X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsyzygy%2Ftbprobe.cpp;h=c0cd04c1d4d8bd8f30607b616ae02363cb84da69;hp=646176a9e7a6468eb76e03d35c2465d6041904cf;hb=699bae632f283746a3eee15c0950fcdbca8a355e;hpb=0da7295795448fc826cb5b2613ac64a6e0c4adcd diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp index 646176a9..c0cd04c1 100644 --- a/src/syzygy/tbprobe.cpp +++ b/src/syzygy/tbprobe.cpp @@ -1,569 +1,1431 @@ /* - Copyright (c) 2013 Ronald de Man - This file may be redistributed and/or modified without restrictions. + Stockfish, a UCI chess playing engine derived from Glaurung 2.1 + Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file) - tbprobe.cpp contains the Stockfish-specific routines of the - tablebase probing code. It should be relatively easy to adapt - this code to other chess engines. -*/ + 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. -#define NOMINMAX + You should have received a copy of the GNU General Public License + along with this program. If not, see . +*/ #include +#include +#include +#include // For std::memset and std::memcpy +#include +#include +#include +#include +#include +#include +#include -#include "../position.h" -#include "../movegen.h" #include "../bitboard.h" +#include "../movegen.h" +#include "../position.h" #include "../search.h" -#include "../bitcount.h" +#include "../types.h" +#include "../uci.h" #include "tbprobe.h" -#include "tbcore.h" -#include "tbcore.cpp" +#ifndef _WIN32 +#include +#include +#include +#include +#else +#define WIN32_LEAN_AND_MEAN +#ifndef NOMINMAX +# define NOMINMAX // Disable macros min() and max() +#endif +#include +#endif + +using namespace Stockfish::Tablebases; -namespace Zobrist { - extern Key psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB]; -} +int Stockfish::Tablebases::MaxCardinality; -int Tablebases::MaxCardinality = 0; +namespace Stockfish { -// Given a position with 6 or fewer pieces, produce a text string -// of the form KQPvKRP, where "KQP" represents the white pieces if -// mirror == 0 and the black pieces if mirror == 1. -static void prt_str(Position& pos, char *str, int mirror) -{ - Color color; - PieceType pt; - int i; - - color = !mirror ? WHITE : BLACK; - for (pt = KING; pt >= PAWN; --pt) - for (i = popcount(pos.pieces(color, pt)); i > 0; i--) - *str++ = pchr[6 - pt]; - *str++ = 'v'; - color = ~color; - for (pt = KING; pt >= PAWN; --pt) - for (i = popcount(pos.pieces(color, pt)); i > 0; i--) - *str++ = pchr[6 - pt]; - *str++ = 0; -} +namespace { + +constexpr int TBPIECES = 7; // Max number of supported pieces + +enum { BigEndian, LittleEndian }; +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 Square(int(s) ^ i); } + +const std::string PieceToChar = " PNBRQK pnbrqk"; + +int MapPawns[SQUARE_NB]; +int MapB1H1H7[SQUARE_NB]; +int MapA1D1D4[SQUARE_NB]; +int MapKK[10][SQUARE_NB]; // [MapA1D1D4][SQUARE_NB] -// Given a position, produce a 64-bit material signature key. -// If the engine supports such a key, it should equal the engine's key. -static uint64 calc_key(Position& pos, int mirror) +int Binomial[7][SQUARE_NB]; // [k][n] k elements from a set of n elements +int LeadPawnIdx[6][SQUARE_NB]; // [leadPawnsCnt][SQUARE_NB] +int LeadPawnsSize[6][4]; // [leadPawnsCnt][FILE_A..FILE_D] + +// Comparison function to sort leading pawns in ascending MapPawns[] order +bool pawns_comp(Square i, Square j) { return MapPawns[i] < MapPawns[j]; } +int off_A1H8(Square sq) { return int(rank_of(sq)) - file_of(sq); } + +constexpr Value WDL_to_value[] = { + -VALUE_MATE + MAX_PLY + 1, + VALUE_DRAW - 2, + VALUE_DRAW, + VALUE_DRAW + 2, + VALUE_MATE - MAX_PLY - 1 +}; + +template +inline void swap_endian(T& x) { - Color color; - PieceType pt; - int i; - uint64 key = 0; - - color = !mirror ? WHITE : BLACK; - for (pt = PAWN; pt <= KING; ++pt) - for (i = popcount(pos.pieces(color, pt)); i > 0; i--) - key ^= Zobrist::psq[WHITE][pt][i - 1]; - color = ~color; - for (pt = PAWN; pt <= KING; ++pt) - for (i = popcount(pos.pieces(color, pt)); i > 0; i--) - key ^= Zobrist::psq[BLACK][pt][i - 1]; - - return key; + static_assert(std::is_unsigned::value, "Argument of swap_endian not unsigned"); + + uint8_t tmp, *c = (uint8_t*)&x; + for (int i = 0; i < Half; ++i) + tmp = c[i], c[i] = c[End - i], c[End - i] = tmp; } +template<> inline void swap_endian(uint8_t&) {} -// Produce a 64-bit material key corresponding to the material combination -// defined by pcs[16], where pcs[1], ..., pcs[6] is the number of white -// pawns, ..., kings and pcs[9], ..., pcs[14] is the number of black -// pawns, ..., kings. -static uint64 calc_key_from_pcs(int *pcs, int mirror) +template T number(void* addr) { - int color; - PieceType pt; - int i; - uint64 key = 0; - - color = !mirror ? 0 : 8; - for (pt = PAWN; pt <= KING; ++pt) - for (i = 0; i < pcs[color + pt]; i++) - key ^= Zobrist::psq[WHITE][pt][i]; - color ^= 8; - for (pt = PAWN; pt <= KING; ++pt) - for (i = 0; i < pcs[color + pt]; i++) - key ^= Zobrist::psq[BLACK][pt][i]; - - return key; + 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) + std::memcpy(&v, addr, sizeof(T)); + else + v = *((T*)addr); + + if (LE != IsLittleEndian) + swap_endian(v); + return v; } -bool is_little_endian() { - union { - int i; - char c[sizeof(int)]; - } x; - x.i = 1; - return x.c[0] == 1; +// DTZ tables don't store valid scores for moves that reset the rule50 counter +// like captures and pawn moves but we can easily recover the correct dtz of the +// previous move if we know the position's WDL score. +int dtz_before_zeroing(WDLScore wdl) { + return wdl == WDLWin ? 1 : + wdl == WDLCursedWin ? 101 : + wdl == WDLBlessedLoss ? -101 : + wdl == WDLLoss ? -1 : 0; } -static ubyte decompress_pairs(struct PairsData *d, uint64 idx) -{ - static const bool isLittleEndian = is_little_endian(); - return isLittleEndian ? decompress_pairs(d, idx) - : decompress_pairs(d, idx); +// Return the sign of a number (-1, 0, 1) +template int sign_of(T val) { + return (T(0) < val) - (val < T(0)); } -// probe_wdl_table and probe_dtz_table require similar adaptations. -static int probe_wdl_table(Position& pos, int *success) -{ - struct TBEntry *ptr; - struct TBHashEntry *ptr2; - uint64 idx; - uint64 key; - int i; - ubyte res; - int p[TBPIECES]; - - // Obtain the position's material signature key. - key = pos.material_key(); - - // Test for KvK. - if (key == (Zobrist::psq[WHITE][KING][0] ^ Zobrist::psq[BLACK][KING][0])) - return 0; - - ptr2 = TB_hash[key >> (64 - TBHASHBITS)]; - for (i = 0; i < HSHMAX; i++) - if (ptr2[i].key == key) break; - if (i == HSHMAX) { - *success = 0; - return 0; - } - - ptr = ptr2[i].ptr; - if (!ptr->ready) { - LOCK(TB_mutex); - if (!ptr->ready) { - char str[16]; - prt_str(pos, str, ptr->key != key); - if (!init_table_wdl(ptr, str)) { - ptr2[i].key = 0ULL; - *success = 0; - UNLOCK(TB_mutex); - return 0; - } - // Memory barrier to ensure ptr->ready = 1 is not reordered. -#ifdef _MSC_VER - _ReadWriteBarrier(); +// Numbers in little endian used by sparseIndex[] to point into blockLength[] +struct SparseEntry { + char block[4]; // Number of block + char offset[2]; // Offset within the block +}; + +static_assert(sizeof(SparseEntry) == 6, "SparseEntry must be 6 bytes"); + +typedef uint16_t Sym; // Huffman symbol + +struct LR { + enum Side { Left, Right }; + + uint8_t lr[3]; // The first 12 bits is the left-hand symbol, the second 12 + // bits is the right-hand symbol. If symbol has length 1, + // then the left-hand symbol is the stored value. + template + Sym get() { + return S == Left ? ((lr[1] & 0xF) << 8) | lr[0] : + S == Right ? (lr[2] << 4) | (lr[1] >> 4) : (assert(false), Sym(-1)); + } +}; + +static_assert(sizeof(LR) == 3, "LR tree entry must be 3 bytes"); + +// Tablebases data layout is structured as following: +// +// TBFile: memory maps/unmaps the physical .rtbw and .rtbz files +// TBTable: one object for each file with corresponding indexing information +// TBTables: has ownership of TBTable objects, keeping a list and a hash + +// class TBFile memory maps/unmaps the single .rtbw and .rtbz files. Files are +// memory mapped for best performance. Files are mapped at first access: at init +// time only existence of the file is checked. +class TBFile : public std::ifstream { + + std::string fname; + +public: + // Look for and open the file among the Paths directories where the .rtbw + // and .rtbz files can be found. Multiple directories are separated by ";" + // on Windows and by ":" on Unix-based operating systems. + // + // Example: + // C:\tb\wdl345;C:\tb\wdl6;D:\tb\dtz345;D:\tb\dtz6 + static std::string Paths; + + TBFile(const std::string& f) { + +#ifndef _WIN32 + constexpr char SepChar = ':'; #else - __asm__ __volatile__ ("" ::: "memory"); + constexpr char SepChar = ';'; #endif - ptr->ready = 1; + std::stringstream ss(Paths); + std::string path; + + while (std::getline(ss, path, SepChar)) { + fname = path + "/" + f; + std::ifstream::open(fname); + if (is_open()) + return; + } } - UNLOCK(TB_mutex); - } - - int bside, mirror, cmirror; - if (!ptr->symmetric) { - if (key != ptr->key) { - cmirror = 8; - mirror = 0x38; - bside = (pos.side_to_move() == WHITE); - } else { - cmirror = mirror = 0; - bside = !