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) 2015-2017 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
#include <cassert>
#include "bitboard.h"
-#include "bitcount.h"
#include "pawns.h"
#include "position.h"
#include "thread.h"
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // 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 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 and file
- const Score Backward[2][FILE_NB] = {
- { S(50, 52), S(63, 56), S(69, 56), S(69, 56),
- S(69, 56), S(69, 56), S(63, 56), S(50, 52) },
- { S(40, 38), S(49, 41), S(53, 41), S(53, 41),
- S(53, 41), S(53, 41), S(49, 41), S(40, 38) } };
+ // Isolated pawn penalty by opposed flag
+ const Score Isolated[] = { S(45, 40), S(30, 27) };
+
+ // Backward pawn penalty by opposed flag
+ const Score Backward[] = { S(56, 33), S(41, 19) };
+
+ // Unsupported pawn penalty for pawns which are neither isolated or backward
+ const Score Unsupported = S(17, 8);
// Connected pawn bonus by opposed, phalanx, twice supported and rank
Score Connected[2][2][2][RANK_NB];
- // 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) };
+ // Doubled pawn penalty
+ const Score Doubled = S(18, 38);
- // Unsupported pawn penalty
- const Score UnsupportedPawnPenalty = S(20, 10);
-
- // Center bind bonus: Two pawns controlling the same central square
- const Bitboard CenterBindMask[COLOR_NB] = {
- (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB),
- (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB)
+ // Lever bonus by rank
+ const Score Lever[RANK_NB] = {
+ S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
+ S(17, 16), S(33, 32), S(0, 0), S(0, 0)
};
- const Score CenterBind = S(16, 0);
-
- // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
+ // Weakness of our pawn shelter in front of the king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
const Value ShelterWeakness[][RANK_NB] = {
- { V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) },
- { V(117), V( 1), V(27), V(71), V(94), V(104), V(118) },
- { V(104), V( 4), V(51), V(76), V(82), V(102), V( 97) },
- { V( 80), V(12), V(43), V(65), V(88), V( 91), V(115) } };
+ { V(100), V(20), V(10), V(46), V(82), V( 86), V( 98) },
+ { V(116), V( 4), V(28), V(87), V(94), V(108), V(104) },
+ { V(109), V( 1), V(59), V(87), V(62), V( 91), V(116) },
+ { V( 75), V(12), V(43), V(59), V(90), V( 84), V(112) }
+ };
- // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
+ // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has no pawn
+ // on the given file, or their pawn is behind our king.
const Value StormDanger[][4][RANK_NB] = {
- { { V( 0), V( 65), V( 126), V(36), V(30) },
- { V( 0), V( 55), V( 135), V(36), V(23) },
- { V( 0), V( 47), V( 116), V(45), V(26) },
- { V( 0), V( 62), V( 127), V(57), V(34) } },
- { { V(21), V( 45), V( 93), V(50), V(19) },
- { V(23), V( 24), V( 105), V(41), V(13) },
- { V(23), V( 36), V( 101), V(38), V(20) },
- { V(30), V( 19), V( 110), V(41), V(27) } },
- { { V( 0), V( 0), V( 81), V(14), V( 4) },
- { V( 0), V( 0), V( 169), V(30), V( 3) },
- { V( 0), V( 0), V( 168), V(24), V( 5) },
- { V( 0), V( 0), V( 162), V(26), V(10) } },
- { { V( 0), V(-283), V(-298), V(57), V(29) },
- { V( 0), V( 63), V( 137), V(42), V(18) },
- { V( 0), V( 67), V( 145), V(49), V(33) },
- { V( 0), V( 62), V( 126), V(53), V(21) } } };
+ { { V( 0), V(-290), V(-274), V(57), V(41) }, //BlockedByKing
+ { V( 0), V( 60), V( 144), V(39), V(13) },
+ { V( 0), V( 65), V( 141), V(41), V(34) },
+ { V( 0), V( 53), V( 127), V(56), V(14) } },
+ { { V( 4), V( 73), V( 132), V(46), V(31) }, //Unopposed
+ { V( 1), V( 64), V( 143), V(26), V(13) },
+ { V( 1), V( 47), V( 110), V(44), V(24) },
+ { V( 0), V( 72), V( 127), V(50), V(31) } },
+ { { V( 0), V( 0), V( 79), V(23), V( 1) }, //BlockedByPawn
+ { V( 0), V( 0), V( 148), V(27), V( 2) },
+ { V( 0), V( 0), V( 161), V(16), V( 1) },
+ { V( 0), V( 0), V( 171), V(22), V(15) } },
+ { { V(22), V( 45), V( 104), V(62), V( 6) }, //Unblocked
+ { V(31), V( 30), V( 99), V(39), V(19) },
+ { V(23), V( 29), V( 96), V(41), V(15) },
+ { V(21), V( 23), V( 116), V(41), V(15) } }
+ };
// 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.
