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4
src/Makefile
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@ -34,9 +34,7 @@ BINDIR = $(PREFIX)/bin
PGOBENCH = ./$(EXE) bench 16 1 1 default time
### Object files
OBJS = benchmark.o bitbase.o bitboard.o endgame.o evaluate.o main.o \
material.o misc.o movegen.o movepick.o pawns.o position.o \
search.o thread.o timeman.o tt.o uci.o ucioption.o syzygy/tbprobe.o
OBJS = main.o bitboard.o
### ==========================================================================
### Section 2. High-level Configuration

175
src/benchmark.cpp
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@ -1,175 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include <fstream>
#include <iostream>
#include <istream>
#include <vector>
#include "misc.h"
#include "position.h"
#include "search.h"
#include "thread.h"
#include "tt.h"
#include "uci.h"
using namespace std;
namespace {
const char* Defaults[] = {
"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
"r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 10",
"8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - - 0 11",
"4rrk1/pp1n3p/3q2pQ/2p1pb2/2PP4/2P3N1/P2B2PP/4RRK1 b - - 7 19",
"rq3rk1/ppp2ppp/1bnpb3/3N2B1/3NP3/7P/PPPQ1PP1/2KR3R w - - 7 14",
"r1bq1r1k/1pp1n1pp/1p1p4/4p2Q/4Pp2/1BNP4/PPP2PPP/3R1RK1 w - - 2 14",
"r3r1k1/2p2ppp/p1p1bn2/8/1q2P3/2NPQN2/PPP3PP/R4RK1 b - - 2 15",
"r1bbk1nr/pp3p1p/2n5/1N4p1/2Np1B2/8/PPP2PPP/2KR1B1R w kq - 0 13",
"r1bq1rk1/ppp1nppp/4n3/3p3Q/3P4/1BP1B3/PP1N2PP/R4RK1 w - - 1 16",
"4r1k1/r1q2ppp/ppp2n2/4P3/5Rb1/1N1BQ3/PPP3PP/R5K1 w - - 1 17",
"2rqkb1r/ppp2p2/2npb1p1/1N1Nn2p/2P1PP2/8/PP2B1PP/R1BQK2R b KQ - 0 11",
"r1bq1r1k/b1p1npp1/p2p3p/1p6/3PP3/1B2NN2/PP3PPP/R2Q1RK1 w - - 1 16",
"3r1rk1/p5pp/bpp1pp2/8/q1PP1P2/b3P3/P2NQRPP/1R2B1K1 b - - 6 22",
"r1q2rk1/2p1bppp/2Pp4/p6b/Q1PNp3/4B3/PP1R1PPP/2K4R w - - 2 18",
"4k2r/1pb2ppp/1p2p3/1R1p4/3P4/2r1PN2/P4PPP/1R4K1 b - - 3 22",
"3q2k1/pb3p1p/4pbp1/2r5/PpN2N2/1P2P2P/5PP1/Q2R2K1 b - - 4 26",
"6k1/6p1/6Pp/ppp5/3pn2P/1P3K2/1PP2P2/3N4 b - - 0 1",
"3b4/5kp1/1p1p1p1p/pP1PpP1P/P1P1P3/3KN3/8/8 w - - 0 1",
"2K5/p7/7P/5pR1/8/5k2/r7/8 w - - 0 1",
"8/6pk/1p6/8/PP3p1p/5P2/4KP1q/3Q4 w - - 0 1",
"7k/3p2pp/4q3/8/4Q3/5Kp1/P6b/8 w - - 0 1",
"8/2p5/8/2kPKp1p/2p4P/2P5/3P4/8 w - - 0 1",
"8/1p3pp1/7p/5P1P/2k3P1/8/2K2P2/8 w - - 0 1",
"8/pp2r1k1/2p1p3/3pP2p/1P1P1P1P/P5KR/8/8 w - - 0 1",
"8/3p4/p1bk3p/Pp6/1Kp1PpPp/2P2P1P/2P5/5B2 b - - 0 1",
"5k2/7R/4P2p/5K2/p1r2P1p/8/8/8 b - - 0 1",
"6k1/6p1/P6p/r1N5/5p2/7P/1b3PP1/4R1K1 w - - 0 1",
"1r3k2/4q3/2Pp3b/3Bp3/2Q2p2/1p1P2P1/1P2KP2/3N4 w - - 0 1",
"6k1/4pp1p/3p2p1/P1pPb3/R7/1r2P1PP/3B1P2/6K1 w - - 0 1",
"8/3p3B/5p2/5P2/p7/PP5b/k7/6K1 w - - 0 1",
// 5-man positions
"8/8/8/8/5kp1/P7/8/1K1N4 w - - 0 1", // Kc2 - mate
"8/8/8/5N2/8/p7/8/2NK3k w - - 0 1", // Na2 - mate
"8/3k4/8/8/8/4B3/4KB2/2B5 w - - 0 1", // draw
// 6-man positions
"8/8/1P6/5pr1/8/4R3/7k/2K5 w - - 0 1", // Re5 - mate
"8/2p4P/8/kr6/6R1/8/8/1K6 w - - 0 1", // Ka2 - mate
"8/8/3P3k/8/1p6/8/1P6/1K3n2 b - - 0 1", // Nd2 - draw
// 7-man positions
"8/R7/2q5/8/6k1/8/1P5p/K6R w - - 0 124", // Draw
};
} // namespace
/// benchmark() runs a simple benchmark by letting Stockfish analyze a set
/// of positions for a given limit each. There are five parameters: the
/// transposition table size, the number of search threads that should
/// be used, the limit value spent for each position (optional, default is
/// depth 13), an optional file name where to look for positions in FEN
/// format (defaults are the positions defined above) and the type of the
/// limit value: depth (default), time in secs or number of nodes.
void benchmark(const Position& current, istream& is) {
string token;
Search::LimitsType limits;
vector<string> fens;
// Assign default values to missing arguments
string ttSize = (is >> token) ? token : "16";
string threads = (is >> token) ? token : "1";
string limit = (is >> token) ? token : "13";
string fenFile = (is >> token) ? token : "default";
string limitType = (is >> token) ? token : "depth";
Options["Hash"] = ttSize;
Options["Threads"] = threads;
TT.clear();
if (limitType == "time")
limits.movetime = 1000 * atoi(limit.c_str()); // movetime is in ms
else if (limitType == "nodes")
limits.nodes = atoi(limit.c_str());
else if (limitType == "mate")
limits.mate = atoi(limit.c_str());
else
limits.depth = atoi(limit.c_str());
if (fenFile == "default")
fens.assign(Defaults, Defaults + 37);
else if (fenFile == "current")
fens.push_back(current.fen());
else
{
string fen;
ifstream file(fenFile.c_str());
if (!file.is_open())
{
cerr << "Unable to open file " << fenFile << endl;
return;
}
while (getline(file, fen))
if (!fen.empty())
fens.push_back(fen);
file.close();
}
uint64_t nodes = 0;
Search::StateStackPtr st;
Time::point elapsed = Time::now();
for (size_t i = 0; i < fens.size(); ++i)
{
Position pos(fens[i], Options["UCI_Chess960"], Threads.main());
cerr << "\nPosition: " << i + 1 << '/' << fens.size() << endl;
if (limitType == "perft")
nodes += Search::perft<true>(pos, limits.depth * ONE_PLY);
else
{
Threads.start_thinking(pos, limits, st);
Threads.wait_for_think_finished();
nodes += Search::RootPos.nodes_searched();
}
}
elapsed = std::max(Time::now() - elapsed, Time::point(1)); // Avoid a 'divide by zero'
dbg_print(); // Just before to exit
cerr << "\n==========================="
<< "\nTotal time (ms) : " << elapsed
<< "\nNodes searched : " << nodes
<< "\nNodes/second : " << 1000 * nodes / elapsed << endl;
}

175
src/bitbase.cpp
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@ -1,175 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <cassert>
#include <vector>
#include "bitboard.h"
#include "types.h"
namespace {
// There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
// Each uint32_t stores results of 32 positions, one per bit
uint32_t KPKBitbase[MAX_INDEX / 32];
// A KPK bitbase index is an integer in [0, IndexMax] range
//
// Information is mapped in a way that minimizes the number of iterations:
//
// bit 0- 5: white king square (from SQ_A1 to SQ_H8)
// bit 6-11: black king square (from SQ_A1 to SQ_H8)
// bit 12: side to move (WHITE or BLACK)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2)
unsigned index(Color us, Square bksq, Square wksq, Square psq) {
return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
}
enum Result {
INVALID = 0,
UNKNOWN = 1,
DRAW = 2,
WIN = 4
};
inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
struct KPKPosition {
KPKPosition(unsigned idx);
operator Result() const { return result; }
Result classify(const std::vector<KPKPosition>& db)
{ return us == WHITE ? classify<WHITE>(db) : classify<BLACK>(db); }
private:
template<Color Us> Result classify(const std::vector<KPKPosition>& db);
Color us;
Square bksq, wksq, psq;
Result result;
};
} // namespace
bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) {
assert(file_of(wpsq) <= FILE_D);
unsigned idx = index(us, bksq, wksq, wpsq);
return KPKBitbase[idx / 32] & (1 << (idx & 0x1F));
}
void Bitbases::init() {
unsigned idx, repeat = 1;
std::vector<KPKPosition> db;
db.reserve(MAX_INDEX);
// Initialize db with known win / draw positions
for (idx = 0; idx < MAX_INDEX; ++idx)
db.push_back(KPKPosition(idx));
// Iterate through the positions until none of the unknown positions can be
// changed to either wins or draws (15 cycles needed).
