/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 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
#include "bitcount.h"
#include "pawns.h"
#include "position.h"
+#include "thread.h"
namespace {
// Unsupported pawn penalty
const Score UnsupportedPawnPenalty = S(20, 10);
- // Weakness of our pawn shelter in front of the king indexed by [file pairs (a/h,b/g,c/f,d/e)][rank]
+ // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
const Value ShelterWeakness[][RANK_NB] = {
- { V(101), V(10), V(24), V(68), V(90), V( 95), V(102) },
- { V(105), V( 1), V(30), V(76), V(95), V(100), V(105) },
- { V( 99), V( 0), V(32), V(72), V(92), V(101), V(100) },
- { V( 94), V( 1), V(31), V(68), V(89), V( 98), V(106) } };
+ { V(100), V(13), V(24), V(64), V(89), V( 93), V(104) },
+ { V(110), V( 1), V(29), V(75), V(96), V(102), V(107) },
+ { V(102), V( 0), V(39), V(74), V(88), V(101), V( 98) },
+ { V( 88), V( 4), V(33), V(67), V(92), V( 94), V(107) } };
- // Danger of enemy pawns moving toward our king indexed by
- // [file pairs (a/h,b/g,c/f,d/e)][no friendly pawn | pawn unblocked | pawn blocked by pawn| pawn blocked by king][rank of enemy pawn]
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
const Value StormDanger[][4][RANK_NB] = {
- { { V( 0), V( 61), V( 128), V(47), V(27) },
- { V(25), V( 33), V( 95), V(39), V(21) },
- { V( 0), V( 0), V( 80), V(14), V( 8) },
- { V( 0), V(-300), V(-300), V(54), V(23) } },
- { { V( 0), V( 66), V( 131), V(49), V(27) },
- { V(24), V( 33), V( 97), V(42), V(22) },
- { V( 0), V( 0), V( 163), V(28), V(12) },
- { V( 0), V( 67), V( 128), V(46), V(24) } },
- { { V( 0), V( 62), V( 126), V(52), V(23) },
- { V(24), V( 33), V( 93), V(35), V(23) },
- { V( 0), V( 0), V( 163), V(25), V(15) },
- { V( 0), V( 64), V( 130), V(50), V(29) } },
- { { V( 0), V( 63), V( 128), V(52), V(26) },
- { V(26), V( 27), V( 96), V(37), V(22) },
- { V( 0), V( 0), V( 161), V(24), V(14) },
- { V( 0), V( 63), V( 127), V(51), V(24) } } };
+ { { V( 0), V( 63), V( 128), V(43), V(27) },
+ { V( 0), V( 62), V( 131), V(44), V(26) },
+ { V( 0), V( 59), V( 121), V(50), V(28) },
+ { V( 0), V( 62), V( 127), V(54), V(28) } },
+ { { V(24), V( 40), V( 93), V(42), V(22) },
+ { V(24), V( 28), V( 101), V(38), V(20) },
+ { V(24), V( 32), V( 95), V(36), V(23) },
+ { V(27), V( 24), V( 99), V(36), V(24) } },
+ { { V( 0), V( 0), V( 81), V(16), V( 6) },
+ { V( 0), V( 0), V( 165), V(29), V( 9) },
+ { V( 0), V( 0), V( 163), V(23), V(12) },
+ { V( 0), V( 0), V( 161), V(28), V(13) } },
+ { { V( 0), V(-296), V(-299), V(55), V(25) },
+ { V( 0), V( 67), V( 131), V(46), V(21) },
+ { V( 0), V( 65), V( 135), V(50), V(31) },
+ { V( 0), V( 62), V( 128), V(51), V(24) } } };
// 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(261);
+ const Value MaxSafetyBonus = V(257);
#undef S
#undef V
Bitboard b, p, doubled, connected;
Square s;
bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
- Score value = SCORE_ZERO;
+ Score score = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
// Score this pawn
if (isolated)
- value -= Isolated[opposed][f];
+ score -= Isolated[opposed][f];
if (unsupported && !isolated)
- value -= UnsupportedPawnPenalty;
+ score -= UnsupportedPawnPenalty;
if (doubled)
- value -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
+ score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
if (backward)
- value -= Backward[opposed][f];
+ score -= Backward[opposed][f];
if (connected)
- value += Connected[opposed][phalanx][relative_rank(Us, s)];
+ score += Connected[opposed][phalanx][relative_rank(Us, s)];
if (lever)
- value += Lever[relative_rank(Us, s)];
+ score += Lever[relative_rank(Us, s)];
}
b = e->semiopenFiles[Us] ^ 0xFF;
e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
- return value;
+ return score;
}
} // namespace
namespace Pawns {
-/// 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.
+/// 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()
{
}
-/// 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.
+/// 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
+/// have to recompute all when the same pawns configuration occurs again.
-Entry* probe(const Position& pos, Table& entries) {
+Entry* probe(const Position& pos) {
Key key = pos.pawn_key();
- Entry* e = entries[key];
+ Entry* e = pos.this_thread()->pawnsTable[key];
if (e->key == key)
return e;
e->key = key;
- e->value = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+ e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
return e;
}
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
+
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)));
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (File f = kf - File(1); f <= kf + File(1); ++f)
+ for (File f = center - File(1); f <= center + File(1); ++f)
{
b = ourPawns & file_bb(f);
Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
- + StormDanger[std::min(f, FILE_H - f)]
- [file_of(ksq) == f && relative_rank(Us, ksq) == rkThem - 1 ? 3 :
- rkUs == RANK_1 ? 0 :
- rkThem != rkUs + 1 ? 1 :
- /* pawn blocked by pawn */ 2 ]
- [rkThem];
+ + 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];
}
return safety;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
+ while (!(DistanceRingBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
return make_score(0, -16 * minKingPawnDistance[Us]);