/*
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 {
// Backward pawn penalty by opposed flag and file
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(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) } };
- // Connected pawn bonus by opposed, phalanx flags and rank
- Score Connected[2][2][RANK_NB];
+ // 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] = {
// 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)
+ };
+
+ 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(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) } };
+ { 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) } };
// Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
const Value StormDanger[][4][RANK_NB] = {
- { { 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) } } };
+ { { 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) } } };
// 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(257);
+ const Value MaxSafetyBonus = V(258);
#undef S
#undef V
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b, p, doubled, connected;
+ Bitboard b, neighbours, doubled, supported, phalanx;
Square s;
- bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
+ bool passed, isolated, opposed, backward, lever, connected;
Score score = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
// 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));
+ // 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, or connected it cannot be
+ // 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 can capture an enemy pawn it cannot be backward either.
- if ( (passed | isolated | connected)
- || (ourPawns & pawn_attack_span(Them, s))
- || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+ // it cannot be backward either.
+ if ( (passed | isolated | lever | connected)
+ || (ourPawns & pawn_attack_span(Them, s)))
backward = false;
else
{
- // We now know that there are no friendly pawns beside or behind this
+ // 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.
// Score this pawn
if (isolated)
score -= Isolated[opposed][f];
-
- if (unsupported && !isolated)
+ else if (backward)
+ score -= Backward[opposed][f];
+ else if (!supported)
score -= UnsupportedPawnPenalty;
+ 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 (backward)
- score -= Backward[opposed][f];
-
- if (connected)
- score += Connected[opposed][phalanx][relative_rank(Us, s)];
-
+
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;
}
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()
{
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);
- }
+ 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);
+ }
}
-/// 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;
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
- minKingPawnDistance[Us] = 0;
+ int minKingPawnDistance = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
+ while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return make_score(0, -16 * minKingPawnDistance[Us]);
+ return make_score(0, -16 * minKingPawnDistance);
Value bonus = shelter_storm<Us>(pos, ksq);
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
- return make_score(bonus, -16 * minKingPawnDistance[Us]);
+ return make_score(bonus, -16 * minKingPawnDistance);
}
// Explicit template instantiation
projects / stockfish / blobdiff