while (repeat)
for (repeat = idx = 0; idx < MAX_INDEX; ++idx)
repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
// Map 32 results into one KPKBitbase[] entry
for (idx = 0; idx < MAX_INDEX; ++idx)
if (db[idx] == WIN)
KPKBitbase[idx / 32] |= 1 << (idx & 0x1F);
}
namespace {
KPKPosition::KPKPosition(unsigned idx) {
wksq = Square((idx >> 0) & 0x3F);
bksq = Square((idx >> 6) & 0x3F);
us = Color ((idx >> 12) & 0x01);
psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
result = UNKNOWN;
// Check if two pieces are on the same square or if a king can be captured
if ( distance(wksq, bksq) <= 1
|| wksq == psq
|| bksq == psq
|| (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq)))
result = INVALID;
else if (us == WHITE)
{
// Immediate win if a pawn can be promoted without getting captured
if ( rank_of(psq) == RANK_7
&& wksq != psq + DELTA_N
&& ( distance(bksq, psq + DELTA_N) > 1
||(StepAttacksBB[KING][wksq] & (psq + DELTA_N))))
result = WIN;
}
// Immediate draw if it is a stalemate or a king captures undefended pawn
else if ( !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq]))
|| (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq]))
result = DRAW;
}
template<Color Us>
Result KPKPosition::classify(const std::vector<KPKPosition>& db) {
// White to Move: If one move leads to a position classified as WIN, the result
// of the current position is WIN. If all moves lead to positions classified
// as DRAW, the current position is classified as DRAW, otherwise the current
// position is classified as UNKNOWN.
//
// Black to Move: If one move leads to a position classified as DRAW, the result
// of the current position is DRAW. If all moves lead to positions classified
// as WIN, the position is classified as WIN, otherwise the current position is
// classified as UNKNOWN.
const Color Them = (Us == WHITE ? BLACK : WHITE);
Result r = INVALID;
Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq];
while (b)
r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)]
: db[index(Them, pop_lsb(&b), wksq, psq)];
if (Us == WHITE && rank_of(psq) < RANK_7)
{
Square s = psq + DELTA_N;
r |= db[index(BLACK, bksq, wksq, s)]; // Single push
if (rank_of(psq) == RANK_2 && s != wksq && s != bksq)
r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push
}
if (Us == WHITE)
return result = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW;
else
return result = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
}
} // namespace

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src/endgame.cpp
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@ -1,857 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include <cassert>
#include "bitboard.h"
#include "bitcount.h"
#include "endgame.h"
#include "movegen.h"
using std::string;
namespace {
// Table used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
const int PushToEdges[SQUARE_NB] = {
100, 90, 80, 70, 70, 80, 90, 100,
90, 70, 60, 50, 50, 60, 70, 90,
80, 60, 40, 30, 30, 40, 60, 80,
70, 50, 30, 20, 20, 30, 50, 70,
70, 50, 30, 20, 20, 30, 50, 70,
80, 60, 40, 30, 30, 40, 60, 80,
90, 70, 60, 50, 50, 60, 70, 90,
100, 90, 80, 70, 70, 80, 90, 100,
};
// Table used to drive the king towards a corner square of the
// right color in KBN vs K endgames.
const int PushToCorners[SQUARE_NB] = {
200, 190, 180, 170, 160, 150, 140, 130,
190, 180, 170, 160, 150, 140, 130, 140,
180, 170, 155, 140, 140, 125, 140, 150,
170, 160, 140, 120, 110, 140, 150, 160,
160, 150, 140, 110, 120, 140, 160, 170,
150, 140, 125, 140, 140, 155, 170, 180,
140, 130, 140, 150, 160, 170, 180, 190,
130, 140, 150, 160, 170, 180, 190, 200
};
// Tables used to drive a piece towards or away from another piece
const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
#ifndef NDEBUG
bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == pawnsCnt;
}
#endif
// Map the square as if strongSide is white and strongSide's only pawn
// is on the left half of the board.
Square normalize(const Position& pos, Color strongSide, Square sq) {
assert(pos.count<PAWN>(strongSide) == 1);
if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
if (strongSide == BLACK)
sq = ~sq;
return sq;
}
// Get the material key of Position out of the given endgame key code
// like "KBPKN". The trick here is to first forge an ad-hoc FEN string
// and then let a Position object do the work for us.
Key key(const string& code, Color c) {
assert(code.length() > 0 && code.length() < 8);
assert(code[0] == 'K');
string sides[] = { code.substr(code.find('K', 1)), // Weak
code.substr(0, code.find('K', 1)) }; // Strong
std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/"
+ sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10";
return Position(fen, false, NULL).material_key();
}
template<typename M>
void delete_endgame(const typename M::value_type& p) { delete p.second; }
} // namespace
/// Endgames members definitions
Endgames::Endgames() {
add<KPK>("KPK");
add<KNNK>("KNNK");
add<KBNK>("KBNK");
add<KRKP>("KRKP");
add<KRKB>("KRKB");
add<KRKN>("KRKN");
add<KQKP>("KQKP");
add<KQKR>("KQKR");
add<KNPK>("KNPK");
add<KNPKB>("KNPKB");
add<KRPKR>("KRPKR");
add<KRPKB>("KRPKB");
add<KBPKB>("KBPKB");
add<KBPKN>("KBPKN");
add<KBPPKB>("KBPPKB");
add<KRPPKRP>("KRPPKRP");
}
Endgames::~Endgames() {
for_each(m1.begin(), m1.end(), delete_endgame<M1>);
for_each(m2.begin(), m2.end(), delete_endgame<M2>);
}
template<EndgameType E>
void Endgames::add(const string& code) {
map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
}
/// Mate with KX vs K. This function is used to evaluate positions with
/// king and plenty of material vs a lone king. It simply gives the
/// attacking side a bonus for driving the defending king towards the edge
/// of the board, and for keeping the distance between the two kings small.
template<>
Value Endgame<KXK>::operator()(const Position& pos) const {
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
assert(!pos.checkers()); // Eval is never called when in check
// Stalemate detection with lone king
if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
return VALUE_DRAW;
Square winnerKSq = pos.king_square(strongSide);
Square loserKSq = pos.king_square(weakSide);
Value result = pos.non_pawn_material(strongSide)
+ pos.count<PAWN>(strongSide) * PawnValueEg
+ PushToEdges[loserKSq]
+ PushClose[distance(winnerKSq, loserKSq)];
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
||(pos.count<BISHOP>(strongSide) > 1 && opposite_colors(pos.list<BISHOP>(strongSide)[0],
pos.list<BISHOP>(strongSide)[1])))
result += VALUE_KNOWN_WIN;
return strongSide == pos.side_to_move() ? result : -result;
}
/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
/// defending king towards a corner square of the right color.
template<>
Value Endgame<KBNK>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
Square winnerKSq = pos.king_square(strongSide);
Square loserKSq = pos.king_square(weakSide);
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
// kbnk_mate_table() tries to drive toward corners A1 or H8. If we have a
// bishop that cannot reach the above squares, we flip the kings in order
// to drive the enemy toward corners A8 or H1.