(pos.side_to_move() == WHITE); + + // Memory map the file and check it. File should be already open and will be + // closed after mapping. + uint8_t* map(void** baseAddress, uint64_t* mapping, TBType type) { + + assert(is_open()); + + close(); // Need to re-open to get native file descriptor + +#ifndef _WIN32 + struct stat statbuf; + int fd = ::open(fname.c_str(), O_RDONLY); + + if (fd == -1) + 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) + { + std::cerr << "Could not mmap() " << fname << std::endl; + 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_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) + { + std::cerr << "CreateFileMapping() failed" << std::endl; + exit(EXIT_FAILURE); + } + + *mapping = (uint64_t)mmap; + *baseAddress = MapViewOfFile(mmap, FILE_MAP_READ, 0, 0, 0); + + if (!*baseAddress) + { + std::cerr << "MapViewOfFile() failed, name = " << fname + << ", error = " << GetLastError() << std::endl; + 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)) + { + std::cerr << "Corrupted table in file " << fname << std::endl; + unmap(*baseAddress, *mapping); + return *baseAddress = nullptr, nullptr; + } + + return data + 4; // Skip Magics's header } - } else { - cmirror = pos.side_to_move() == WHITE ? 0 : 8; - mirror = pos.side_to_move() == WHITE ? 0 : 0x38; - bside = 0; - } - - // p[i] is to contain the square 0-63 (A1-H8) for a piece of type - // pc[i] ^ cmirror, where 1 = white pawn, ..., 14 = black king. - // Pieces of the same type are guaranteed to be consecutive. - if (!ptr->has_pawns) { - struct TBEntry_piece *entry = (struct TBEntry_piece *)ptr; - ubyte *pc = entry->pieces[bside]; - for (i = 0; i < entry->num;) { - Bitboard bb = pos.pieces((Color)((pc[i] ^ cmirror) >> 3), - (PieceType)(pc[i] & 0x07)); - do { - p[i++] = pop_lsb(&bb); - } while (bb); + + static void unmap(void* baseAddress, uint64_t mapping) { + +#ifndef _WIN32 + munmap(baseAddress, mapping); +#else + UnmapViewOfFile(baseAddress); + CloseHandle((HANDLE)mapping); +#endif } - idx = encode_piece(entry, entry->norm[bside], p, entry->factor[bside]); - res = decompress_pairs(entry->precomp[bside], idx); - } else { - struct TBEntry_pawn *entry = (struct TBEntry_pawn *)ptr; - int k = entry->file[0].pieces[0][0] ^ cmirror; - Bitboard bb = pos.pieces((Color)(k >> 3), (PieceType)(k & 0x07)); - i = 0; - do { - p[i++] = pop_lsb(&bb) ^ mirror; - } while (bb); - int f = pawn_file(entry, p); - ubyte *pc = entry->file[f].pieces[bside]; - for (; i < entry->num;) { - bb = pos.pieces((Color)((pc[i] ^ cmirror) >> 3), - (PieceType)(pc[i] & 0x07)); - do { - p[i++] = pop_lsb(&bb) ^ mirror; - } while (bb); +}; + +std::string TBFile::Paths; + +// struct PairsData contains low level indexing information to access TB data. +// There are 8, 4 or 2 PairsData records for each TBTable, according to type of +// table and if positions have pawns or not. It is populated at first access. +struct PairsData { + uint8_t flags; // Table flags, see enum TBFlag + uint8_t maxSymLen; // Maximum length in bits of the Huffman symbols + uint8_t minSymLen; // Minimum length in bits of the Huffman symbols + uint32_t blocksNum; // Number of blocks in the TB file + size_t sizeofBlock; // Block size in bytes + size_t span; // About every span values there is a SparseIndex[] entry + Sym* lowestSym; // lowestSym[l] is the symbol of length l with the lowest value + LR* btree; // btree[sym] stores the left and right symbols that expand sym + uint16_t* blockLength; // Number of stored positions (minus one) for each block: 1..65536 + uint32_t blockLengthSize; // Size of blockLength[] table: padded so it's bigger than blocksNum + SparseEntry* sparseIndex; // Partial indices into blockLength[] + size_t sparseIndexSize; // Size of SparseIndex[] table + uint8_t* data; // Start of Huffman compressed data + std::vector base64; // base64[l - min_sym_len] is the 64bit-padded lowest symbol of length l + std::vector symlen; // Number of values (-1) represented by a given Huffman symbol: 1..256 + Piece pieces[TBPIECES]; // Position pieces: the order of pieces defines the groups + uint64_t groupIdx[TBPIECES+1]; // Start index used for the encoding of the group's pieces + int groupLen[TBPIECES+1]; // Number of pieces in a given group: KRKN -> (3, 1) + uint16_t map_idx[4]; // WDLWin, WDLLoss, WDLCursedWin, WDLBlessedLoss (used in DTZ) +}; + +// struct TBTable contains indexing information to access the corresponding TBFile. +// There are 2 types of TBTable, corresponding to a WDL or a DTZ file. TBTable +// is populated at init time but the nested PairsData records are populated at +// first access, when the corresponding file is memory mapped. +template +struct TBTable { + typedef typename std::conditional::type Ret; + + static constexpr int Sides = Type == WDL ? 2 : 1; + + std::atomic_bool ready; + void* baseAddress; + uint8_t* map; + uint64_t mapping; + Key key; + Key key2; + int pieceCount; + bool hasPawns; + bool hasUniquePieces; + uint8_t pawnCount[2]; // [Lead color / other color] + PairsData items[Sides][4]; // [wtm / btm][FILE_A..FILE_D or 0] + + PairsData* get(int stm, int f) { + return &items[stm % Sides][hasPawns ? f : 0]; + } + + TBTable() : ready(false), baseAddress(nullptr) {} + explicit TBTable(const std::string& code); + explicit TBTable(const TBTable& wdl); + + ~TBTable() { + if (baseAddress) + TBFile::unmap(baseAddress, mapping); } - idx = encode_pawn(entry, entry->file[f].norm[bside], p, entry->file[f].factor[bside]); - res = decompress_pairs(entry->file[f].precomp[bside], idx); - } +}; + +template<> +TBTable::TBTable(const std::string& code) : TBTable() { + + StateInfo st; + Position pos; - return ((int)res) - 2; + key = pos.set(code, WHITE, &st).material_key(); + pieceCount = pos.count(); + hasPawns = pos.pieces(PAWN); + + hasUniquePieces = false; + for (Color c : { WHITE, BLACK }) + for (PieceType pt = PAWN; pt < KING; ++pt) + if (popcount(pos.pieces(c, pt)) == 1) + hasUniquePieces = true; + + // Set the leading color. In case both sides have pawns the leading color + // is the side with less pawns because this leads to better compression. + bool c = !pos.count(BLACK) + || ( pos.count(WHITE) + && pos.count(BLACK) >= pos.count(WHITE)); + + pawnCount[0] = pos.count(c ? WHITE : BLACK); + pawnCount[1] = pos.count(c ? BLACK : WHITE); + + key2 = pos.set(code, BLACK, &st).material_key(); } -static int probe_dtz_table(Position& pos, int wdl, int *success) -{ - struct TBEntry *ptr; - uint64 idx; - int i, res; - int p[TBPIECES]; - - // Obtain the position's material signature key. - uint64 key = pos.material_key(); - - if (DTZ_table[0].key1 != key && DTZ_table[0].key2 != key) { - for (i = 1; i < DTZ_ENTRIES; i++) - if (DTZ_table[i].key1 == key) break; - if (i < DTZ_ENTRIES) { - struct DTZTableEntry table_entry = DTZ_table[i]; - for (; i > 0; i--) - DTZ_table[i] = DTZ_table[i - 1]; - DTZ_table[0] = table_entry; - } else { - struct TBHashEntry *ptr2 = TB_hash[key >> (64 - TBHASHBITS)]; - for (i = 0; i < HSHMAX; i++) - if (ptr2[i].key == key) break; - if (i == HSHMAX) { - *success = 0; - return 0; - } - ptr = ptr2[i].ptr; - char str[16]; - int mirror = (ptr->key != key); - prt_str(pos, str, mirror); - if (DTZ_table[DTZ_ENTRIES - 1].entry) - free_dtz_entry(DTZ_table[DTZ_ENTRIES-1].entry); - for (i = DTZ_ENTRIES - 1; i > 0; i--) - DTZ_table[i] = DTZ_table[i - 1]; - load_dtz_table(str, calc_key(pos, mirror), calc_key(pos, !mirror)); +template<> +TBTable::TBTable(const TBTable& wdl) : TBTable() { + + // Use the corresponding WDL table to avoid recalculating all from scratch + key = wdl.key; + key2 = wdl.key2; + pieceCount = wdl.pieceCount; + hasPawns = wdl.hasPawns; + hasUniquePieces = wdl.hasUniquePieces; + pawnCount[0] = wdl.pawnCount[0]; + pawnCount[1] = wdl.pawnCount[1]; +} + +// class TBTables creates and keeps ownership of the TBTable objects, one for +// each TB file found. It supports a fast, hash based, table lookup. Populated +// at init time, accessed at probe time. +class TBTables { + + struct Entry + { + Key key; + TBTable* wdl; + TBTable* dtz; + + template + TBTable* get() const { + return (TBTable*)(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 + + Entry hashTable[Size + Overflow]; + + std::deque> wdlTable; + std::deque> dtzTable; + + void insert(Key key, TBTable* wdl, TBTable* dtz) { + uint32_t homeBucket = (uint32_t)key & (Size - 1); + 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 = hashTable[bucket].key; + if (otherKey == key || !hashTable[bucket].get()) { + hashTable[bucket] = entry; + return; + } + + // Robin Hood hashing: If we've probed for longer than this element, + // insert here and search for a new spot for the other element instead. + uint32_t otherHomeBucket = (uint32_t)otherKey & (Size - 1); + if (otherHomeBucket > homeBucket) { + std::swap(entry, hashTable[bucket]); + key = otherKey; + homeBucket = otherHomeBucket; + } + } + std::cerr << "TB hash table size too low!" << std::endl; + exit(EXIT_FAILURE); + } + +public: + template + TBTable* get(Key key) { + for (const Entry* entry = &hashTable[(uint32_t)key & (Size - 1)]; ; ++entry) { + if (entry->key == key || !entry->get()) + return entry->get(); + } + } + + void clear() { + memset(hashTable, 0, sizeof(hashTable)); + wdlTable.clear(); + dtzTable.clear(); + } + size_t size() const { return wdlTable.size(); } + void add(const std::vector& pieces); +}; + +TBTables TBTables; + +// If the corresponding file exists two new objects TBTable and TBTable +// are created and added to the lists and hash table. Called at init time. +void TBTables::add(const std::vector& pieces) { + + std::string code; + + for (PieceType pt : pieces) + code += PieceToChar[pt]; + + TBFile file(code.insert(code.find('K', 1), "v") + ".rtbw"); // KRK -> KRvK + + if (!file.is_open()) // Only WDL file is checked + return; + + file.close(); + + MaxCardinality = std::max((int)pieces.size(), MaxCardinality); + + wdlTable.emplace_back(code); + dtzTable.emplace_back(wdlTable.back()); + + // Insert into the hash keys for both colors: KRvK with KR white and black + insert(wdlTable.back().key , &wdlTable.back(), &dtzTable.back()); + insert(wdlTable.back().key2, &wdlTable.back(), &dtzTable.back()); +} + +// TB tables are compressed with canonical Huffman code. The compressed data is divided into +// blocks of size d->sizeofBlock, and each block stores a variable number of symbols. +// Each symbol represents either a WDL or a (remapped) DTZ value, or a pair of other symbols +// (recursively). If you keep expanding the symbols in a block, you end up with up to 65536 +// WDL or DTZ values. Each symbol represents up to 256 values and will correspond after +// Huffman coding to at least 1 bit. So a block of 32 bytes corresponds to at most +// 32 x 8 x 256 = 65536 values. This maximum is only reached for tables that consist mostly +// of draws or mostly of wins, but such tables are actually quite common. In principle, the +// blocks in WDL tables are 64 bytes long (and will be aligned on cache lines). But for +// mostly-draw or mostly-win tables this can leave many 64-byte blocks only half-filled, so +// in such cases blocks are 32 bytes long. The blocks of DTZ tables are up to 1024 bytes long. +// The generator picks the size that leads to the smallest table. The "book" of symbols and +// Huffman codes is the same for all blocks in the table. A non-symmetric pawnless TB file +// will have one table for wtm and one for btm, a TB file with pawns will have tables per +// file a,b,c,d also in this case one set for wtm and one for btm. +int decompress_pairs(PairsData* d, uint64_t idx) { + + // Special case where all table positions store the same value + if (d->flags & TBFlag::SingleValue) + return d->minSymLen; + + // First we need to locate the right block that stores the value at index "idx". + // Because each block n stores blockLength[n] + 1 values, the index i of the block + // that contains the value at position idx is: + // + // for (i = -1, sum = 0; sum <= idx; i++) + // sum += blockLength[i + 1] + 1; + // + // This can be slow, so we use SparseIndex[] populated with a set of SparseEntry that + // point to known indices into blockLength[]. Namely SparseIndex[k] is a SparseEntry + // that stores the blockLength[] index and the offset within that block of the value + // with index I(k), where: + // + // 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 = uint32_t(idx / d->span); + + // Then we read the corresponding SparseIndex[] entry + uint32_t block = number(&d->sparseIndex[k].block); + int offset = number(&d->sparseIndex[k].offset); + + // Now compute the difference idx - I(k). From definition of k we know that + // + // idx = k * d->span + idx % d->span (2) + // + // So from (1) and (2) we can compute idx - I(K): + int diff = idx % d->span - d->span / 2; + + // Sum the above to offset to find the offset corresponding to our idx + offset += diff; + + // Move to previous/next block, until we reach the correct block that contains idx, + // that is when 0 <= offset <= d->blockLength[block] + while (offset < 0) + offset += d->blockLength[--block] + 1; + + while (offset > d->blockLength[block]) + offset -= d->blockLength[block++] + 1; + + // Finally, we find the start address of our block of canonical Huffman symbols + uint32_t* ptr = (uint32_t*)(d->data + ((uint64_t)block * d->sizeofBlock)); + + // Read the first 64 bits in our block, this is a (truncated) sequence of + // unknown number of symbols of unknown length but we know the first one + // is at the beginning of this 64 bits sequence. + uint64_t buf64 = number(ptr); ptr += 2; + int buf64Size = 64; + Sym sym; + + 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 + // to 64 bits we know that d->base64[l-1] >= s64 >= d->base64[l] so we + // can find the symbol length iterating through base64[]. + while (buf64 < d->base64[len]) + ++len; + + // 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 = 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(&d->lowestSym[len]); + + // If our offset is within the number of values represented by symbol sym + // we are done... + if (offset < d->symlen[sym] + 1) + break; + + // ...otherwise update the offset and continue to iterate + offset -= d->symlen[sym] + 1; + len += d->minSymLen; // Get the real length + buf64 <<= len; // Consume the just processed symbol + buf64Size -= len; + + if (buf64Size <= 32) { // Refill the buffer + buf64Size += 32; + buf64 |= (uint64_t)number(ptr++) << (64 - buf64Size); + } } - } - - ptr = DTZ_table[0].entry; - if (!ptr) { - *success = 0; - return 0; - } - - int bside, mirror, cmirror; - if (!ptr->symmetric) { - if (key != ptr->key) { - cmirror = 8; - mirror = 0x38; - bside = (pos.side_to_move() == WHITE); - } else { - cmirror = mirror = 0; - bside = !(pos.side_to_move() == WHITE); + + // Ok, now we have our symbol that expands into d->symlen[sym] + 1 symbols. + // 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]) { + + Sym left = d->btree[sym].get(); + + // If a symbol contains 36 sub-symbols (d->symlen[sym] + 1 = 36) and + // expands in a pair (d->symlen[left] = 23, d->symlen[right] = 11), then + // we know that, for instance the ten-th value (offset = 10) will be on + // the left side because in Recursive Pairing child symbols are adjacent. + if (offset < d->symlen[left] + 1) + sym = left; + else { + offset -= d->symlen[left] + 1; + sym = d->btree[sym].get(); + } } - } else { - cmirror = pos.side_to_move() == WHITE ? 0 : 8; - mirror = pos.side_to_move() == WHITE ? 