doubled, supported, phalanx;
+ Bitboard b, neighbours, stoppers, doubled, support, phalanx;
+ Bitboard lever, leverPush;
Square s;
- bool passed, isolated, opposed, backward, lever, connected;
+ bool opposed, backward;
Score score = SCORE_ZERO;
const Square* pl = pos.squares(Us);
- const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
- Bitboard ourPawns = pos.pieces(Us , PAWN);
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[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];
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns);
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
@@ -130,77 +86,59 @@ namespace {
assert(pos.piece_on(s) == make_piece(Us, PAWN));
File f = file_of(s);
+ Rank r = relative_rank(Us, s);
- e->semiopenFiles[Us] &= ~(1 << f);
e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
// Flag the pawn
- neighbours = 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];
- phalanx = neighbours & rank_bb(s);
- supported = neighbours & rank_bb(s - Up);
- connected = supported | phalanx;
- isolated = !neighbours;
-
- // Test for backward pawn.
- // If the pawn is passed, isolated, lever or connected it cannot be
- // backward. If there are friendly pawns behind on adjacent files
- // or if it is sufficiently advanced, it cannot be backward either.
- if ( (passed | isolated | lever | connected)
- || (ourPawns & pawn_attack_span(Them, s))
- || (relative_rank(Us, s) >= RANK_5))
- backward = false;
- else
- {
- // We now know 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));
+ opposed = theirPawns & forward_file_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_span(Us, s);
+ lever = theirPawns & PawnAttacks[Us][s];
+ leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ doubled = ourPawns & (s - Up);
+ neighbours = ourPawns & adjacent_files_bb(f);
+ phalanx = neighbours & rank_bb(s);
+ support = neighbours & rank_bb(s - Up);
+
+ // A pawn is backward when it is behind all pawns of the same color
+ // on the adjacent files and cannot be safely advanced.
+ backward = !(ourPawns & pawn_attack_span(Them, s + Up))
+ && (stoppers & (leverPush | (s + Up)));
// Passed pawns will be properly scored in evaluation because we need
- // full attack info to evaluate them. Only the frontmost passed
- // pawn on each file is considered a true passed pawn.
- if (passed && !doubled)
+ // full attack info to evaluate them. Include also not passed pawns
+ // which could become passed after one or two pawn pushes when are
+ // not attacked more times than defended.
+ if ( !(stoppers ^ lever ^ leverPush)
+ && (support || !more_than_one(lever))
+ && popcount(phalanx) >= popcount(leverPush))
e->passedPawns[Us] |= s;
+ else if (stoppers == square_bb(s + Up) && r >= RANK_5)
+ {
+ b = shift(support) & ~theirPawns;
+ while (b)
+ if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+ e->passedPawns[Us] |= s;
+ }
+
// Score this pawn
- if (isolated)
- score -= Isolated[opposed][f];
+ if (support | phalanx)
+ {
+ int v = (phalanx ? 3 : 2) * Connected[r];
+ v = 17 * popcount(support) + (v >> (opposed + 1));
+ score += make_score(v, v * (r - 2) / 4);
+ }
+ else if (!neighbours)
+ score -= Isolated, e->weakUnopposed[Us] += !opposed;
else if (backward)
- score -= Backward[opposed];
-
- else if (!supported)
- score -= Unsupported[more_than_one(neighbours & rank_bb(s + Up))];
+ score -= Backward, e->weakUnopposed[Us] += !opposed;
- if (connected)
- score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
-
- if (doubled)
- score -= Doubled[f] / distance(s, frontmost_sq(Us, doubled));
-
- if (lever)
- score += Lever[relative_rank(Us, s)];
+ if (doubled && !support)
+ score -= Doubled;
}
- b = e->semiopenFiles[Us] ^ 0xFF;
- e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
-
- b = shift_bb(ourPawns) & shift_bb(ourPawns) & CenterBindMask;
- score += CenterBind * popcount(b);
-
return score;
}
@@ -208,26 +146,6 @@ namespace {
namespace Pawns {
-/// Pawns::init() initializes some tables needed by evaluation. Instead of using
-/// 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.
-
-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 (int apex = 0; apex <= 1; ++apex)
- for (Rank r = RANK_2; r < RANK_8; ++r)
- {
- int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
- v += (apex ? v / 2 : 0);
- Connected[opposed][phalanx][apex][r] = make_score(3 * v / 2, v);
- }
-}
-
-
/// Pawns::probe() looks up the current position's pawns configuration in
/// the pawns hash table. It returns a pointer to the Entry if the position
/// is found. Otherwise a new Entry is computed and stored there, so we don't
@@ -242,42 +160,43 @@ Entry* probe(const Position& pos) {
return e;
e->key = key;
- e->score = evaluate(pos, e) - evaluate(pos, e);
- e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+ e->scores[WHITE] = evaluate(pos, e);
+ e->scores[BLACK] = evaluate(pos, e);
+
return e;
}
-/// Entry::shelter_storm() calculates shelter and storm penalties for the file
-/// the king is on, as well as the two adjacent files.
+/// Entry::evaluate_shelter() calculates the shelter bonus and the storm
+/// penalty for a king, looking at the king file and the two closest files.
template
-Value Entry::shelter_storm(const Position& pos, Square ksq) {
+Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
+ constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
- enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
-
- Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
+ Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = MaxSafetyBonus;
- File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (File f = center - File(1); f <= center + File(1); ++f)
+ Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
+ Value(374) : Value(5);
+
+ File center = clamp(file_of(ksq), FILE_B, FILE_G);
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+ Rank ourRank = 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;
+ b = theirPawns & file_bb(f);
+ Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
- safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
- + StormDanger
- [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
- rkUs == RANK_1 ? NoFriendlyPawn :
- rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
- [std::min(f, FILE_H - f)][rkThem];
+ int d = std::min(f, ~f);
+ safety += ShelterStrength[d][ourRank];
+ safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3)
+ : UnblockedStorm[d][theirRank];
}
return safety;
@@ -288,33 +207,31 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
/// when king square changes, which is about 20% of total king_safety() calls.
template
-Score Entry::do_king_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos) {
+ Square ksq = pos.square(Us);
kingSquares[Us] = ksq;
- castlingRights[Us] = pos.can_castle(Us);
+ castlingRights[Us] = pos.castling_rights(Us);
int minKingPawnDistance = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
-
- if (relative_rank(Us, ksq) > RANK_4)
- return make_score(0, -16 * minKingPawnDistance);
+ while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
- Value bonus = shelter_storm(pos, ksq);
+ Value bonus = evaluate_shelter(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(Us | KING_SIDE))
+ bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(MakeCastling::right))
- bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1)));
+ if (pos.can_castle(Us | QUEEN_SIDE))
+ bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_C1)));
return make_score(bonus, -16 * minKingPawnDistance);
}
// Explicit template instantiation
-template Score Entry::do_king_safety(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);
+template Score Entry::do_king_safety(const Position& pos);
} // namespace Pawns