/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (c) 2013 Ronald de Man
- Copyright (C) 2016-2018 Marco Costalba, Lucas Braesch
+ Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
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 <fstream>
#include <iostream>
#include <list>
+#include <mutex>
#include <sstream>
+#include <string_view>
#include <type_traits>
#include "../bitboard.h"
#include "../movegen.h"
#include "../position.h"
#include "../search.h"
-#include "../thread_win32.h"
#include "../types.h"
#include "../uci.h"
#include <sys/stat.h>
#else
#define WIN32_LEAN_AND_MEAN
-#define NOMINMAX
+#ifndef NOMINMAX
+# define NOMINMAX // Disable macros min() and max()
+#endif
#include <windows.h>
#endif
-using namespace Tablebases;
+using namespace Stockfish::Tablebases;
+
+int Stockfish::Tablebases::MaxCardinality;
-int Tablebases::MaxCardinality;
+namespace Stockfish {
namespace {
constexpr int TBPIECES = 7; // Max number of supported pieces
+constexpr int MAX_DTZ = 1 << 18; // Max DTZ supported, large enough to deal with the syzygy TB limit.
enum { BigEndian, LittleEndian };
-enum TBType { KEY, WDL, DTZ }; // Used as template parameter
+enum TBType { WDL, DTZ }; // Used as template parameter
// Each table has a set of flags: all of them refer to DTZ tables, the last one to WDL tables
enum TBFlag { STM = 1, Mapped = 2, WinPlies = 4, LossPlies = 8, Wide = 16, SingleValue = 128 };
inline WDLScore operator-(WDLScore d) { return WDLScore(-int(d)); }
-inline Square operator^=(Square& s, int i) { return s = Square(int(s) ^ i); }
inline Square operator^(Square s, int i) { return Square(int(s) ^ i); }
-const std::string PieceToChar = " PNBRQK pnbrqk";
+constexpr std::string_view PieceToChar = " PNBRQK pnbrqk";
int MapPawns[SQUARE_NB];
int MapB1H1H7[SQUARE_NB];
template<typename T, int LE> T number(void* addr)
{
- static const union { uint32_t i; char c[4]; } Le = { 0x01020304 };
- static const bool IsLittleEndian = (Le.c[0] == 4);
-
T v;
if ((uintptr_t)addr & (alignof(T) - 1)) // Unaligned pointer (very rare)
static_assert(sizeof(SparseEntry) == 6, "SparseEntry must be 6 bytes");
-typedef uint16_t Sym; // Huffman symbol
+using Sym = uint16_t; // Huffman symbol
struct LR {
enum Side { Left, Right };
std::stringstream ss(Paths);
std::string path;
- while (std::getline(ss, path, SepChar)) {
+ while (std::getline(ss, path, SepChar))
+ {
fname = path + "/" + f;
std::ifstream::open(fname);
if (is_open())
}
}
- // Memory map the file and check it. File should be already open and will be
- // closed after mapping.
+ // Memory map the file and check it.
uint8_t* map(void** baseAddress, uint64_t* mapping, TBType type) {
-
- assert(is_open());
-
- close(); // Need to re-open to get native file descriptor
+ if (is_open())
+ close(); // Need to re-open to get native file descriptor
#ifndef _WIN32
struct stat statbuf;
return *baseAddress = nullptr, nullptr;
fstat(fd, &statbuf);
+
+ if (statbuf.st_size % 64 != 16)
+ {
+ std::cerr << "Corrupt tablebase file " << fname << std::endl;
+ exit(EXIT_FAILURE);
+ }
+
*mapping = statbuf.st_size;
*baseAddress = mmap(nullptr, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0);
+#if defined(MADV_RANDOM)
madvise(*baseAddress, statbuf.st_size, MADV_RANDOM);
+#endif
::close(fd);
- if (*baseAddress == MAP_FAILED) {
+ if (*baseAddress == MAP_FAILED)
+ {
std::cerr << "Could not mmap() " << fname << std::endl;
- exit(1);
+ exit(EXIT_FAILURE);
}
#else
+ // Note FILE_FLAG_RANDOM_ACCESS is only a hint to Windows and as such may get ignored.