if (opposite_colors(bishopSq, SQ_A1))
{
winnerKSq = ~winnerKSq;
loserKSq = ~loserKSq;
}
Value result = VALUE_KNOWN_WIN
+ PushClose[distance(winnerKSq, loserKSq)]
+ PushToCorners[loserKSq];
return strongSide == pos.side_to_move() ? result : -result;
}
/// KP vs K. This endgame is evaluated with the help of a bitbase.
template<>
Value Endgame<KPK>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
if (!Bitbases::probe(wksq, psq, bksq, us))
return VALUE_DRAW;
Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
return strongSide == pos.side_to_move() ? result : -result;
}
/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
/// a bitbase. The function below returns drawish scores when the pawn is
/// far advanced with support of the king, while the attacking king is far
/// away.
template<>
Value Endgame<KRKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
Square wksq = relative_square(strongSide, pos.king_square(strongSide));
Square bksq = relative_square(strongSide, pos.king_square(weakSide));
Square rsq = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
Square psq = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
Square queeningSq = make_square(file_of(psq), RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (wksq < psq && file_of(wksq) == file_of(psq))
result = RookValueEg - distance(wksq, psq);
// If the weaker side's king is too far from the pawn and the rook,
// it's a win.
else if ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
&& distance(bksq, rsq) >= 3)
result = RookValueEg - distance(wksq, psq);
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if ( rank_of(bksq) <= RANK_3
&& distance(bksq, psq) == 1
&& rank_of(wksq) >= RANK_4
&& distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
result = Value(80) - 8 * distance(wksq, psq);
else
result = Value(200) - 8 * ( distance(wksq, psq + DELTA_S)
- distance(bksq, psq + DELTA_S)
- distance(psq, queeningSq));
return strongSide == pos.side_to_move() ? result : -result;
}
/// KR vs KB. This is very simple, and always returns drawish scores. The
/// score is slightly bigger when the defending king is close to the edge.
template<>
Value Endgame<KRKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
Value result = Value(PushToEdges[pos.king_square(weakSide)]);
return strongSide == pos.side_to_move() ? result : -result;
}
/// KR vs KN. The attacking side has slightly better winning chances than
/// in KR vs KB, particularly if the king and the knight are far apart.
template<>
Value Endgame<KRKN>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
Square bksq = pos.king_square(weakSide);
Square bnsq = pos.list<KNIGHT>(weakSide)[0];
Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]);
return strongSide == pos.side_to_move() ? result : -result;
}
/// KQ vs KP. In general, this is a win for the stronger side, but there are a
/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files
/// with a king positioned next to it can be a draw, so in that case, we only
/// use the distance between the kings.
template<>
Value Endgame<KQKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
Square winnerKSq = pos.king_square(strongSide);
Square loserKSq = pos.king_square(weakSide);
Square pawnSq = pos.list<PAWN>(weakSide)[0];
Value result = Value(PushClose[distance(winnerKSq, loserKSq)]);
if ( relative_rank(weakSide, pawnSq) != RANK_7
|| distance(loserKSq, pawnSq) != 1
|| !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
result += QueenValueEg - PawnValueEg;
return strongSide == pos.side_to_move() ? result : -result;
}
/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
/// king a bonus for having the kings close together, and for forcing the
/// defending king towards the edge. If we also take care to avoid null move for
/// the defending side in the search, this is usually sufficient to win KQ vs KR.
template<>
Value Endgame<KQKR>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, RookValueMg, 0));
Square winnerKSq = pos.king_square(strongSide);
Square loserKSq = pos.king_square(weakSide);
Value result = QueenValueEg
- RookValueEg
+ PushToEdges[loserKSq]
+ PushClose[distance(winnerKSq, loserKSq)];
return strongSide == pos.side_to_move() ? result : -result;
}
/// Some cases of trivial draws
template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
/// KB and one or more pawns vs K. It checks for draws with rook pawns and
/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
template<>
ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongSide) == BishopValueMg);
assert(pos.count<PAWN>(strongSide) >= 1);
// No assertions about the material of weakSide, because we want draws to
// be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces(strongSide, PAWN);
File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
// All pawns are on a single rook file ?
if ( (pawnFile == FILE_A || pawnFile == FILE_H)
&& !(pawns & ~file_bb(pawnFile)))
{
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakSide);
if ( opposite_colors(queeningSq, bishopSq)
&& distance(queeningSq, kingSq) <= 1)
return SCALE_FACTOR_DRAW;
}
// If all the pawns are on the same B or G file, then it's potentially a draw
if ( (pawnFile == FILE_B || pawnFile == FILE_G)
&& !(pos.pieces(PAWN) & ~file_bb(pawnFile))
&& pos.non_pawn_material(weakSide) == 0
&& pos.count<PAWN>(weakSide) >= 1)
{
// Get weakSide pawn that is closest to the home rank
Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
Square strongKingSq = pos.king_square(strongSide);
Square weakKingSq = pos.king_square(weakSide);
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
// There's potential for a draw if our pawn is blocked on the 7th rank,
// the bishop cannot attack it or they only have one pawn left
if ( relative_rank(strongSide, weakPawnSq) == RANK_7
&& (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
&& (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
{
int strongKingDist = distance(weakPawnSq, strongKingSq);
int weakKingDist = distance(weakPawnSq, weakKingSq);
// It's a draw if the weak king is on its back two ranks, within 2
// squares of the blocking pawn and the strong king is not
// closer. (I think this rule only fails in practically
// unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
// and positions where qsearch will immediately correct the
// problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
if ( relative_rank(strongSide, weakKingSq) >= RANK_7
&& weakKingDist <= 2
&& weakKingDist <= strongKingDist)
return SCALE_FACTOR_DRAW;
}
}
return SCALE_FACTOR_NONE;
}
/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on
/// the third rank defended by a pawn.
template<>
ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(pos.count<ROOK>(weakSide) == 1);
assert(pos.count<PAWN>(weakSide) >= 1);
Square kingSq = pos.king_square(weakSide);
Square rsq = pos.list<ROOK>(weakSide)[0];
if ( relative_rank(weakSide, kingSq) <= RANK_2
&& relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4
&& relative_rank(weakSide, rsq) == RANK_3
&& ( pos.pieces(weakSide, PAWN)
& pos.attacks_from<KING>(kingSq)
& pos.attacks_from<PAWN>(rsq, strongSide)))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
/// KRP vs KR. This function knows a handful of the most important classes of
/// drawn positions, but is far from perfect. It would probably be a good idea
/// to add more knowledge in the future.
///
/// It would also be nice to rewrite the actual code for this function,
/// which is mostly copied from Glaurung 1.x, and isn't very pretty.
template<>
ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 1));
assert(verify_material(pos, weakSide, RookValueMg, 0));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
File f = file_of(wpsq);
Rank r = rank_of(wpsq);
Square queeningSq = make_square(f, RANK_8);
int tempo = (pos.side_to_move() == strongSide);
// If the pawn is not too far advanced and the defending king defends the
// queening square, use the third-rank defence.
if ( r <= RANK_5
&& distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
&& (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
return SCALE_FACTOR_DRAW;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
if ( r == RANK_6
&& distance(bksq, queeningSq) <= 1
&& rank_of(wksq) + tempo <= RANK_6
&& (rank_of(brsq) == RANK_1 || (!tempo && distance(file_of(brsq), f) >= 3)))
return SCALE_FACTOR_DRAW;
if ( r >= RANK_6
&& bksq == queeningSq
&& rank_of(brsq) == RANK_1
&& (!tempo || distance(wksq, wpsq) >= 2))
return SCALE_FACTOR_DRAW;
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
if ( wpsq == SQ_A7
&& wrsq == SQ_A8
&& (bksq == SQ_H7 || bksq == SQ_G7)
&& file_of(brsq) == FILE_A
&& (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
return SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if ( r <= RANK_5
&& bksq == wpsq + DELTA_N
&& distance(wksq, wpsq) - tempo >= 2
&& distance(wksq, brsq) - tempo >= 2)
return SCALE_FACTOR_DRAW;
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
// and the defending king cannot gain tempi by threatening the attacking rook.