0 : 0x38; - bside = 0; - } - - if (!ptr->has_pawns) { - struct DTZEntry_piece *entry = (struct DTZEntry_piece *)ptr; - if ((entry->flags & 1) != bside && !entry->symmetric) { - *success = -1; - return 0; + + return d->btree[sym].get(); +} + +bool check_dtz_stm(TBTable*, int, File) { return true; } + +bool check_dtz_stm(TBTable* entry, int stm, File f) { + + auto flags = entry->get(stm, f)->flags; + return (flags & TBFlag::STM) == stm + || ((entry->key == entry->key2) && !entry->hasPawns); +} + +// DTZ scores are sorted by frequency of occurrence and then assigned the +// values 0, 1, 2, ... in order of decreasing frequency. This is done for each +// of the four WDLScore values. The mapping information necessary to reconstruct +// the original values is stored in the TB file and read during map[] init. +WDLScore map_score(TBTable*, File, int value, WDLScore) { return WDLScore(value - 2); } + +int map_score(TBTable* entry, File f, int value, WDLScore wdl) { + + constexpr int WDLMap[] = { 1, 3, 0, 2, 0 }; + + auto flags = entry->get(0, f)->flags; + + uint8_t* map = entry->map; + uint16_t* idx = entry->get(0, f)->map_idx; + if (flags & TBFlag::Mapped) { + if (flags & TBFlag::Wide) + value = ((uint16_t *)map)[idx[WDLMap[wdl + 2]] + value]; + else + value = map[idx[WDLMap[wdl + 2]] + value]; } - ubyte *pc = entry->pieces; - for (i = 0; i < entry->num;) { - Bitboard bb = pos.pieces((Color)((pc[i] ^ cmirror) >> 3), - (PieceType)(pc[i] & 0x07)); - do { - p[i++] = pop_lsb(&bb); - } while (bb); + + // DTZ tables store distance to zero in number of moves or plies. We + // want to return plies, so we have convert to plies when needed. + if ( (wdl == WDLWin && !(flags & TBFlag::WinPlies)) + || (wdl == WDLLoss && !(flags & TBFlag::LossPlies)) + || wdl == WDLCursedWin + || wdl == WDLBlessedLoss) + value *= 2; + + return value + 1; +} + +// Compute a unique index out of a position and use it to probe the TB file. To +// encode k pieces of same type and color, first sort the pieces by square in +// ascending order s1 <= s2 <= ... <= sk then compute the unique index as: +// +// idx = Binomial[1][s1] + Binomial[2][s2] + ... + Binomial[k][sk] +// +template +Ret do_probe_table(const Position& pos, T* entry, WDLScore wdl, ProbeState* result) { + + Square squares[TBPIECES]; + Piece pieces[TBPIECES]; + uint64_t idx; + int next = 0, size = 0, leadPawnsCnt = 0; + PairsData* d; + Bitboard b, leadPawns = 0; + File tbFile = FILE_A; + + // A given TB entry like KRK has associated two material keys: KRvk and Kvkr. + // If both sides have the same pieces keys are equal. In this case TB tables + // only store the 'white to move' case, so if the position to lookup has black + // to move, we need to switch the color and flip the squares before to lookup. + bool symmetricBlackToMove = (entry->key == entry->key2 && pos.side_to_move()); + + // TB files are calculated for white as stronger side. For instance we have + // KRvK, not KvKR. A position where stronger side is white will have its + // material key == entry->key, otherwise we have to switch the color and + // flip the squares before to lookup. + bool blackStronger = (pos.material_key() != entry->key); + + int flipColor = (symmetricBlackToMove || blackStronger) * 8; + 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 + // file a, b, c or d after reordering. The leading pawn is the one with maximum + // MapPawns[] value, that is the one most toward the edges and with lowest rank. + if (entry->hasPawns) { + + // In all the 4 tables, pawns are at the beginning of the piece sequence and + // their color is the reference one. So we just pick the first one. + Piece pc = Piece(entry->get(0, 0)->pieces[0] ^ flipColor); + + assert(type_of(pc) == PAWN); + + leadPawns = b = pos.pieces(color_of(pc), PAWN); + do + squares[size++] = pop_lsb(&b) ^ flipSquares; + while (b); + + leadPawnsCnt = size; + + std::swap(squares[0], *std::max_element(squares, squares + leadPawnsCnt, pawns_comp)); + + tbFile = File(edge_distance(file_of(squares[0]))); } - idx = encode_piece((struct TBEntry_piece *)entry, entry->norm, p, entry->factor); - res = decompress_pairs(entry->precomp, idx); - - if (entry->flags & 2) - res = entry->map[entry->map_idx[wdl_to_map[wdl + 2]] + res]; - - if (!(entry->flags & pa_flags[wdl + 2]) || (wdl & 1)) - res *= 2; - } else { - struct DTZEntry_pawn *entry = (struct DTZEntry_pawn *)ptr; - int k = entry->file[0].pieces[0] ^ cmirror; - Bitboard bb = pos.pieces((Color)(k >> 3), (PieceType)(k & 0x07)); - i = 0; + + // DTZ tables are one-sided, i.e. they store positions only for white to + // move or only for black to move, so check for side to move to be stm, + // early exit otherwise. + if (!check_dtz_stm(entry, stm, tbFile)) + return *result = CHANGE_STM, Ret(); + + // Now we are ready to get all the position pieces (but the lead pawns) and + // directly map them to the correct color and square. + b = pos.pieces() ^ leadPawns; do { - p[i++] = pop_lsb(&bb) ^ mirror; - } while (bb); - int f = pawn_file((struct TBEntry_pawn *)entry, p); - if ((entry->flags[f] & 1) != bside) { - *success = -1; - return 0; + Square s = pop_lsb(&b); + squares[size] = s ^ flipSquares; + pieces[size++] = Piece(pos.piece_on(s) ^ flipColor); + } while (b); + + assert(size >= 2); + + d = entry->get(stm, tbFile); + + // 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 - 1; ++i) + for (int j = i + 1; j < size; ++j) + if (d->pieces[i] == pieces[j]) + { + std::swap(pieces[i], pieces[j]); + std::swap(squares[i], squares[j]); + break; + } + + // Now we map again the squares so that the square of the lead piece is in + // the triangle A1-D1-D4. + if (file_of(squares[0]) > FILE_D) + for (int i = 0; i < size; ++i) + 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::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 } - ubyte *pc = entry->file[f].pieces; - for (; i < entry->num;) { - bb = pos.pieces((Color)((pc[i] ^ cmirror) >> 3), - (PieceType)(pc[i] & 0x07)); - do { - p[i++] = pop_lsb(&bb) ^ mirror; - } while (bb); + + // In positions withouth 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] = 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. + for (int i = 0; i < d->groupLen[0]; ++i) { + if (!off_A1H8(squares[i])) + continue; + + 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; } - idx = encode_pawn((struct TBEntry_pawn *)entry, entry->file[f].norm, p, entry->file[f].factor); - res = decompress_pairs(entry->file[f].precomp, idx); - if (entry->flags[f] & 2) - res = entry->map[entry->map_idx[f][wdl_to_map[wdl + 2]] + res]; + // Encode the leading group. + // + // Suppose we have KRvK. Let's say the pieces are on square numbers wK, wR + // and bK (each 0...63). The simplest way to map this position to an index + // is like this: + // + // index = wK * 64 * 64 + wR * 64 + bK; + // + // But this way the TB is going to have 64*64*64 = 262144 positions, with + // lots of positions being equivalent (because they are mirrors of each + // other) and lots of positions being invalid (two pieces on one square, + // adjacent kings, etc.). + // Usually the first step is to take the wK and bK together. There are just + // 462 ways legal and not-mirrored ways to place the wK and bK on the board. + // Once we have placed the wK and bK, there are 62 squares left for the wR + // Mapping its square from 0..63 to available squares 0..61 can be done like: + // + // wR -= (wR > wK) + (wR > bK); + // + // In words: if wR "comes later" than wK, we deduct 1, and the same if wR + // "comes later" than bK. In case of two same pieces like KRRvK we want to + // place the two Rs "together". If we have 62 squares left, we can place two + // 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 + // together. + if (entry->hasUniquePieces) { + + int adjust1 = squares[1] > squares[0]; + int adjust2 = (squares[2] > squares[0]) + (squares[2] > squares[1]); + + // First piece is below a1-h8 diagonal. MapA1D1D4[] maps the b1-d1-d3 + // triangle to 0...5. There are 63 squares for second piece and and 62 + // (mapped to 0...61) for the third. + if (off_A1H8(squares[0])) + idx = ( MapA1D1D4[squares[0]] * 63 + + (squares[1] - adjust1)) * 62 + + squares[2] - adjust2; + + // First piece is on a1-h8 diagonal, second below: map this occurence 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 = ( 6 * 63 + rank_of(squares[0]) * 28 + + MapB1H1H7[squares[1]]) * 62 + + squares[2] - adjust2; + + // First two pieces are on a1-h8 diagonal, third below + else if (off_A1H8(squares[2])) + idx = 6 * 63 * 62 + 4 * 28 * 62 + + rank_of(squares[0]) * 7 * 28 + + (rank_of(squares[1]) - adjust1) * 28 + + MapB1H1H7[squares[2]]; + + // All 3 pieces on the diagonal a1-h8 + else + idx = 6 * 63 * 62 + 4 * 28 * 62 + 4 * 7 * 28 + + rank_of(squares[0]) * 7 * 6 + + (rank_of(squares[1]) - adjust1) * 6 + + (rank_of(squares[2]) - adjust2); + } else + // We don't have at least 3 unique pieces, like in KRRvKBB, just map + // the kings. + idx = MapKK[MapA1D1D4[squares[0]]][squares[1]]; + +encode_remaining: + idx *= d->groupIdx[0]; + Square* groupSq = squares + d->groupLen[0]; + + // Encode remainig pawns then pieces according to square, in ascending order + bool remainingPawns = entry->hasPawns && entry->pawnCount[1]; + + while (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 + // groups (similar to what done earlier for leading group pieces). + for (int i = 0; i < d->groupLen[next]; ++i) + { + auto f = [&](Square s) { return groupSq[i] > s; }; + auto adjust = std::count_if(squares, groupSq, f); + n += Binomial[i + 1][groupSq[i] - adjust - 8 * remainingPawns]; + } - if (!