HANDLE fd = CreateFile(fname.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr,
- OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+ OPEN_EXISTING, FILE_FLAG_RANDOM_ACCESS, nullptr);
if (fd == INVALID_HANDLE_VALUE)
return *baseAddress = nullptr, nullptr;
DWORD size_high;
DWORD size_low = GetFileSize(fd, &size_high);
+
+ if (size_low % 64 != 16)
+ {
+ std::cerr << "Corrupt tablebase file " << fname << std::endl;
+ exit(EXIT_FAILURE);
+ }
+
HANDLE mmap = CreateFileMapping(fd, nullptr, PAGE_READONLY, size_high, size_low, nullptr);
CloseHandle(fd);
- if (!mmap) {
+ if (!mmap)
+ {
std::cerr << "CreateFileMapping() failed" << std::endl;
- exit(1);
+ exit(EXIT_FAILURE);
}
*mapping = (uint64_t)mmap;
*baseAddress = MapViewOfFile(mmap, FILE_MAP_READ, 0, 0, 0);
- if (!*baseAddress) {
+ if (!*baseAddress)
+ {
std::cerr << "MapViewOfFile() failed, name = " << fname
<< ", error = " << GetLastError() << std::endl;
- exit(1);
+ exit(EXIT_FAILURE);
}
#endif
uint8_t* data = (uint8_t*)*baseAddress;
constexpr uint8_t Magics[][4] = { { 0xD7, 0x66, 0x0C, 0xA5 },
{ 0x71, 0xE8, 0x23, 0x5D } };
- if (memcmp(data, Magics[type == WDL], 4)) {
+ if (memcmp(data, Magics[type == WDL], 4))
+ {
std::cerr << "Corrupted table in file " << fname << std::endl;
unmap(*baseAddress, *mapping);
return *baseAddress = nullptr, nullptr;
// first access, when the corresponding file is memory mapped.
template<TBType Type>
struct TBTable {
- typedef typename std::conditional<Type == WDL, WDLScore, int>::type Ret;
+ using Ret = typename std::conditional<Type == WDL, WDLScore, int>::type;
static constexpr int Sides = Type == WDL ? 2 : 1;
hasPawns = pos.pieces(PAWN);
hasUniquePieces = false;
- for (Color c = WHITE; c <= BLACK; ++c)
+ for (Color c : { WHITE, BLACK })
for (PieceType pt = PAWN; pt < KING; ++pt)
if (popcount(pos.pieces(c, pt)) == 1)
hasUniquePieces = true;
// at init time, accessed at probe time.
class TBTables {
- typedef std::tuple<Key, TBTable<WDL>*, TBTable<DTZ>*> Entry;
+ struct Entry
+ {
+ Key key;
+ TBTable<WDL>* wdl;
+ TBTable<DTZ>* dtz;
+
+ template <TBType Type>
+ TBTable<Type>* get() const {
+ return (TBTable<Type>*)(Type == WDL ? (void*)wdl : (void*)dtz);
+ }
+ };
static constexpr int Size = 1 << 12; // 4K table, indexed by key's 12 lsb
static constexpr int Overflow = 1; // Number of elements allowed to map to the last bucket
void insert(Key key, TBTable<WDL>* wdl, TBTable<DTZ>* dtz) {
uint32_t homeBucket = (uint32_t)key & (Size - 1);
- Entry entry = std::make_tuple(key, wdl, dtz);
+ Entry entry{ key, wdl, dtz };
// Ensure last element is empty to avoid overflow when looking up
for (uint32_t bucket = homeBucket; bucket < Size + Overflow - 1; ++bucket) {
- Key otherKey = std::get<KEY>(hashTable[bucket]);
- if (otherKey == key || !std::get<WDL>(hashTable[bucket])) {
+ Key otherKey = hashTable[bucket].key;
+ if (otherKey == key || !hashTable[bucket].get<WDL>()) {
hashTable[bucket] = entry;
return;
}
// insert here and search for a new spot for the other element instead.