template<Color Us>
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);
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
+ const Square Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
+ const Square Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
- Bitboard b, neighbours, doubled, supported, phalanx;
+ Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard lever, leverPush, connected;
Square s;
- bool passed, isolated, opposed, backward, lever, connected;
+ bool opposed, backward;
Score score = SCORE_ZERO;
- const Square* pl = pos.list<PAWN>(Us);
- const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
+ const Square* pl = pos.squares<PAWN>(Us);
Bitboard ourPawns = pos.pieces(Us , PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = 0;
- e->kingSquares[Us] = SQ_NONE;
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
e->semiopenFiles[Us] = 0xFF;
- e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
- e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(ourPawns & DarkSquares);
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = shift<Right>(ourPawns) | shift<Left>(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
// Loop through all pawns of the current color and score each pawn
File f = file_of(s);
- // This file cannot be semi-open
- e->semiopenFiles[Us] &= ~(1 << f);
+ 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
- // it cannot be backward either.
- if ( (passed | isolated | lever | connected)
- || (ourPawns & pawn_attack_span(Them, s)))
+ opposed = theirPawns & forward_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_mask(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);
+ supported = neighbours & rank_bb(s - Up);
+ connected = supported | phalanx;
+
+ // A pawn is backward when it is behind all pawns of the same color on the
+ // adjacent files and cannot be safely advanced.
+ if (!neighbours || lever || 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<Up>(b)) & theirPawns;
- }
+ // Find the backmost rank with neighbours or stoppers
+ b = rank_bb(backmost_sq(Us, neighbours | stoppers));
- assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
+ // The pawn is backward when it cannot safely progress to that rank:
+ // either there is a stopper in the way on this rank, or there is a
+ // stopper on adjacent file which controls the way to that rank.
+ backward = (b | shift<Up>(b & adjacent_files_bb(f))) & stoppers;
+
+ assert(!backward || !(pawn_attack_span(Them, s + Up) & neighbours));
+ }
// 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)
+ // 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)
+ && !(ourPawns & forward_bb(Us, s))
+ && popcount(supported) >= popcount(lever)
+ && popcount(phalanx) >= popcount(leverPush))
e->passedPawns[Us] |= s;
+ else if ( stoppers == SquareBB[s + Up]
+ && relative_rank(Us, s) >= RANK_5)
+ {
+ b = shift<Up>(supported) & ~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 (!neighbours)
+ score -= Isolated[opposed];
else if (backward)
- score -= Backward[opposed][f];
+ score -= Backward[opposed];
else if (!supported)
- score -= UnsupportedPawnPenalty;
+ score -= Unsupported;
if (connected)
score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
- if (doubled)
- score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
+ if (doubled && !supported)
+ score -= Doubled;
if (lever)
score += Lever[relative_rank(Us, s)];
}
- b = e->semiopenFiles[Us] ^ 0xFF;
- e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
-
- // Center binds: Two pawns controlling the same central square
- b = shift_bb<Right>(ourPawns) & shift_bb<Left>(ourPawns) & CenterBindMask[Us];
- score += popcount<Max15>(b) * CenterBind;
-
return score;
}
/// 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 };
+void init() {
+
+ static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 };
for (int opposed = 0; opposed <= 1; ++opposed)
for (int phalanx = 0; phalanx <= 1; ++phalanx)
{
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);
+ Connected[opposed][phalanx][apex][r] = make_score(v, v * (r-2) / 4);
}
}
e->key = key;
e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+ e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+ e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
return e;
}
/// Entry::shelter_storm() calculates shelter and storm penalties for the file
-/// the king is on, as well as the two adjacent files.
+/// the king is on, as well as the two closest files.
template<Color Us>
Value Entry::shelter_storm(const Position& pos, Square ksq) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
- enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
+ enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked };
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
Bitboard ourPawns = b & pos.pieces(Us);
b = theirPawns & file_bb(f);
Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
- safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+ int d = std::min(f, FILE_H - f);
+ safety -= ShelterWeakness[d][rkUs]
+ StormDanger
[f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
- rkUs == RANK_1 ? NoFriendlyPawn :
+ rkUs == RANK_1 ? Unopposed :
rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
- [std::min(f, FILE_H - f)][rkThem];
+ [d][rkThem];
}
return safety;
if (pawns)
while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
- if (relative_rank(Us, ksq) > RANK_4)
- return make_score(0, -16 * minKingPawnDistance);
-
Value bonus = shelter_storm<Us>(pos, ksq);
// If we can castle use the bonus after the castling if it is bigger
projects / stockfish / blobdiff