if ( r == RANK_7
&& f != FILE_A
&& file_of(wrsq) == f
&& wrsq != queeningSq
&& (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
&& (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo))
return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq));
// Similar to the above, but with the pawn further back
if ( f != FILE_A
&& file_of(wrsq) == f
&& wrsq < wpsq
&& (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
&& (distance(wksq, wpsq + DELTA_N) < distance(bksq, wpsq + DELTA_N) - 2 + tempo)
&& ( distance(bksq, wrsq) + tempo >= 3
|| ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo
&& (distance(wksq, wpsq + DELTA_N) < distance(bksq, wrsq) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- 8 * distance(wpsq, queeningSq)
- 2 * distance(wksq, queeningSq));
// If the pawn is not far advanced and the defending king is somewhere in
// the pawn's path, it's probably a draw.
if (r <= RANK_4 && bksq > wpsq)
{
if (file_of(bksq) == file_of(wpsq))
return ScaleFactor(10);
if ( distance<File>(bksq, wpsq) == 1
&& distance(wksq, bksq) > 2)
return ScaleFactor(24 - 2 * distance(wksq, bksq));
}
return SCALE_FACTOR_NONE;
}
template<>
ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 1));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
// Test for a rook pawn
if (pos.pieces(PAWN) & (FileABB | FileHBB))
{
Square ksq = pos.king_square(weakSide);
Square bsq = pos.list<BISHOP>(weakSide)[0];
Square psq = pos.list<PAWN>(strongSide)[0];
Rank rk = relative_rank(strongSide, psq);
Square push = pawn_push(strongSide);
// If the pawn is on the 5th rank and the pawn (currently) is on
// the same color square as the bishop then there is a chance of
// a fortress. Depending on the king position give a moderate
// reduction or a stronger one if the defending king is near the
// corner but not trapped there.
if (rk == RANK_5 && !opposite_colors(bsq, psq))
{
int d = distance(psq + 3 * push, ksq);
if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push))
return ScaleFactor(24);
else
return ScaleFactor(48);
}
// When the pawn has moved to the 6th rank we can be fairly sure
// it's drawn if the bishop attacks the square in front of the
// pawn from a reasonable distance and the defending king is near
// the corner
if ( rk == RANK_6
&& distance(psq + 2 * push, ksq) <= 1
&& (PseudoAttacks[BISHOP][bsq] & (psq + push))
&& distance<File>(bsq, psq) >= 2)
return ScaleFactor(8);
}
return SCALE_FACTOR_NONE;
}
/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed
/// pawns and the defending king is actively placed, the position is drawish.
template<>
ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 2));
assert(verify_material(pos, weakSide, RookValueMg, 1));
Square wpsq1 = pos.list<PAWN>(strongSide)[0];
Square wpsq2 = pos.list<PAWN>(strongSide)[1];
Square bksq = pos.king_square(weakSide);
// Does the stronger side have a passed pawn?
if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
return SCALE_FACTOR_NONE;
Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
if ( distance<File>(bksq, wpsq1) <= 1
&& distance<File>(bksq, wpsq2) <= 1
&& relative_rank(strongSide, bksq) > r)
{
switch (r) {
case RANK_2: return ScaleFactor(10);
case RANK_3: return ScaleFactor(10);
case RANK_4: return ScaleFactor(15);
case RANK_5: return ScaleFactor(20);
case RANK_6: return ScaleFactor(40);
default: assert(false);
}
}
return SCALE_FACTOR_NONE;
}
/// K and two or more pawns vs K. There is just a single rule here: If all pawns
/// are on the same rook file and are blocked by the defending king, it's a draw.
template<>
ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongSide) == VALUE_ZERO);
assert(pos.count<PAWN>(strongSide) >= 2);
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
Square ksq = pos.king_square(weakSide);
Bitboard pawns = pos.pieces(strongSide, PAWN);
Square psq = pos.list<PAWN>(strongSide)[0];
// If all pawns are ahead of the king, on a single rook file and
// the king is within one file of the pawns, it's a draw.
if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
&& !((pawns & ~FileABB) && (pawns & ~FileHBB))
&& distance<File>(ksq, psq) <= 1)
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
/// KBP vs KB. There are two rules: if the defending king is somewhere along the
/// path of the pawn, and the square of the king is not of the same color as the
/// stronger side's bishop, it's a draw. If the two bishops have opposite color,
/// it's almost always a draw.
template<>
ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
Square pawnSq = pos.list<PAWN>(strongSide)[0];
Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
Square weakBishopSq = pos.list<BISHOP>(weakSide)[0];
Square weakKingSq = pos.king_square(weakSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if ( file_of(weakKingSq) == file_of(pawnSq)
&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
&& ( opposite_colors(weakKingSq, strongBishopSq)
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
if (opposite_colors(strongBishopSq, weakBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// a. The pawn is on rank 5 or further back.
// b. The defending king is somewhere in the pawn's path.
// c. The defending bishop attacks some square along the pawn's path,
// and is at least three squares away from the pawn.
//
// These rules are probably not perfect, but in practice they work
// reasonably well.
if (relative_rank(strongSide, pawnSq) <= RANK_5)
return SCALE_FACTOR_DRAW;
else
{
Bitboard path = forward_bb(strongSide, pawnSq);
if (path & pos.pieces(weakSide, KING))
return SCALE_FACTOR_DRAW;
if ( (pos.attacks_from<BISHOP>(weakBishopSq) & path)
&& distance(weakBishopSq, pawnSq) >= 3)
return SCALE_FACTOR_DRAW;
}
}
return SCALE_FACTOR_NONE;
}
/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
template<>
ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 2));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
Square wbsq = pos.list<BISHOP>(strongSide)[0];
Square bbsq = pos.list<BISHOP>(weakSide)[0];
if (!opposite_colors(wbsq, bbsq))
return SCALE_FACTOR_NONE;
Square ksq = pos.king_square(weakSide);
Square psq1 = pos.list<PAWN>(strongSide)[0];
Square psq2 = pos.list<PAWN>(strongSide)[1];
Rank r1 = rank_of(psq1);
Rank r2 = rank_of(psq2);
Square blockSq1, blockSq2;
if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
{
blockSq1 = psq1 + pawn_push(strongSide);
blockSq2 = make_square(file_of(psq2), rank_of(psq1));
}
else
{
blockSq1 = psq2 + pawn_push(strongSide);
blockSq2 = make_square(file_of(psq1), rank_of(psq2));
}
switch (distance<File>(psq1, psq2))
{
case 0:
// Both pawns are on the same file. It's an easy draw if the defender firmly
// controls some square in the frontmost pawn's path.
if ( file_of(ksq) == file_of(blockSq1)
&& relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
&& opposite_colors(ksq, wbsq))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
case 1:
// Pawns on adjacent files. It's a draw if the defender firmly controls the
// square in front of the frontmost pawn's path, and the square diagonally
// behind this square on the file of the other pawn.
if ( ksq == blockSq1
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq2
|| (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
|| distance(r1, r2) >= 2))
return SCALE_FACTOR_DRAW;
else if ( ksq == blockSq2
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq1
|| (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
default:
// The pawns are not on the same file or adjacent files. No scaling.
return SCALE_FACTOR_NONE;
}
}
/// KBP vs KN. There is a single rule: If the defending king is somewhere along
/// the path of the pawn, and the square of the king is not of the same color as
/// the stronger side's bishop, it's a draw.
template<>
ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
Square pawnSq = pos.list<PAWN>(strongSide)[0];
Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
Square weakKingSq = pos.king_square(weakSide);
if ( file_of(weakKingSq) == file_of(pawnSq)
&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
&& ( opposite_colors(weakKingSq, strongBishopSq)
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
/// KNP vs K. There is a single rule: if the pawn is a rook pawn on the 7th rank
/// and the defending king prevents the pawn from advancing, the position is drawn.
template<>
ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, KnightValueMg, 1));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
// Assume strongSide is white and the pawn is on files A-D
Square pawnSq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1)
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
/// Otherwise the position is drawn.
template<>
ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
Square pawnSq = pos.list<PAWN>(strongSide)[0];
Square bishopSq = pos.list<BISHOP>(weakSide)[0];
Square weakKingSq = pos.king_square(weakSide);
// King needs to get close to promoting pawn to prevent knight from blocking.