uint32_t otherHomeBucket = (uint32_t)otherKey & (Size - 1);
if (otherHomeBucket > homeBucket) {
- swap(entry, hashTable[bucket]);
+ std::swap(entry, hashTable[bucket]);
key = otherKey;
homeBucket = otherHomeBucket;
}
}
std::cerr << "TB hash table size too low!" << std::endl;
- exit(1);
+ exit(EXIT_FAILURE);
}
public:
template<TBType Type>
TBTable<Type>* get(Key key) {
for (const Entry* entry = &hashTable[(uint32_t)key & (Size - 1)]; ; ++entry) {
- if (std::get<KEY>(*entry) == key || !std::get<Type>(*entry))
- return std::get<Type>(*entry);
+ if (entry->key == key || !entry->get<Type>())
+ return entry->get<Type>();
}
}
// I(k) = k * d->span + d->span / 2 (1)
// First step is to get the 'k' of the I(k) nearest to our idx, using definition (1)
- uint32_t k = idx / d->span;
+ uint32_t k = uint32_t(idx / d->span);
// Then we read the corresponding SparseIndex[] entry
uint32_t block = number<uint32_t, LittleEndian>(&d->sparseIndex[k].block);
int buf64Size = 64;
Sym sym;
- while (true) {
+ while (true)
+ {
int len = 0; // This is the symbol length - d->min_sym_len
// Now get the symbol length. For any symbol s64 of length l right-padded
// All the symbols of a given length are consecutive integers (numerical
// sequence property), so we can compute the offset of our symbol of
// length len, stored at the beginning of buf64.
- sym = (buf64 - d->base64[len]) >> (64 - len - d->minSymLen);
+ sym = Sym((buf64 - d->base64[len]) >> (64 - len - d->minSymLen));
// Now add the value of the lowest symbol of length len to get our symbol
sym += number<Sym, LittleEndian>(&d->lowestSym[len]);
// We binary-search for our value recursively expanding into the left and
// right child symbols until we reach a leaf node where symlen[sym] + 1 == 1
// that will store the value we need.
- while (d->symlen[sym]) {
-
+ while (d->symlen[sym])
+ {
Sym left = d->btree[sym].get<LR::Left>();
// If a symbol contains 36 sub-symbols (d->symlen[sym] + 1 = 36) and
bool blackStronger = (pos.material_key() != entry->key);
int flipColor = (symmetricBlackToMove || blackStronger) * 8;
- int flipSquares = (symmetricBlackToMove || blackStronger) * 070;
+ int flipSquares = (symmetricBlackToMove || blackStronger) * 56;
int stm = (symmetricBlackToMove || blackStronger) ^ pos.side_to_move();
// For pawns, TB files store 4 separate tables according if leading pawn is on
leadPawns = b = pos.pieces(color_of(pc), PAWN);
do
- squares[size++] = pop_lsb(&b) ^ flipSquares;
+ squares[size++] = pop_lsb(b) ^ flipSquares;
while (b);
leadPawnsCnt = size;
std::swap(squares[0], *std::max_element(squares, squares + leadPawnsCnt, pawns_comp));
- tbFile = file_of(squares[0]);
- if (tbFile > FILE_D)
- tbFile = file_of(squares[0] ^ 7); // Horizontal flip: SQ_H1 -> SQ_A1
+ tbFile = File(edge_distance(file_of(squares[0])));
}
// DTZ tables are one-sided, i.e. they store positions only for white to
// directly map them to the correct color and square.
b = pos.pieces() ^ leadPawns;
do {
- Square s = pop_lsb(&b);
+ Square s = pop_lsb(b);
squares[size] = s ^ flipSquares;
pieces[size++] = Piece(pos.piece_on(s) ^ flipColor);
} while (b);
// Then we reorder the pieces to have the same sequence as the one stored
// in pieces[i]: the sequence that ensures the best compression.
- for (int i = leadPawnsCnt; i < size; ++i)
- for (int j = i; j < size; ++j)
+ for (int i = leadPawnsCnt; i < size - 1; ++i)
+ for (int j = i + 1; j < size; ++j)
if (d->pieces[i] == pieces[j])
{
std::swap(pieces[i], pieces[j]);
// the triangle A1-D1-D4.
if (file_of(squares[0]) > FILE_D)
for (int i = 0; i < size; ++i)
- squares[i] ^= 7; // Horizontal flip: SQ_H1 -> SQ_A1
+ squares[i] = flip_file(squares[i]);
// Encode leading pawns starting with the one with minimum MapPawns[] and
// proceeding in ascending order.