(entry->flags[f] & pa_flags[wdl + 2]) || (wdl & 1)) - res *= 2; - } + remainingPawns = false; + idx += n * d->groupIdx[next]; + groupSq += d->groupLen[next]; + } - return res; + // Now that we have the index, decompress the pair and get the score + return map_score(entry, tbFile, decompress_pairs(d, idx), wdl); } -// Add underpromotion captures to list of captures. -static ExtMove *add_underprom_caps(Position& pos, ExtMove *stack, ExtMove *end) -{ - ExtMove *moves, *extra = end; - - for (moves = stack; moves < end; moves++) { - Move move = moves->move; - if (type_of(move) == PROMOTION && !pos.empty(to_sq(move))) { - (*extra++).move = (Move)(move - (1 << 12)); - (*extra++).move = (Move)(move - (2 << 12)); - (*extra++).move = (Move)(move - (3 << 12)); +// 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 +// 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[]. +// +// As example KRKN -> KRK + N, KNNK -> KK + NN, KPPKP -> P + PP + K + K +// +// The actual grouping depends on the TB generator and can be inferred from the +// sequence of pieces in piece[] array. +template +void set_groups(T& e, PairsData* d, int order[], File f) { + + int n = 0, firstLen = e.hasPawns ? 0 : e.hasUniquePieces ? 3 : 2; + d->groupLen[n] = 1; + + // Number of pieces per group is stored in groupLen[], for instance in KRKN + // the encoder will default on '111', so groupLen[] will be (3, 1). + for (int i = 1; i < e.pieceCount; ++i) + if (--firstLen > 0 || d->pieces[i] == d->pieces[i - 1]) + d->groupLen[n]++; + else + d->groupLen[++n] = 1; + + d->groupLen[++n] = 0; // Zero-terminated + + // The sequence in pieces[] defines the groups, but not the order in which + // they are encoded. If the pieces in a group g can be combined on the board + // in N(g) different ways, then the position encoding will be of the form: + // + // g1 * N(g2) * N(g3) + g2 * N(g3) + g3 + // + // 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 + // 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 + int next = pp ? 2 : 1; + int freeSquares = 64 - d->groupLen[0] - (pp ? d->groupLen[1] : 0); + uint64_t idx = 1; + + for (int k = 0; next < n || k == order[0] || k == order[1]; ++k) + if (k == order[0]) // Leading pawns or pieces + { + d->groupIdx[0] = idx; + idx *= e.hasPawns ? LeadPawnsSize[d->groupLen[0]][f] + : e.hasUniquePieces ? 31332 : 462; + } + else if (k == order[1]) // Remaining pawns + { + d->groupIdx[1] = idx; + idx *= Binomial[d->groupLen[1]][48 - d->groupLen[0]]; + } + else // Remainig pieces + { + d->groupIdx[next] = idx; + idx *= Binomial[d->groupLen[next]][freeSquares]; + freeSquares -= d->groupLen[next++]; + } + + d->groupIdx[n] = idx; +} + +// In Recursive Pairing each symbol represents a pair of childern 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& visited) { + + visited[s] = true; // We can set it now because tree is acyclic + Sym sr = d->btree[s].get(); + + if (sr == 0xFFF) + return 0; + + Sym sl = d->btree[s].get(); + + if (!visited[sl]) + d->symlen[sl] = set_symlen(d, sl, visited); + + if (!visited[sr]) + d->symlen[sr] = set_symlen(d, sr, visited); + + return d->symlen[sl] + d->symlen[sr] + 1; +} + +uint8_t* set_sizes(PairsData* d, uint8_t* data) { + + d->flags = *data++; + + if (d->flags & TBFlag::SingleValue) { + d->blocksNum = d->blockLengthSize = 0; + d->span = d->sparseIndexSize = 0; // Broken MSVC zero-init + d->minSymLen = *data++; // Here we store the single value + return data; + } + + // groupLen[] is a zero-terminated list of group lengths, the last groupIdx[] + // element stores the biggest index that is the tb size. + uint64_t tbSize = d->groupIdx[std::find(d->groupLen, d->groupLen + 7, 0) - d->groupLen]; + + d->sizeofBlock = 1ULL << *data++; + d->span = 1ULL << *data++; + d->sparseIndexSize = size_t((tbSize + d->span - 1) / d->span); // Round up + auto padding = number(data++); + d->blocksNum = number(data); data += sizeof(uint32_t); + d->blockLengthSize = d->blocksNum + padding; // Padded to ensure SparseIndex[] + // does not point out of range. + d->maxSymLen = *data++; + d->minSymLen = *data++; + d->lowestSym = (Sym*)data; + d->base64.resize(d->maxSymLen - d->minSymLen + 1); + + // The canonical code is ordered such that longer symbols (in terms of + // the number of bits of their Huffman code) have lower numeric value, + // 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 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(&d->lowestSym[i]) + - number(&d->lowestSym[i + 1])) / 2; + + assert(d->base64[i] * 2 >= d->base64[i+1]); } - } - return extra; + // Now left-shift by an amount so that d->base64[i] gets shifted 1 bit more + // than d->base64[i+1] and given the above assert condition, we ensure that + // d->base64[i] >= d->base64[i+1]. Moreover for any symbol s64 of length i + // and right-padded to 64 bits holds d->base64[i-1] >= s64 >= d->base64[i]. + for (size_t i = 0; i < d->base64.size(); ++i) + d->base64[i] <<= 64 - i - d->minSymLen; // Right-padding to 64 bits + + data += d->base64.size() * sizeof(Sym); + d->symlen.resize(number(data)); data += sizeof(uint16_t); + d->btree = (LR*)data; + + // The compression scheme used is "Recursive Pairing", that replaces the most + // frequent adjacent pair of symbols in the source message by a new symbol, + // reevaluating the frequencies of all of the symbol pairs with respect to + // the extended alphabet, and then repeating the process. + // See http://www.larsson.dogma.net/dcc99.pdf + std::vector visited(d->symlen.size()); + + for (Sym sym = 0; sym < d->symlen.size(); ++sym) + if (!visited[sym]) + d->symlen[sym] = set_symlen(d, sym, visited); + + return data + d->symlen.size() * sizeof(LR) + (d->symlen.size() & 1); } -static int probe_ab(Position& pos, int alpha, int beta, int *success) -{ - int v; - ExtMove stack[64]; - ExtMove *moves, *end; - StateInfo st; - - // Generate (at least) all legal non-ep captures including (under)promotions. - // It is OK to generate more, as long as they are filtered out below. - if (!pos.checkers()) { - end = generate(pos, stack); - // Since underpromotion captures are not included, we need to add them. - end = add_underprom_caps(pos, stack, end); - } else - end = generate(pos, stack); - - CheckInfo ci(pos); - - for (moves = stack; moves < end; moves++) { - Move capture = moves->move; - if (!pos.capture(capture) || type_of(capture) == ENPASSANT - || !pos.legal(capture, ci.pinned)) - continue; - pos.do_move(capture, st, pos.gives_check(capture, ci)); - v = -probe_ab(pos, -beta, -alpha, success); - pos.undo_move(capture); - if (*success == 0) return 0; - if (v > alpha) { - if (v >= beta) { - *success = 2; - return v; - } - alpha = v; +uint8_t* set_dtz_map(TBTable&, uint8_t* data, File) { return data; } + +uint8_t* set_dtz_map(TBTable& e, uint8_t* data, File maxFile) { + + e.map = data; + + for (File f = FILE_A; f <= maxFile; ++f) { + auto flags = e.get(0, f)->flags; + if (flags & TBFlag::Mapped) { + if (flags & TBFlag::Wide) { + data += (uintptr_t)data & 1; // Word alignment, we may have a mixed table + for (int i = 0; i < 4; ++i) { // Sequence like 3,x,x,x,1,x,0,2,x,x + e.get(0, f)->map_idx[i] = (uint16_t)((uint16_t *)data - (uint16_t *)e.map + 1); + data += 2 * number(data) + 2; + } + } + else { + for (int i = 0; i < 4; ++i) { + e.get(0, f)->map_idx[i] = (uint16_t)(data - e.map + 1); + data += *data + 1; + } + } + } } - } - - v = probe_wdl_table(pos, success); - if (*success == 0) return 0; - if (alpha >= v) { - *success = 1 + (alpha > 0); - return alpha; - } else { - *success = 1; - return v; - } + + return data += (uintptr_t)data & 1; // Word alignment } -// Probe the WDL table for a particular position. -// If *success != 0, the probe was successful. -// The return value is from the point of view of the side to move: -// -2 : loss -// -1 : loss, but draw under 50-move rule -// 0 : draw -// 1 : win, but draw under 50-move rule -// 2 : win -int Tablebases::probe_wdl(Position& pos, int *success) -{ - int v; +// Populate entry's PairsData records with data from the just memory mapped file. +// Called at first access. +template +void set(T& e, uint8_t* data) { - *success = 1; - v = probe_ab(pos, -2, 2, success); + PairsData* d; - // If en passant is not possible, we are done. - if (pos.ep_square() == SQ_NONE) - return v; - if (!