// Rules for this are very tricky, so just approximate.
if (forward_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
return ScaleFactor(distance(weakKingSq, pawnSq));
return SCALE_FACTOR_NONE;
}
/// KP vs KP. This is done by removing the weakest side's pawn and probing the
/// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably
/// has at least a draw with the pawn as well. The exception is when the stronger
/// side's pawn is far advanced and not on a rook file; in this case it is often
/// possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
template<>
ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
// If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw.
if (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A)
return SCALE_FACTOR_NONE;
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
// it's probably at least a draw even with the pawn.
return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}

121
src/endgame.h
View file

@ -1,121 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef ENDGAME_H_INCLUDED
#define ENDGAME_H_INCLUDED
#include <map>
#include <string>
#include "position.h"
#include "types.h"
/// EndgameType lists all supported endgames
enum EndgameType {
// Evaluation functions
KNNK, // KNN vs K
KXK, // Generic "mate lone king" eval
KBNK, // KBN vs K
KPK, // KP vs K
KRKP, // KR vs KP
KRKB, // KR vs KB
KRKN, // KR vs KN
KQKP, // KQ vs KP
KQKR, // KQ vs KR
// Scaling functions
SCALE_FUNS,
KBPsK, // KB and pawns vs K
KQKRPs, // KQ vs KR and pawns
KRPKR, // KRP vs KR
KRPKB, // KRP vs KB
KRPPKRP, // KRPP vs KRP
KPsK, // K and pawns vs K
KBPKB, // KBP vs KB
KBPPKB, // KBPP vs KB
KBPKN, // KBP vs KN
KNPK, // KNP vs K
KNPKB, // KNP vs KB
KPKP // KP vs KP
};
/// Endgame functions can be of two types depending on whether they return a
/// Value or a ScaleFactor. Type eg_fun<int>::type returns either ScaleFactor
/// or Value depending on whether the template parameter is 0 or 1.
template<int> struct eg_fun { typedef Value type; };
template<> struct eg_fun<1> { typedef ScaleFactor type; };
/// Base and derived templates for endgame evaluation and scaling functions
template<typename T>
struct EndgameBase {
virtual ~EndgameBase() {}
virtual Color strong_side() const = 0;
virtual T operator()(const Position&) const = 0;
};
template<EndgameType E, typename T = typename eg_fun<(E > SCALE_FUNS)>::type>
struct Endgame : public EndgameBase<T> {
explicit Endgame(Color c) : strongSide(c), weakSide(~c) {}
Color strong_side() const { return strongSide; }
T operator()(const Position&) const;
private:
const Color strongSide, weakSide;
};
/// The Endgames class stores the pointers to endgame evaluation and scaling
/// base objects in two std::map typedefs. We then use polymorphism to invoke
/// the actual endgame function by calling its virtual operator().
class Endgames {
typedef std::map<Key, EndgameBase<eg_fun<0>::type>*> M1;
typedef std::map<Key, EndgameBase<eg_fun<1>::type>*> M2;
M1 m1;
M2 m2;
M1& map(M1::mapped_type) { return m1; }
M2& map(M2::mapped_type) { return m2; }
template<EndgameType E> void add(const std::string& code);
public:
Endgames();
~Endgames();
template<typename T> T probe(Key key, T& eg)
{ return eg = map(eg).count(key) ? map(eg)[key] : NULL; }
};
#endif // #ifndef ENDGAME_H_INCLUDED

905
src/evaluate.cpp
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@ -1,905 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include <cassert>
#include <cstring> // For std::memset
#include <iomanip>
#include <sstream>
#include "bitcount.h"
#include "evaluate.h"
#include "material.h"
#include "pawns.h"
namespace {
// Struct EvalInfo contains various information computed and collected
// by the evaluation functions.
struct EvalInfo {
// Pointers to material and pawn hash table entries
Material::Entry* mi;
Pawns::Entry* pi;
// attackedBy[color][piece type] is a bitboard representing all squares
// attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
// contains all squares attacked by the given color.
Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
// kingRing[color] is the zone around the king which is considered
// by the king safety evaluation. This consists of the squares directly
// adjacent to the king, and the three (or two, for a king on an edge file)
// squares two ranks in front of the king. For instance, if black's king
// is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
// f7, g7, h7, f6, g6 and h6.
Bitboard kingRing[COLOR_NB];
// kingAttackersCount[color] is the number of pieces of the given color
// which attack a square in the kingRing of the enemy king.
int kingAttackersCount[COLOR_NB];
// kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
// given color which attack a square in the kingRing of the enemy king. The
// weights of the individual piece types are given by the elements in the
// KingAttackWeights array.
int kingAttackersWeight[COLOR_NB];
// kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
// directly adjacent to the king of the given color. Pieces which attack
// more than one square are counted multiple times. For instance, if black's
// king is on g8 and there's a white knight on g5, this knight adds
// 2 to kingAdjacentZoneAttacksCount[BLACK].
int kingAdjacentZoneAttacksCount[COLOR_NB];
Bitboard pinnedPieces[COLOR_NB];
};
namespace Tracing {
enum Terms { // First 8 entries are for PieceType
MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
};
Score scores[COLOR_NB][TERMS_NB];
EvalInfo ei;
ScaleFactor sf;
double to_cp(Value v);
void write(int idx, Color c, Score s);
void write(int idx, Score w, Score b = SCORE_ZERO);
void print(std::stringstream& ss, const char* name, int idx);
std::string do_trace(const Position& pos);
}
// Evaluation weights, indexed by evaluation term
enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
const struct Weight { int mg, eg; } Weights[] = {
{289, 344}, {233, 201}, {221, 273}, {46, 0}, {321, 0}
};
#define V(v) Value(v)
#define S(mg, eg) make_score(mg, eg)
// MobilityBonus[PieceType][attacked] contains bonuses for middle and end
// game, indexed by piece type and number of attacked squares not occupied by
// friendly pieces.
const Score MobilityBonus[][32] = {
{}, {},
{ S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
S( 37, 28), S( 42, 31), S(44, 33) },
{ S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
S( 84, 79), S( 86, 81) },
{ S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
S( 35,122), S( 36,123), S(37,124) },
{ S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
};
// Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
// indexed by piece type and square (from white's point of view).
const Value Outpost[][SQUARE_NB] = {
{// A B C D E F G H
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
{
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
};
// Threat[defended/weak][minor/major attacking][attacked PieceType] contains
// bonuses according to which piece type attacks which one.
const Score Threat[][2][PIECE_TYPE_NB] = {
{ { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
{ S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
{ { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
{ S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
};
// ThreatenedByPawn[PieceType] contains a penalty according to which piece
// type is attacked by an enemy pawn.
const Score ThreatenedByPawn[] = {
S(0, 0), S(0, 0), S(87, 118), S(84, 122), S(114, 203), S(121, 217)
};
// Assorted bonuses and penalties used by evaluation
const Score KingOnOne = S( 2, 58);
const Score KingOnMany = S( 6,125);
const Score RookOnPawn = S( 7, 27);
const Score RookOnOpenFile = S(43, 21);
const Score RookOnSemiOpenFile = S(19, 10);
const Score BishopPawns = S( 8, 12);
const Score MinorBehindPawn = S(16, 0);
const Score TrappedRook = S(92, 0);
const Score Unstoppable = S( 0, 20);
const Score Hanging = S(31, 26);
// Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
// a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
// happen in Chess960 games.
const Score TrappedBishopA1H1 = S(50, 50);
#undef S
#undef V
// SpaceMask[Color] contains the area of the board which is considered
// by the space evaluation. In the middlegame, each side is given a bonus
// based on how many squares inside this area are safe and available for
// friendly minor pieces.
const Bitboard SpaceMask[] = {
(FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
(FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
};
// King danger constants and variables. The king danger scores are looked-up
// in KingDanger[]. Various little "meta-bonuses" measuring the strength
// of the enemy attack are added up into an integer, which is used as an
// index to KingDanger[].
//
// KingAttackWeights[PieceType] contains king attack weights by piece type
const int KingAttackWeights[] = { 0, 0, 6, 2, 5, 5 };
// Bonuses for enemy's safe checks
const int QueenContactCheck = 92;
const int RookContactCheck = 68;
const int QueenCheck = 50;
const int RookCheck = 36;
const int BishopCheck = 7;
const int KnightCheck = 14;
// KingDanger[attackUnits] contains the actual king danger weighted
// scores, indexed by a calculated integer number.