if (entry->hasPawns) {
idx = LeadPawnIdx[leadPawnsCnt][squares[0]];
- std::sort(squares + 1, squares + leadPawnsCnt, pawns_comp);
+ std::stable_sort(squares + 1, squares + leadPawnsCnt, pawns_comp);
for (int i = 1; i < leadPawnsCnt; ++i)
idx += Binomial[i][MapPawns[squares[i]]];
goto encode_remaining; // With pawns we have finished special treatments
}
- // In positions withouth pawns, we further flip the squares to ensure leading
+ // In positions without pawns, we further flip the squares to ensure leading
// piece is below RANK_5.
if (rank_of(squares[0]) > RANK_4)
for (int i = 0; i < size; ++i)
- squares[i] ^= 070; // Vertical flip: SQ_A8 -> SQ_A1
+ squares[i] = flip_rank(squares[i]);
// Look for the first piece of the leading group not on the A1-D4 diagonal
// and ensure it is mapped below the diagonal.
if (!off_A1H8(squares[i]))
continue;
- if (off_A1H8(squares[i]) > 0) // A1-H8 diagonal flip: SQ_A3 -> SQ_C3
+ if (off_A1H8(squares[i]) > 0) // A1-H8 diagonal flip: SQ_A3 -> SQ_C1
for (int j = i; j < size; ++j)
squares[j] = Square(((squares[j] >> 3) | (squares[j] << 3)) & 63);
break;
// Rs "together" in 62 * 61 / 2 ways (we divide by 2 because rooks can be
// swapped and still get the same position.)
//
- // In case we have at least 3 unique pieces (inlcuded kings) we encode them
+ // In case we have at least 3 unique pieces (included kings) we encode them
// together.
if (entry->hasUniquePieces) {
+ (squares[1] - adjust1)) * 62
+ squares[2] - adjust2;
- // First piece is on a1-h8 diagonal, second below: map this occurence to
+ // First piece is on a1-h8 diagonal, second below: map this occurrence to
// 6 to differentiate from the above case, rank_of() maps a1-d4 diagonal
// to 0...3 and finally MapB1H1H7[] maps the b1-h1-h7 triangle to 0..27.
else if (off_A1H8(squares[1]))
idx *= d->groupIdx[0];
Square* groupSq = squares + d->groupLen[0];
- // Encode remainig pawns then pieces according to square, in ascending order
+ // Encode remaining pawns then pieces according to square, in ascending order
bool remainingPawns = entry->hasPawns && entry->pawnCount[1];
while (d->groupLen[++next])
{
- std::sort(groupSq, groupSq + d->groupLen[next]);
+ std::stable_sort(groupSq, groupSq + d->groupLen[next]);
uint64_t n = 0;
// Map down a square if "comes later" than a square in the previous
// Group together pieces that will be encoded together. The general rule is that
// a group contains pieces of same type and color. The exception is the leading
-// group that, in case of positions withouth pawns, can be formed by 3 different
+// group that, in case of positions without pawns, can be formed by 3 different
// pieces (default) or by the king pair when there is not a unique piece apart
// from the kings. When there are pawns, pawns are always first in pieces[].
//
//
// This ensures unique encoding for the whole position. The order of the
// groups is a per-table parameter and could not follow the canonical leading
- // pawns/pieces -> remainig pawns -> remaining pieces. In particular the
+ // pawns/pieces -> remaining pawns -> remaining pieces. In particular the
// first group is at order[0] position and the remaining pawns, when present,
// are at order[1] position.
bool pp = e.hasPawns && e.pawnCount[1]; // Pawns on both sides
d->groupIdx[1] = idx;
idx *= Binomial[d->groupLen[1]][48 - d->groupLen[0]];
}
- else // Remainig pieces
+ else // Remaining pieces
{
d->groupIdx[next] = idx;
idx *= Binomial[d->groupLen[next]][freeSquares];
d->groupIdx[n] = idx;
}
-// In Recursive Pairing each symbol represents a pair of childern symbols. So
+// In Recursive Pairing each symbol represents a pair of children symbols. So
// read d->btree[] symbols data and expand each one in his left and right child
// symbol until reaching the leafs that represent the symbol value.
uint8_t set_symlen(PairsData* d, Sym s, std::vector<bool>& visited) {
d->sizeofBlock = 1ULL << *data++;
d->span = 1ULL << *data++;
- d->sparseIndexSize = (tbSize + d->span - 1) / d->span; // Round up
+ d->sparseIndexSize = size_t((tbSize + d->span - 1) / d->span); // Round up
auto padding = number<uint8_t, LittleEndian>(data++);
d->blocksNum = number<uint32_t, LittleEndian>(data); data += sizeof(uint32_t);
d->blockLengthSize = d->blocksNum + padding; // Padded to ensure SparseIndex[]
// so that d->lowestSym[i] >= d->lowestSym[i+1] (when read as LittleEndian).