(*success)) return 0; - - // Now handle en passant. - int v1 = -3; - // Generate (at least) all legal en passant captures. - ExtMove stack[192]; - ExtMove *moves, *end; - StateInfo st; - - if (!pos.checkers()) - end = generate(pos, stack); - else - end = generate(pos, stack); - - CheckInfo ci(pos); - - for (moves = stack; moves < end; moves++) { - Move capture = moves->move; - if (type_of(capture) != ENPASSANT - || !pos.legal(capture, ci.pinned)) - continue; - pos.do_move(capture, st, pos.gives_check(capture, ci)); - int v0 = -probe_ab(pos, -2, 2, success); - pos.undo_move(capture); - if (*success == 0) return 0; - if (v0 > v1) v1 = v0; - } - if (v1 > -3) { - if (v1 >= v) v = v1; - else if (v == 0) { - // Check whether there is at least one legal non-ep move. - for (moves = stack; moves < end; moves++) { - Move capture = moves->move; - if (type_of(capture) == ENPASSANT) continue; - if (pos.legal(capture, ci.pinned)) break; - } - if (moves == end && !pos.checkers()) { - end = generate(pos, end); - for (; moves < end; moves++) { - Move move = moves->move; - if (pos.legal(move, ci.pinned)) - break; - } - } - // If not, then we are forced to play the losing ep capture. - if (moves == end) - v = v1; + enum { Split = 1, HasPawns = 2 }; + + assert(e.hasPawns == bool(*data & HasPawns)); + assert((e.key != e.key2) == bool(*data & Split)); + + data++; // First byte stores flags + + const int sides = T::Sides == 2 && (e.key != e.key2) ? 2 : 1; + const File maxFile = e.hasPawns ? FILE_D : FILE_A; + + bool pp = e.hasPawns && e.pawnCount[1]; // Pawns on both sides + + assert(!pp || e.pawnCount[0]); + + for (File f = FILE_A; f <= maxFile; ++f) { + + for (int i = 0; i < sides; i++) + *e.get(i, f) = PairsData(); + + int order[][2] = { { *data & 0xF, pp ? *(data + 1) & 0xF : 0xF }, + { *data >> 4, pp ? *(data + 1) >> 4 : 0xF } }; + data += 1 + pp; + + for (int k = 0; k < e.pieceCount; ++k, ++data) + for (int i = 0; i < sides; i++) + e.get(i, f)->pieces[k] = Piece(i ? *data >> 4 : *data & 0xF); + + for (int i = 0; i < sides; ++i) + set_groups(e, e.get(i, f), order[i], f); } - } - return v; + data += (uintptr_t)data & 1; // Word alignment + + for (File f = FILE_A; f <= maxFile; ++f) + for (int i = 0; i < sides; i++) + data = set_sizes(e.get(i, f), data); + + data = set_dtz_map(e, data, maxFile); + + for (File f = FILE_A; f <= maxFile; ++f) + for (int i = 0; i < sides; i++) { + (d = e.get(i, f))->sparseIndex = (SparseEntry*)data; + data += d->sparseIndexSize * sizeof(SparseEntry); + } + + for (File f = FILE_A; f <= maxFile; ++f) + for (int i = 0; i < sides; i++) { + (d = e.get(i, f))->blockLength = (uint16_t*)data; + data += d->blockLengthSize * sizeof(uint16_t); + } + + for (File f = FILE_A; f <= maxFile; ++f) + for (int i = 0; i < sides; i++) { + data = (uint8_t*)(((uintptr_t)data + 0x3F) & ~0x3F); // 64 byte alignment + (d = e.get(i, f))->data = data; + data += d->blocksNum * d->sizeofBlock; + } } -// This routine treats a position with en passant captures as one without. -static int probe_dtz_no_ep(Position& pos, int *success) -{ - int wdl, dtz; +// If the TB file corresponding to the given position is already memory mapped +// then return its base address, otherwise try to memory map and init it. Called +// at every probe, memory map and init only at first access. Function is thread +// safe and can be called concurrently. +template +void* mapped(TBTable& e, const Position& pos) { - wdl = probe_ab(pos, -2, 2, success); - if (*success == 0) return 0; + static std::mutex mutex; - if (wdl == 0) return 0; + // 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 exist - if (*success == 2) - return wdl == 2 ? 1 : 101; + std::scoped_lock lk(mutex); - ExtMove stack[192]; - ExtMove *moves, *end = NULL; - StateInfo st; - CheckInfo ci(pos); + if (e.ready.load(std::memory_order_relaxed)) // Recheck under lock + return e.baseAddress; - if (wdl > 0) { - // Generate at least all legal non-capturing pawn moves - // including non-capturing promotions. - if (!pos.checkers()) - end = generate(pos, stack); - else - end = generate(pos, stack); - - for (moves = stack; moves < end; moves++) { - Move move = moves->move; - if (type_of(pos.moved_piece(move)) != PAWN || pos.capture(move) - || !pos.legal(move, ci.pinned)) - continue; - pos.do_move(move, st, pos.gives_check(move, ci)); - int v = -probe_ab(pos, -2, -wdl + 1, success); - pos.undo_move(move); - if (*success == 0) return 0; - if (v == wdl) - return v == 2 ? 1 : 101; + // Pieces strings in decreasing order for each color, like ("KPP","KR") + std::string fname, w, b; + for (PieceType pt = KING; pt >= PAWN; --pt) { + w += std::string(popcount(pos.pieces(WHITE, pt)), PieceToChar[pt]); + b += std::string(popcount(pos.pieces(BLACK, pt)), PieceToChar[pt]); } - } - - dtz = 1 + probe_dtz_table(pos, wdl, success); - if (*success >= 0) { - if (wdl & 1) dtz += 100; - return wdl >= 0 ? dtz : -dtz; - } - - if (wdl > 0) { - int best = 0xffff; - for (moves = stack; moves < end; moves++) { - Move move = moves->move; - if (pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN - || !pos.legal(move, ci.pinned)) - continue; - pos.do_move(move, st, pos.gives_check(move, ci)); - int v = -Tablebases::probe_dtz(pos, success); - pos.undo_move(move); - if (*success == 0) return 0; - if (v > 0 && v + 1 < best) - best = v + 1; + + fname = (e.key == pos.material_key() ? w + 'v' + b : b + 'v' + w) + + (Type == WDL ? ".rtbw" : ".rtbz"); + + uint8_t* data = TBFile(fname).map(&e.baseAddress, &e.mapping, Type); + + if (data) + set(e, data); + + e.ready.store(true, std::memory_order_release); + return e.baseAddress; +} + +template::Ret> +Ret probe_table(const Position& pos, ProbeState* result, WDLScore wdl = WDLDraw) { + + if (pos.count() == 2) // KvK + return Ret(WDLDraw); + + TBTable* entry = TBTables.get(pos.material_key()); + + if (!entry || !mapped(*entry, pos)) + return *result = FAIL, Ret(); + + return do_probe_table(pos, entry, wdl, result); +} + +// For a position where the side to move has a winning capture it is not necessary +// to store a winning value so the generator treats such positions as "don't cares" +// and tries to assign to it a value that improves the compression ratio. Similarly, +// if the side to move has a drawing capture, then the position is at least drawn. +// If the position is won, then the TB needs to store a win value. But if the +// position is drawn, the TB may store a loss value if that is better for compression. +// All of this means that during probing, the engine must look at captures and probe +// their results and must probe the position itself. The "best" result of these +// probes is the correct result for the position. +// DTZ tables do not store values when a following move is a zeroing winning move +// (winning capture or winning pawn move). Also DTZ store wrong values for positions +// where the best move is an ep-move (even if losing). So in all these cases set +// the state to ZEROING_BEST_MOVE. +template +WDLScore search(Position& pos, ProbeState* result) { + + WDLScore value, bestValue = WDLLoss; + StateInfo st; + + auto moveList = MoveList(pos); + size_t totalCount = moveList.size(), moveCount = 0; + + for (const Move move : moveList) + { + if ( !pos.capture(move) + && (!CheckZeroingMoves || type_of(pos.moved_piece(move)) != PAWN)) + continue; + + moveCount++; + + pos.do_move(move, st); + value = -search(pos, result); + pos.undo_move(move); + + if (*result == FAIL) + return WDLDraw; + + if (value > bestValue) + { + bestValue = value; + + if (value >= WDLWin) + { + *result = ZEROING_BEST_MOVE; // Winning DTZ-zeroing move + return value; + } + } } - return best; - } else { - int best = -1; - if (!pos.checkers()) - end = generate(pos, stack); + + // In case we have already searched all the legal moves we don't have to probe + // the TB because the stored score could be wrong. For instance TB tables + // do not contain information on position with ep rights, so in this case + // the result of probe_wdl_table is wrong. Also in case of only capture + // moves, for instance here 4K3/4q3/6p1/2k5/6p1/8/8/8 w - - 0 7, we have to + // return with ZEROING_BEST_MOVE set. + bool noMoreMoves = (moveCount && moveCount == totalCount); + + if (noMoreMoves) + value = bestValue; else - end = generate(pos, stack); - for (moves = stack; moves < end; moves++) { - int v; - Move move = moves->move; - if (!pos.legal(move, ci.pinned)) - continue; - pos.do_move(move, st, pos.gives_check(move, ci)); - if (st.rule50 == 0) { - if (wdl == -2) v = -1; - else { - v = probe_ab(pos, 1, 2, success); - v = (v == 2) ? 