Score KingDanger[512];
// apply_weight() weighs score 's' by weight 'w' trying to prevent overflow
Score apply_weight(Score s, const Weight& w) {
return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
}
// init_eval_info() initializes king bitboards for given color adding
// pawn attacks. To be done at the beginning of the evaluation.
template<Color Us>
void init_eval_info(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
// Init king safety tables only if we are going to use them
if (pos.non_pawn_material(Us) >= QueenValueMg)
{
ei.kingRing[Them] = b | shift_bb<Down>(b);
b &= ei.attackedBy[Us][PAWN];
ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
}
else
ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
}
// evaluate_outpost() evaluates bishop and knight outpost squares
template<PieceType Pt, Color Us>
Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
assert (Pt == BISHOP || Pt == KNIGHT);
// Initial bonus based on square
Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
// Increase bonus if supported by pawn, especially if the opponent has
// no minor piece which can trade with the outpost piece.
if (bonus && (ei.attackedBy[Us][PAWN] & s))
{
if ( !pos.pieces(Them, KNIGHT)
&& !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
bonus += bonus + bonus / 2;
else
bonus += bonus / 2;
}
return make_score(bonus * 2, bonus / 2);
}
// evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
template<PieceType Pt, Color Us, bool Trace>
Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
Bitboard b;
Square s;
Score score = SCORE_ZERO;
const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square* pl = pos.list<Pt>(Us);
ei.attackedBy[Us][Pt] = 0;
while ((s = *pl++) != SQ_NONE)
{
// Find attacked squares, including x-ray attacks for bishops and rooks
b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
: pos.attacks_from<Pt>(s);
if (ei.pinnedPieces[Us] & s)
b &= LineBB[pos.king_square(Us)][s];
ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
if (b & ei.kingRing[Them])
{
ei.kingAttackersCount[Us]++;
ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
Bitboard bb = b & ei.attackedBy[Them][KING];
if (bb)
ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
}
if (Pt == QUEEN)
b &= ~( ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP]
| ei.attackedBy[Them][ROOK]);
int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
: popcount<Full >(b & mobilityArea[Us]);
mobility[Us] += MobilityBonus[Pt][mob];
// Decrease score if we are attacked by an enemy pawn. The remaining part
// of threat evaluation must be done later when we have full attack info.
if (ei.attackedBy[Them][PAWN] & s)
score -= ThreatenedByPawn[Pt];
if (Pt == BISHOP || Pt == KNIGHT)
{
// Bonus for outpost square
if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
score += evaluate_outpost<Pt, Us>(pos, ei, s);
// Bonus when behind a pawn
if ( relative_rank(Us, s) < RANK_5
&& (pos.pieces(PAWN) & (s + pawn_push(Us))))
score += MinorBehindPawn;
// Penalty for pawns on same color square of bishop
if (Pt == BISHOP)
score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
// An important Chess960 pattern: A cornered bishop blocked by a friendly
// pawn diagonally in front of it is a very serious problem, especially
// when that pawn is also blocked.
if ( Pt == BISHOP
&& pos.is_chess960()
&& (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
{
Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
if (pos.piece_on(s + d) == make_piece(Us, PAWN))
score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
: pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
: TrappedBishopA1H1;
}
}
if (Pt == ROOK)
{
// Bonus for aligning with enemy pawns on the same rank/file
if (relative_rank(Us, s) >= RANK_5)
{
Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
if (alignedPawns)
score += popcount<Max15>(alignedPawns) * RookOnPawn;
}
// Bonus when on an open or semi-open file
if (ei.pi->semiopen_file(Us, file_of(s)))
score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
// Penalize when trapped by the king, even more if king cannot castle
if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
{
Square ksq = pos.king_square(Us);
if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
&& (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
&& !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
}
}
}
if (Trace)
Tracing::write(Pt, Us, score);
// Recursively call evaluate_pieces() of next piece type until KING excluded
return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
}
template<>
Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
template<>
Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
// evaluate_king() assigns bonuses and penalties to a king of a given color
template<Color Us, bool Trace>
Score evaluate_king(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard undefended, b, b1, b2, safe;
int attackUnits;
const Square ksq = pos.king_square(Us);
// King shelter and enemy pawns storm
Score score = ei.pi->king_safety<Us>(pos, ksq);
// Main king safety evaluation
if (ei.kingAttackersCount[Them])
{
// Find the attacked squares around the king which have no defenders
// apart from the king itself
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
& ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
| ei.attackedBy[Us][QUEEN]);
// Initialize the 'attackUnits' variable, which is used later on as an
// index into the KingDanger[] array. The initial value is based on the
// number and types of the enemy's attacking pieces, the number of
// attacked and undefended squares around our king and the quality of
// the pawn shelter (current 'score' value).
attackUnits = std::min(77, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
+ 10 * ei.kingAdjacentZoneAttacksCount[Them]
+ 19 * popcount<Max15>(undefended)
+ 9 * (ei.pinnedPieces[Us] != 0)
- mg_value(score) * 63 / 512
- !pos.count<QUEEN>(Them) * 60;
// Analyse the enemy's safe queen contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy queen...
b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
if (b)
{
// ...and then remove squares not supported by another enemy piece
b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
if (b)
attackUnits += QueenContactCheck * popcount<Max15>(b);
}
// Analyse the enemy's safe rook contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy rooks...
b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
// Consider only squares where the enemy's rook gives check
b &= PseudoAttacks[ROOK][ksq];
if (b)
{
// ...and then remove squares not supported by another enemy piece
b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
if (b)
attackUnits += RookContactCheck * popcount<Max15>(b);
}
// Analyse the enemy's safe distance checks for sliders and knights
safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
b1 = pos.attacks_from<ROOK >(ksq) & safe;
b2 = pos.attacks_from<BISHOP>(ksq) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
if (b)
attackUnits += QueenCheck * popcount<Max15>(b);
// Enemy rooks safe checks
b = b1 & ei.attackedBy[Them][ROOK];
if (b)
attackUnits += RookCheck * popcount<Max15>(b);
// Enemy bishops safe checks
b = b2 & ei.attackedBy[Them][BISHOP];
if (b)
attackUnits += BishopCheck * popcount<Max15>(b);
// Enemy knights safe checks
b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
if (b)
attackUnits += KnightCheck * popcount<Max15>(b);
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation.
score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
}
if (Trace)
Tracing::write(KING, Us, score);
return score;
}
// evaluate_threats() assigns bonuses according to the type of attacking piece
// and the type of attacked one.
template<Color Us, bool Trace>
Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
enum { Defended, Weak };
enum { Minor, Major };
Bitboard b, weak, defended;
Score score = SCORE_ZERO;
// Non-pawn enemies defended by a pawn
defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
& ei.attackedBy[Them][PAWN];
// Add a bonus according to the kind of attacking pieces
if (defended)
{
b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
while (b)
score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
b = defended & (ei.attackedBy[Us][ROOK]);
while (b)
score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
}
// Enemies not defended by a pawn and under our attack
weak = pos.pieces(Them)
& ~ei.attackedBy[Them][PAWN]
& ei.attackedBy[Us][ALL_PIECES];
// Add a bonus according to the kind of attacking pieces
if (weak)
{
b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
while (b)
score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
while (b)
score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
b = weak & ~ei.attackedBy[Them][ALL_PIECES];
if (b)
score += Hanging * popcount<Max15>(b);
b = weak & ei.attackedBy[Us][KING];
if (b)
score += more_than_one(b) ? KingOnMany : KingOnOne;
}
if (Trace)
Tracing::write(Tracing::THREAT, Us, score);
return score;
}
// evaluate_passed_pawns() evaluates the passed pawns of the given color
template<Color Us, bool Trace>
Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
Score score = SCORE_ZERO;
b = ei.pi->passed_pawns(Us);
while (b)
{
Square s = pop_lsb(&b);
assert(pos.pawn_passed(Us, s));
int r = relative_rank(Us, s) - RANK_2;
int rr = r * (r - 1);
// Base bonus based on rank
Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
if (rr)
{
Square blockSq = s + pawn_push(Us);
// Adjust bonus based on the king's proximity
ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
- distance(pos.king_square(Us ), blockSq) * 2 * rr;
// If blockSq is not the queening square then consider also a second push
if (relative_rank(Us, blockSq) != RANK_8)
ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
// If the pawn is free to advance, then increase the bonus
if (pos.empty(blockSq))
{
// If there is a rook or queen attacking/defending the pawn from behind,
// consider all the squaresToQueen. Otherwise consider only the squares
// in the pawn's path attacked or occupied by the enemy.
defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
if (!(pos.pieces(Us) & bb))
defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
if (!(pos.pieces(Them) & bb))
unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
// If there aren't any enemy attacks, assign a big bonus. Otherwise
// assign a smaller bonus if the block square isn't attacked.
int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
// If the path to queen is fully defended, assign a big bonus.