// Starting from this we compute a base64[] table indexed by symbol length
// and containing 64 bit values so that d->base64[i] >= d->base64[i+1].
- // See http://www.eecs.harvard.edu/~michaelm/E210/huffman.pdf
+ // See https://en.wikipedia.org/wiki/Huffman_coding
for (int i = d->base64.size() - 2; i >= 0; --i) {
d->base64[i] = (d->base64[i + 1] + number<Sym, LittleEndian>(&d->lowestSym[i])
- number<Sym, LittleEndian>(&d->lowestSym[i + 1])) / 2;
enum { Split = 1, HasPawns = 2 };
- assert(e.hasPawns == !!(*data & HasPawns));
- assert((e.key != e.key2) == !!(*data & Split));
+ assert(e.hasPawns == bool(*data & HasPawns));
+ assert((e.key != e.key2) == bool(*data & Split));
data++; // First byte stores flags
template<TBType Type>
void* mapped(TBTable<Type>& e, const Position& pos) {
- static Mutex mutex;
+ static std::mutex mutex;
- // Use 'aquire' to avoid a thread reads 'ready' == true while another is
- // still working, this could happen due to compiler reordering.
+ // Use 'acquire' to avoid a thread reading 'ready' == true while
+ // another is still working. (compiler reordering may cause this).
if (e.ready.load(std::memory_order_acquire))
- return e.baseAddress; // Could be nullptr if file does not exsist
+ return e.baseAddress; // Could be nullptr if file does not exist
- std::unique_lock<Mutex> lk(mutex);
+ std::scoped_lock<std::mutex> lk(mutex);
if (e.ready.load(std::memory_order_relaxed)) // Recheck under lock
return e.baseAddress;
auto moveList = MoveList<LEGAL>(pos);
size_t totalCount = moveList.size(), moveCount = 0;
- for (const Move& move : moveList)
+ for (const Move move : moveList)
{
if ( !pos.capture(move)
&& (!CheckZeroingMoves || type_of(pos.moved_piece(move)) != PAWN))
for (auto s : diagonal)
MapA1D1D4[s] = code++;
- // MapKK[] encodes all the 461 possible legal positions of two kings where
+ // MapKK[] encodes all the 462 possible legal positions of two kings where
// the first is in the a1-d1-d4 triangle. If the first king is on the a1-d4
// diagonal, the other one shall not to be above the a1-h8 diagonal.
std::vector<std::pair<int, Square>> bothOnDiagonal;
for (auto p : bothOnDiagonal)
MapKK[p.first][p.second] = code++;
- // Binomial[] stores the Binomial Coefficents using Pascal rule. There
+ // Binomial[] stores the Binomial Coefficients using Pascal rule. There
// are Binomial[k][n] ways to choose k elements from a set of n elements.
Binomial[0][0] = 1;
for (int leadPawnsCnt = 1; leadPawnsCnt <= 5; ++leadPawnsCnt)
for (File f = FILE_A; f <= FILE_D; ++f)
{
- // Restart the index at every file because TB table is splitted
+ // Restart the index at every file because TB table is split
// by file, so we can reuse the same index for different files.
int idx = 0;
if (leadPawnsCnt == 1)
{
MapPawns[sq] = availableSquares--;
- MapPawns[sq ^ 7] = availableSquares--; // Horizontal flip
+ MapPawns[flip_file(sq)] = availableSquares--;
}
LeadPawnIdx[leadPawnsCnt][sq] = idx;
idx += Binomial[leadPawnsCnt - 1][MapPawns[sq]];
LeadPawnsSize[leadPawnsCnt][f] = idx;
}
- // Add entries in TB tables if the corresponding ".rtbw" file exsists
+ // Add entries in TB tables if the corresponding ".rtbw" file exists
for (PieceType p1 = PAWN; p1 < KING; ++p1) {
TBTables.add({KING, p1, KING});
// If n = 100 immediately after a capture or pawn move, then the position
// is also certainly a win, and during the whole phase until the next
// capture or pawn move, the inequality to be preserved is
-// dtz + 50-movecounter <= 100.