0 : -101; + { + value = probe_table(pos, result); + + if (*result == FAIL) + return WDLDraw; + } + + // DTZ stores a "don't care" value if bestValue is a win + if (bestValue >= value) + return *result = ( bestValue > WDLDraw + || noMoreMoves ? ZEROING_BEST_MOVE : OK), bestValue; + + return *result = OK, value; +} + +} // namespace + + +/// Tablebases::init() is called at startup and after every change to +/// "SyzygyPath" UCI option to (re)create the various tables. It is not thread +/// safe, nor it needs to be. +void Tablebases::init(const std::string& paths) { + + TBTables.clear(); + MaxCardinality = 0; + TBFile::Paths = paths; + + if (paths.empty() || paths == "") + return; + + // MapB1H1H7[] encodes a square below a1-h8 diagonal to 0..27 + int code = 0; + for (Square s = SQ_A1; s <= SQ_H8; ++s) + if (off_A1H8(s) < 0) + MapB1H1H7[s] = code++; + + // MapA1D1D4[] encodes a square in the a1-d1-d4 triangle to 0..9 + std::vector diagonal; + code = 0; + for (Square s = SQ_A1; s <= SQ_D4; ++s) + if (off_A1H8(s) < 0 && file_of(s) <= FILE_D) + MapA1D1D4[s] = code++; + + else if (!off_A1H8(s) && file_of(s) <= FILE_D) + diagonal.push_back(s); + + // Diagonal squares are encoded as last ones + for (auto s : diagonal) + MapA1D1D4[s] = code++; + + // MapKK[] encodes all the 461 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> bothOnDiagonal; + code = 0; + for (int idx = 0; idx < 10; idx++) + for (Square s1 = SQ_A1; s1 <= SQ_D4; ++s1) + if (MapA1D1D4[s1] == idx && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0 + { + for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2) + if ((PseudoAttacks[KING][s1] | s1) & s2) + continue; // Illegal position + + else if (!off_A1H8(s1) && off_A1H8(s2) > 0) + continue; // First on diagonal, second above + + else if (!off_A1H8(s1) && !off_A1H8(s2)) + bothOnDiagonal.emplace_back(idx, s2); + + else + MapKK[idx][s2] = code++; + } + + // Legal positions with both kings on diagonal are encoded as last ones + for (auto p : bothOnDiagonal) + MapKK[p.first][p.second] = code++; + + // Binomial[] stores the Binomial Coefficents 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 n = 1; n < 64; n++) // Squares + for (int k = 0; k < 7 && k <= n; ++k) // Pieces + Binomial[k][n] = (k > 0 ? Binomial[k - 1][n - 1] : 0) + + (k < n ? Binomial[k ][n - 1] : 0); + + // MapPawns[s] encodes squares a2-h7 to 0..47. This is the number of possible + // available squares when the leading one is in 's'. Moreover the pawn with + // highest MapPawns[] is the leading pawn, the one nearest the edge and, + // among pawns with same file, the one with lowest rank. + int availableSquares = 47; // Available squares when lead pawn is in a2 + + // Init the tables for the encoding of leading pawns group: with 7-men TB we + // can have up to 5 leading pawns (KPPPPPK). + 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 + // by file, so we can reuse the same index for different files. + int idx = 0; + + // Sum all possible combinations for a given file, starting with + // the leading pawn on rank 2 and increasing the rank. + for (Rank r = RANK_2; r <= RANK_7; ++r) + { + Square sq = make_square(f, r); + + // Compute MapPawns[] at first pass. + // If sq is the leading pawn square, any other pawn cannot be + // below or more toward the edge of sq. There are 47 available + // squares when sq = a2 and reduced by 2 for any rank increase + // due to mirroring: sq == a3 -> no a2, h2, so MapPawns[a3] = 45 + if (leadPawnsCnt == 1) + { + MapPawns[sq] = availableSquares--; + MapPawns[flip_file(sq)] = availableSquares--; + } + LeadPawnIdx[leadPawnsCnt][sq] = idx; + idx += Binomial[leadPawnsCnt - 1][MapPawns[sq]]; + } + // After a file is traversed, store the cumulated per-file index + LeadPawnsSize[leadPawnsCnt][f] = idx; + } + + // Add entries in TB tables if the corresponding ".rtbw" file exists + for (PieceType p1 = PAWN; p1 < KING; ++p1) { + TBTables.add({KING, p1, KING}); + + for (PieceType p2 = PAWN; p2 <= p1; ++p2) { + TBTables.add({KING, p1, p2, KING}); + TBTables.add({KING, p1, KING, p2}); + + for (PieceType p3 = PAWN; p3 < KING; ++p3) + TBTables.add({KING, p1, p2, KING, p3}); + + for (PieceType p3 = PAWN; p3 <= p2; ++p3) { + TBTables.add({KING, p1, p2, p3, KING}); + + for (PieceType p4 = PAWN; p4 <= p3; ++p4) { + TBTables.add({KING, p1, p2, p3, p4, KING}); + + for (PieceType p5 = PAWN; p5 <= p4; ++p5) + TBTables.add({KING, p1, p2, p3, p4, p5, KING}); + + for (PieceType p5 = PAWN; p5 < KING; ++p5) + TBTables.add({KING, p1, p2, p3, p4, KING, p5}); + } + + for (PieceType p4 = PAWN; p4 < KING; ++p4) { + TBTables.add({KING, p1, p2, p3, KING, p4}); + + for (PieceType p5 = PAWN; p5 <= p4; ++p5) + TBTables.add({KING, p1, p2, p3, KING, p4, p5}); + } + } + + for (PieceType p3 = PAWN; p3 <= p1; ++p3) + for (PieceType p4 = PAWN; p4 <= (p1 == p3 ? p2 : p3); ++p4) + TBTables.add({KING, p1, p2, KING, p3, p4}); } - } else { - v = -Tablebases::probe_dtz(pos, success) - 1; - } - pos.undo_move(move); - if (*success == 0) return 0; - if (v < best) - best = v; } - return best; - } + + sync_cout << "info string Found " << TBTables.size() << " tablebases" << sync_endl; } -static int wdl_to_dtz[] = { - -1, -101, 0, 101, 1 -}; +// Probe the WDL table for a particular position. +// If *result != FAIL, the probe was successful. +// The return value is from the point of view of the side to move: +// -2 : loss +// -1 : loss, but draw under 50-move rule +// 0 : draw +// 1 : win, but draw under 50-move rule +// 2 : win +WDLScore Tablebases::probe_wdl(Position& pos, ProbeState* result) { + + *result = OK; + return search(pos, result); +} // Probe the DTZ table for a particular position. -// If *success != 0, the probe was successful. +// If *result != FAIL, the probe was successful. // The return value is from the point of view of the side to move: // n < -100 : loss, but draw under 50-move rule // -100 <= n < -1 : loss in n ply (assuming 50-move counter == 0) +// -1 : loss, the side to move is mated // 0 : draw // 1 < n <= 100 : win in n ply (assuming 50-move counter == 0) // 100 < n : win, but draw under 50-move rule @@ -580,254 +1442,175 @@ static int wdl_to_dtz[] = { // 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. -// -int Tablebases::probe_dtz(Position& pos, int *success) -{ - *success = 1; - int v = probe_dtz_no_ep(pos, success); +int Tablebases::probe_dtz(Position& pos, ProbeState* result) { - if (pos.ep_square() == SQ_NONE) - return v; - if (*success == 0) return 0; - - // Now handle en passant. - int v1 = -3; - - ExtMove stack[192]; - ExtMove *moves, *end; - StateInfo st; - - if (!pos.checkers()) - end = generate(pos, stack); - else - end = generate(pos, stack); - CheckInfo ci(pos); - - for (moves = stack; moves < end; moves++) { - Move capture = moves->move; - if (type_of(capture) != ENPASSANT - || !pos.legal(capture, ci.pinned)) - continue; - pos.do_move(capture, st, pos.gives_check(capture, ci)); - int v0 = -probe_ab(pos, -2, 2, success); - pos.undo_move(capture); - if (*success == 0) return 0; - if (v0 > v1) v1 = v0; - } - if (v1 > -3) { - v1 = wdl_to_dtz[v1 + 2]; - if (v < -100) { - if (v1 >= 0) - v = v1; - } else if (v < 0) { - if (v1 >= 0 || v1 < 100) - v = v1; - } else if (v > 100) { - if (v1 > 0) - v = v1; - } else if (v > 0) { - if (v1 == 1) - v = v1; - } else if (v1 >= 0) { - v = v1; - } else { - for (moves = stack; moves < end; moves++) { - Move move = moves->move; - if (type_of(move) == ENPASSANT) continue; - if (pos.legal(move, ci.pinned)) break; - } - if (moves == end && !pos.checkers()) { - end = generate(pos, end); - for (; moves < end; moves++) { - Move move = moves->move; - if (pos.legal(move, ci.pinned)) - break; - } - } - if (moves == end) - v = v1; - } - } + *result = OK; + WDLScore wdl = search(pos, result); - return