// Otherwise assign a smaller bonus if the block square is defended.
if (defendedSquares == squaresToQueen)
k += 6;
else if (defendedSquares & blockSq)
k += 4;
mbonus += k * rr, ebonus += k * rr;
}
else if (pos.pieces(Us) & blockSq)
mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
} // rr != 0
if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
ebonus += ebonus / 4;
score += make_score(mbonus, ebonus);
}
if (Trace)
Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
// Add the scores to the middlegame and endgame eval
return apply_weight(score, Weights[PassedPawns]);
}
// evaluate_space() computes the space evaluation for a given side. The
// space evaluation is a simple bonus based on the number of safe squares
// available for minor pieces on the central four files on ranks 2--4. Safe
// squares one, two or three squares behind a friendly pawn are counted
// twice. Finally, the space bonus is multiplied by a weight. The aim is to
// improve play on game opening.
template<Color Us>
Score evaluate_space(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
// Find the safe squares for our pieces inside the area defined by
// SpaceMask[]. A square is unsafe if it is attacked by an enemy
// pawn, or if it is undefended and attacked by an enemy piece.
Bitboard safe = SpaceMask[Us]
& ~pos.pieces(Us, PAWN)
& ~ei.attackedBy[Them][PAWN]
& (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
// Find all squares which are at most three squares behind some friendly pawn
Bitboard behind = pos.pieces(Us, PAWN);
behind |= (Us == WHITE ? behind >> 8 : behind << 8);
behind |= (Us == WHITE ? behind >> 16 : behind << 16);
// Since SpaceMask[Us] is fully on our half of the board
assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
// Count safe + (behind & safe) with a single popcount
int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
+ pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
return make_score(bonus * weight * weight, 0);
}
// do_evaluate() is the evaluation entry point, called directly from evaluate()
template<bool Trace>
Value do_evaluate(const Position& pos) {
assert(!pos.checkers());
EvalInfo ei;
Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables).
// Score is computed from the point of view of white.
score = pos.psq_score();
// Probe the material hash table
ei.mi = Material::probe(pos);
score += ei.mi->imbalance();
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (ei.mi->specialized_eval_exists())
return ei.mi->evaluate(pos);
// Probe the pawn hash table
ei.pi = Pawns::probe(pos);
score += apply_weight(ei.pi->pawns_score(), Weights[PawnStructure]);
// Initialize attack and king safety bitboards
init_eval_info<WHITE>(pos, ei);
init_eval_info<BLACK>(pos, ei);
ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
// Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
// Evaluate pieces and mobility
score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king<WHITE, Trace>(pos, ei)
- evaluate_king<BLACK, Trace>(pos, ei);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats<WHITE, Trace>(pos, ei)
- evaluate_threats<BLACK, Trace>(pos, ei);
// Evaluate passed pawns, we need full attack information including king
score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
- evaluate_passed_pawns<BLACK, Trace>(pos, ei);
// If both sides have only pawns, score for potential unstoppable pawns
if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
{
Bitboard b;
if ((b = ei.pi->passed_pawns(WHITE)) != 0)
score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
if ((b = ei.pi->passed_pawns(BLACK)) != 0)
score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
}
// Evaluate space for both sides, only during opening
if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)
{
Score s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
score += apply_weight(s, Weights[Space]);
}
// Scale winning side if position is more drawish than it appears
Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
// If we don't already have an unusual scale factor, check for certain
// types of endgames, and use a lower scale for those.
if ( ei.mi->game_phase() < PHASE_MIDGAME
&& (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
{
if (pos.opposite_bishops())
{
// Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
// is almost a draw, in case of KBP vs KB is even more a draw.
if ( pos.non_pawn_material(WHITE) == BishopValueMg
&& pos.non_pawn_material(BLACK) == BishopValueMg)
sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
// Endgame with opposite-colored bishops, but also other pieces. Still
// a bit drawish, but not as drawish as with only the two bishops.
else
sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
}
// Endings where weaker side can place his king in front of the opponent's
// pawns are drawish.
else if ( abs(eg_value(score)) <= BishopValueEg
&& ei.pi->pawn_span(strongSide) <= 1
&& !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
}
// Interpolate between a middlegame and a (scaled by 'sf') endgame score
Value v = mg_value(score) * int(ei.mi->game_phase())
+ eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
v /= int(PHASE_MIDGAME);
// In case of tracing add all single evaluation contributions for both white and black
if (Trace)
{
Tracing::write(Tracing::MATERIAL, pos.psq_score());
Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
Tracing::write(PAWN, ei.pi->pawns_score());
Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
, apply_weight(mobility[BLACK], Weights[Mobility]));
Tracing::write(Tracing::SPACE, apply_weight(evaluate_space<WHITE>(pos, ei), Weights[Space])
, apply_weight(evaluate_space<BLACK>(pos, ei), Weights[Space]));
Tracing::write(Tracing::TOTAL, score);
Tracing::ei = ei;
Tracing::sf = sf;
}
return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
}
// Tracing function definitions
double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
void Tracing::write(int idx, Score w, Score b) {
write(idx, WHITE, w);
write(idx, BLACK, b);
}
void Tracing::print(std::stringstream& ss, const char* name, int idx) {
Score wScore = scores[WHITE][idx];
Score bScore = scores[BLACK][idx];
switch (idx) {
case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
ss << std::setw(15) << name << " | --- --- | --- --- | "
<< std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
<< std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
break;
default:
ss << std::setw(15) << name << " | " << std::noshowpos
<< std::setw(5) << to_cp(mg_value(wScore)) << " "
<< std::setw(5) << to_cp(eg_value(wScore)) << " | "
<< std::setw(5) << to_cp(mg_value(bScore)) << " "
<< std::setw(5) << to_cp(eg_value(bScore)) << " | "
<< std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
<< std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
}
}
std::string Tracing::do_trace(const Position& pos) {
std::memset(scores, 0, sizeof(scores));
Value v = do_evaluate<true>(pos);
v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
std::stringstream ss;
ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
<< " Eval term | White | Black | Total \n"
<< " | MG EG | MG EG | MG EG \n"
<< "----------------+-------------+-------------+-------------\n";
print(ss, "Material", MATERIAL);
print(ss, "Imbalance", IMBALANCE);
print(ss, "Pawns", PAWN);
print(ss, "Knights", KNIGHT);
print(ss, "Bishops", BISHOP);
print(ss, "Rooks", ROOK);
print(ss, "Queens", QUEEN);
print(ss, "Mobility", MOBILITY);
print(ss, "King safety", KING);
print(ss, "Threats", THREAT);
print(ss, "Passed pawns", PASSED);
print(ss, "Space", SPACE);
ss << "----------------+-------------+-------------+-------------\n";
print(ss, "Total", TOTAL);
ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
return ss.str();
}
} // namespace
namespace Eval {
/// evaluate() is the main evaluation function. It returns a static evaluation
/// of the position always from the point of view of the side to move.