+// dtz + 50-move-counter <= 100.
//
// In short, if a move is available resulting in dtz + 50-move-counter <= 99,
// then do not accept moves leading to dtz + 50-move-counter == 100.
StateInfo st;
int minDTZ = 0xFFFF;
- for (const Move& move : MoveList<LEGAL>(pos))
+ for (const Move move : MoveList<LEGAL>(pos))
{
bool zeroing = pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN;
// A return value false indicates that not all probes were successful.
bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
- ProbeState result;
+ ProbeState result = OK;
StateInfo st;
// Obtain 50-move counter for the root position
// Check whether a position was repeated since the last zeroing move.
bool rep = pos.has_repeated();
- int dtz, bound = Options["Syzygy50MoveRule"] ? 900 : 1;
+ int dtz, bound = Options["Syzygy50MoveRule"] ? (MAX_DTZ - 100) : 1;
// Probe and rank each move
for (auto& m : rootMoves)
WDLScore wdl = -probe_wdl(pos, &result);
dtz = dtz_before_zeroing(wdl);
}
+ else if (pos.is_draw(1))
+ {
+ // In case a root move leads to a draw by repetition or
+ // 50-move rule, we set dtz to zero. Note: since we are
+ // only 1 ply from the root, this must be a true 3-fold
+ // repetition inside the game history.
+ dtz = 0;
+ }
else
{
// Otherwise, take dtz for the new position and correct by 1 ply
// Better moves are ranked higher. Certain wins are ranked equally.
// Losing moves are ranked equally unless a 50-move draw is in sight.
- int r = dtz > 0 ? (dtz + cnt50 <= 99 && !rep ? 1000 : 1000 - (dtz + cnt50))
- : dtz < 0 ? (-dtz * 2 + cnt50 < 100 ? -1000 : -1000 + (-dtz + cnt50))
+ int r = dtz > 0 ? (dtz + cnt50 <= 99 && !rep ? MAX_DTZ : MAX_DTZ - (dtz + cnt50))
+ : dtz < 0 ? (-dtz * 2 + cnt50 < 100 ? -MAX_DTZ : -MAX_DTZ + (-dtz + cnt50))
: 0;
m.tbRank = r;
// 1 cp to cursed wins and let it grow to 49 cp as the positions gets
// closer to a real win.
m.tbScore = r >= bound ? VALUE_MATE - MAX_PLY - 1
- : r > 0 ? Value((std::max( 3, r - 800) * int(PawnValueEg)) / 200)
+ : r > 0 ? Value((std::max( 3, r - (MAX_DTZ - 200)) * int(PawnValueEg)) / 200)
: r == 0 ? VALUE_DRAW
- : r > -bound ? Value((std::min(-3, r + 800) * int(PawnValueEg)) / 200)
+ : r > -bound ? Value((std::min(-3, r + (MAX_DTZ - 200)) * int(PawnValueEg)) / 200)
: -VALUE_MATE + MAX_PLY + 1;
}
// A return value false indicates that not all probes were successful.
bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves) {
- static const int WDL_to_rank[] = { -1000, -899, 0, 899, 1000 };
+ static const int WDL_to_rank[] = { -MAX_DTZ, -MAX_DTZ + 101, 0, MAX_DTZ - 101, MAX_DTZ };
- ProbeState result;
+ ProbeState result = OK;
StateInfo st;
+ WDLScore wdl;
bool rule50 = Options["Syzygy50MoveRule"];
{
pos.do_move(m.pv[0], st);
- WDLScore wdl = -probe_wdl(pos, &result);
+ if (pos.is_draw(1))
+ wdl = WDLDraw;
+ else
+ wdl = -probe_wdl(pos, &result);
pos.undo_move(m.pv[0]);
return true;
}
+
+} // namespace Stockfish