Value evaluate(const Position& pos) {
return do_evaluate<false>(pos);
}
/// trace() is like evaluate(), but instead of returning a value, it returns
/// a string (suitable for outputting to stdout) that contains the detailed
/// descriptions and values of each evaluation term. It's mainly used for
/// debugging.
std::string trace(const Position& pos) {
return Tracing::do_trace(pos);
}
/// init() computes evaluation weights, usually at startup
void init() {
const double MaxSlope = 7.5;
const double Peak = 1280;
double t = 0.0;
for (int i = 1; i < 400; ++i)
{
t = std::min(Peak, std::min(0.025 * i * i, t + MaxSlope));
KingDanger[i] = apply_weight(make_score(int(t), 0), Weights[KingSafety]);
}
}
} // namespace Eval

37
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@ -1,37 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef EVALUATE_H_INCLUDED
#define EVALUATE_H_INCLUDED
#include "types.h"
class Position;
namespace Eval {
const Value Tempo = Value(17); // Must be visible to search
void init();
Value evaluate(const Position& pos);
std::string trace(const Position& pos);
}
#endif // #ifndef EVALUATE_H_INCLUDED

238
src/material.cpp
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@ -1,238 +0,0 @@
/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm> // For std::min
#include <cassert>
#include <cstring> // For std::memset
#include "material.h"
#include "thread.h"
using namespace std;
namespace {
// Polynomial material imbalance parameters
// pair pawn knight bishop rook queen
const int Linear[6] = { 1852, -162, -1122, -183, 249, -154 };
const int QuadraticOurs[][PIECE_TYPE_NB] = {
// OUR PIECES
// pair pawn knight bishop rook queen
{ 0 }, // Bishop pair
{ 39, 2 }, // Pawn
{ 35, 271, -4 }, // Knight OUR PIECES
{ 0, 105, 4, 0 }, // Bishop
{ -27, -2, 46, 100, -141 }, // Rook
{-177, 25, 129, 142, -137, 0 } // Queen
};
const int QuadraticTheirs[][PIECE_TYPE_NB] = {
// THEIR PIECES
// pair pawn knight bishop rook queen
{ 0 }, // Bishop pair
{ 37, 0 }, // Pawn
{ 10, 62, 0 }, // Knight OUR PIECES
{ 57, 64, 39, 0 }, // Bishop
{ 50, 40, 23, -22, 0 }, // Rook
{ 98, 105, -39, 141, 274, 0 } // Queen
};
// Endgame evaluation and scaling functions are accessed directly and not through
// the function maps because they correspond to more than one material hash key.
Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
Endgame<KQKRPs> ScaleKQKRPs[] = { Endgame<KQKRPs>(WHITE), Endgame<KQKRPs>(BLACK) };
Endgame<KPsK> ScaleKPsK[] = { Endgame<KPsK>(WHITE), Endgame<KPsK>(BLACK) };
Endgame<KPKP> ScaleKPKP[] = { Endgame<KPKP>(WHITE), Endgame<KPKP>(BLACK) };
// Helper templates used to detect a given material distribution
template<Color Us> bool is_KXK(const Position& pos) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
return !more_than_one(pos.pieces(Them))
&& pos.non_pawn_material(Us) >= RookValueMg;
}
template<Color Us> bool is_KBPsKs(const Position& pos) {
return pos.non_pawn_material(Us) == BishopValueMg
&& pos.count<BISHOP>(Us) == 1
&& pos.count<PAWN >(Us) >= 1;
}
template<Color Us> bool is_KQKRPs(const Position& pos) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
return !pos.count<PAWN>(Us)
&& pos.non_pawn_material(Us) == QueenValueMg
&& pos.count<QUEEN>(Us) == 1
&& pos.count<ROOK>(Them) == 1
&& pos.count<PAWN>(Them) >= 1;
}
/// imbalance() calculates the imbalance by comparing the piece count of each
/// piece type for both colors.
template<Color Us>
int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
int bonus = 0;
// Second-degree polynomial material imbalance by Tord Romstad
for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
{
if (!pieceCount[Us][pt1])
continue;
int v = Linear[pt1];
for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
v += QuadraticOurs[pt1][pt2] * pieceCount[Us][pt2]
+ QuadraticTheirs[pt1][pt2] * pieceCount[Them][pt2];
bonus += pieceCount[Us][pt1] * v;
}
return bonus;
}
} // namespace
namespace Material {
/// Material::probe() looks up the current position's material configuration in
/// the material 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 material configuration occurs again.
Entry* probe(const Position& pos) {
Key key = pos.material_key();
Entry* e = pos.this_thread()->materialTable[key];
if (e->key == key)
return e;
std::memset(e, 0, sizeof(Entry));
e->key = key;
e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
e->gamePhase = pos.game_phase();
// Let's look if we have a specialized evaluation function for this particular
// material configuration. Firstly we look for a fixed configuration one, then
// for a generic one if the previous search failed.
if (pos.this_thread()->endgames.probe(key, e->evaluationFunction))
return e;
if (is_KXK<WHITE>(pos))
{
e->evaluationFunction = &EvaluateKXK[WHITE];
return e;
}
if (is_KXK<BLACK>(pos))
{
e->evaluationFunction = &EvaluateKXK[BLACK];
return e;
}
// OK, we didn't find any special evaluation function for the current material
// configuration. Is there a suitable specialized scaling function?
EndgameBase<ScaleFactor>* sf;
if (pos.this_thread()->endgames.probe(key, sf))
{
e->scalingFunction[sf->strong_side()] = sf; // Only strong color assigned
return e;
}
// We didn't find any specialized scaling function, so fall back on generic
// ones that refer to more than one material distribution. Note that in this
// case we don't return after setting the function.
if (is_KBPsKs<WHITE>(pos))
e->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
if (is_KBPsKs<BLACK>(pos))
e->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
if (is_KQKRPs<WHITE>(pos))
e->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
else if (is_KQKRPs<BLACK>(pos))
e->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
Value npm_w = pos.non_pawn_material(WHITE);
Value npm_b = pos.non_pawn_material(BLACK);
if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN)) // Only pawns on the board
{
if (!pos.count<PAWN>(BLACK))
{
assert(pos.count<PAWN>(WHITE) >= 2);
e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
}
else if (!pos.count<PAWN>(WHITE))
{
assert(pos.count<PAWN>(BLACK) >= 2);
e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
}
else if (pos.count<PAWN>(WHITE) == 1 && pos.count<PAWN>(BLACK) == 1)
{
// This is a special case because we set scaling functions
// for both colors instead of only one.
e->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
e->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
}
}
// Zero or just one pawn makes it difficult to win, even with a small material
// advantage. This catches some trivial draws like KK, KBK and KNK and gives a
// drawish scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW :
npm_b <= BishopValueMg ? 4 : 12);
if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW :
npm_w <= BishopValueMg ? 4 : 12);
if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
// for the bishop pair "extended piece", which allows us to be more flexible
// in defining bishop pair bonuses.
const int PieceCount[COLOR_NB][PIECE_TYPE_NB] = {
{ pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
pos.count<BISHOP>(WHITE) , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
{ pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
pos.count<BISHOP>(BLACK) , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
e->value = int16_t((imbalance<WHITE>(PieceCount) - imbalance<BLACK>(PieceCount)) / 16);
return e;
}
} // namespace Material

72
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/*
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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MATERIAL_H_INCLUDED
#define MATERIAL_H_INCLUDED
#include "endgame.h"
#include "misc.h"
#include "position.h"
#include "types.h"
namespace Material {
/// Material::Entry contains various information about a material configuration.
/// It contains a material imbalance evaluation, a function pointer to a special
/// endgame evaluation function (which in most cases is NULL, meaning that the
/// standard evaluation function will be used), and scale factors.
///
/// The scale factors are used to scale the evaluation score up or down. For
/// instance, in KRB vs KR endgames, the score is scaled down by a factor of 4,
/// which will result in scores of absolute value less than one pawn.
struct Entry {
Score imbalance() const { return make_score(value, value); }
Phase game_phase() const { return gamePhase; }
bool specialized_eval_exists() const { return evaluationFunction != NULL; }
Value evaluate(const Position& pos) const { return (*evaluationFunction)(pos); }
// scale_factor takes a position and a color as input and returns a scale factor
// for the given color. We have to provide the position in addition to the color
// because the scale factor may also be a function which should be applied to
// the position. For instance, in KBP vs K endgames, the scaling function looks
// for rook pawns and wrong-colored bishops.
ScaleFactor scale_factor(const Position& pos, Color c) const {
return !scalingFunction[c] || (*scalingFunction[c])(pos) == SCALE_FACTOR_NONE
? ScaleFactor(factor[c]) : (*scalingFunction[c])(pos);
}
Key key;
int16_t value;
uint8_t factor[COLOR_NB];
EndgameBase<Value>* evaluationFunction;
EndgameBase<ScaleFactor>* scalingFunction[COLOR_NB]; // Could be one for each
// side (e.g. KPKP, KBPsKs)
Phase gamePhase;
};
typedef HashTable<Entry, 8192> Table;
Entry* probe(const Position& pos);
} // namespace Material
#endif // #ifndef MATERIAL_H_INCLUDED