v; -} + if (*result == FAIL || wdl == WDLDraw) // DTZ tables don't store draws + return 0; -// Check whether there has been at least one repetition of positions -// since the last capture or pawn move. -static int has_repeated(StateInfo *st) -{ - while (1) { - int i = 4, e = std::min(st->rule50, st->pliesFromNull); - if (e < i) - return 0; - StateInfo *stp = st->previous->previous; - do { - stp = stp->previous->previous; - if (stp->key == st->key) - return 1; - i += 2; - } while (i <= e); - st = st->previous; - } + // DTZ stores a 'don't care' value in this case, or even a plain wrong + // one as in case the best move is a losing ep, so it cannot be probed. + if (*result == ZEROING_BEST_MOVE) + return dtz_before_zeroing(wdl); + + int dtz = probe_table(pos, result, wdl); + + if (*result == FAIL) + return 0; + + if (*result != CHANGE_STM) + return (dtz + 100 * (wdl == WDLBlessedLoss || wdl == WDLCursedWin)) * sign_of(wdl); + + // DTZ stores results for the other side, so we need to do a 1-ply search and + // find the winning move that minimizes DTZ. + StateInfo st; + int minDTZ = 0xFFFF; + + for (const Move move : MoveList(pos)) + { + bool zeroing = pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN; + + pos.do_move(move, st); + + // For zeroing moves we want the dtz of the move _before_ doing it, + // otherwise we will get the dtz of the next move sequence. Search the + // position after the move to get the score sign (because even in a + // winning position we could make a losing capture or going for a draw). + dtz = zeroing ? -dtz_before_zeroing(search(pos, result)) + : -probe_dtz(pos, result); + + // If the move mates, force minDTZ to 1 + if (dtz == 1 && pos.checkers() && MoveList(pos).size() == 0) + minDTZ = 1; + + // Convert result from 1-ply search. Zeroing moves are already accounted + // by dtz_before_zeroing() that returns the DTZ of the previous move. + if (!zeroing) + dtz += sign_of(dtz); + + // Skip the draws and if we are winning only pick positive dtz + if (dtz < minDTZ && sign_of(dtz) == sign_of(wdl)) + minDTZ = dtz; + + pos.undo_move(move); + + if (*result == FAIL) + return 0; + } + + // When there are no legal moves, the position is mate: we return -1 + return minDTZ == 0xFFFF ? -1 : minDTZ; } -static Value wdl_to_Value[5] = { - -VALUE_MATE + MAX_PLY + 1, - VALUE_DRAW - 2, - VALUE_DRAW, - VALUE_DRAW + 2, - VALUE_MATE - MAX_PLY - 1 -}; -// Use the DTZ tables to filter out moves that don't preserve the win or draw. -// If the position is lost, but DTZ is fairly high, only keep moves that -// maximise DTZ. +// Use the DTZ tables to rank root moves. // -// A return value false indicates that not all probes were successful and that -// no moves were filtered out. -bool Tablebases::root_probe(Position& pos, Search::RootMoveVector& rootMoves, Value& score) -{ - int success; - - int dtz = probe_dtz(pos, &success); - if (!success) return false; - - StateInfo st; - CheckInfo ci(pos); - - // Probe each move. - for (size_t i = 0; i < rootMoves.size(); i++) { - Move move = rootMoves[i].pv[0]; - pos.do_move(move, st, pos.gives_check(move, ci)); - int v = 0; - if (pos.checkers() && dtz > 0) { - ExtMove s[192]; - if (generate(pos, s) == s) - v = 1; - } - if (!v) { - if (st.rule50 != 0) { - v = -Tablebases::probe_dtz(pos, &success); - if (v > 0) v++; - else if (v < 0) v--; - } else { - v = -Tablebases::probe_wdl(pos, &success); - v = wdl_to_dtz[v + 2]; - } - } - pos.undo_move(move); - if (!success) return false; - rootMoves[i].score = (Value)v; - } - - // Obtain 50-move counter for the root position. - // In Stockfish there seems to be no clean way, so we do it like this: - int cnt50 = st.previous->rule50; - - // Use 50-move counter to determine whether the root position is - // won, lost or drawn. - int wdl = 0; - if (dtz > 0) - wdl = (dtz + cnt50 <= 100) ? 2 : 1; - else if (dtz < 0) - wdl = (-dtz + cnt50 <= 100) ? -2 : -1; - - // Determine the score to report to the user. - score = wdl_to_Value[wdl + 2]; - // If the position is winning or losing, but too few moves left, adjust the - // score to show how close it is to winning or losing. - // NOTE: int(PawnValueEg) is used as scaling factor in score_to_uci(). - if (wdl == 1 && dtz <= 100) - score = (Value)(((200 - dtz - cnt50) * int(PawnValueEg)) / 200); - else if (wdl == -1 && dtz >= -100) - score = -(Value)(((200 + dtz - cnt50) * int(PawnValueEg)) / 200); - - // Now be a bit smart about filtering out moves. - size_t j = 0; - if (dtz > 0) { // winning (or 50-move rule draw) - int best = 0xffff; - for (size_t i = 0; i < rootMoves.size(); i++) { - int v = rootMoves[i].score; - if (v > 0 && v < best) - best = v; - } - int max = best; - // If the current phase has not seen repetitions, then try all moves - // that stay safely within the 50-move budget, if there are any. - if (!has_repeated(st.previous) && best + cnt50 <= 99) - max = 99 - cnt50; - for (size_t i = 0; i < rootMoves.size(); i++) { - int v = rootMoves[i].score; - if (v > 0 && v <= max) - rootMoves[j++] = rootMoves[i]; - } - } else if (dtz < 0) { // losing (or 50-move rule draw) - int best = 0; - for (size_t i = 0; i < rootMoves.size(); i++) { - int v = rootMoves[i].score; - if (v < best) - best = v; - } - // Try all moves, unless we approach or have a 50-move rule draw. - if (-best * 2 + cnt50 < 100) - return true; - for (size_t i = 0; i < rootMoves.size(); i++) { - if (rootMoves[i].score == best) - rootMoves[j++] = rootMoves[i]; - } - } else { // drawing - // Try all moves that preserve the draw. - for (size_t i = 0; i < rootMoves.size(); i++) { - if (rootMoves[i].score == 0) - rootMoves[j++] = rootMoves[i]; +// A return value false indicates that not all probes were successful. +bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) { + + ProbeState result; + StateInfo st; + + // Obtain 50-move counter for the root position + int cnt50 = pos.rule50_count(); + + // Check whether a position was repeated since the last zeroing move. + bool rep = pos.has_repeated(); + + int dtz, bound = Options["Syzygy50MoveRule"] ? 900 : 1; + + // Probe and rank each move + for (auto& m : rootMoves) + { + pos.do_move(m.pv[0], st); + + // Calculate dtz for the current move counting from the root position + if (pos.rule50_count() == 0) + { + // In case of a zeroing move, dtz is one of -101/-1/0/1/101 + WDLScore wdl = -probe_wdl(pos, &result); + dtz = dtz_before_zeroing(wdl); + } + else + { + // Otherwise, take dtz for the new position and correct by 1 ply + dtz = -probe_dtz(pos, &result); + dtz = dtz > 0 ? dtz + 1 + : dtz < 0 ? dtz - 1 : dtz; + } + + // Make sure that a mating move is assigned a dtz value of 1 + if ( pos.checkers() + && dtz == 2 + && MoveList(pos).size() == 0) + dtz = 1; + + pos.undo_move(m.pv[0]); + + if (result == FAIL) + return false; + + // 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)) + : 0; + m.tbRank = r; + + // Determine the score to be displayed for this move. Assign at least + // 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_DRAW + : r > -bound ? Value((std::min(-3, r + 800) * int(PawnValueEg)) / 200) + : -VALUE_MATE + MAX_PLY + 1; } - } - rootMoves.resize(j, Search::RootMove(MOVE_NONE)); - return true; + return true; } -// Use the WDL tables to filter out moves that don't preserve the win or draw. + +// Use the WDL tables to rank root moves. // This is a fallback for the case that some or all DTZ tables are missing. // -// A return value false indicates that not all probes were successful and that -// no moves were filtered out. -bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoveVector& rootMoves, Value& score) -{ - int success; - - int wdl = Tablebases::probe_wdl(pos, &success); - if (!success) return false; - score = wdl_to_Value[wdl + 2]; - - StateInfo st; - CheckInfo ci(pos); - - int best = -2; - - // Probe each move. - for (size_t i = 0; i < rootMoves.size(); i++) { - Move move = rootMoves[i].pv[0]; - pos.do_move(move, st, pos.gives_check(move, ci)); - int v = -Tablebases::probe_wdl(pos, &success); - pos.undo_move(move); - if (!success) return false; - rootMoves[i].score = (Value)v; - if (v > best) - best = v; - } - - size_t j = 0; - for (size_t i = 0; i < rootMoves.size(); i++) { - if (rootMoves[i].score == best) - rootMoves[j++] = rootMoves[i]; - } - rootMoves.resize(j, Search::RootMove(MOVE_NONE)); - - return true; +// 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 }; + + ProbeState result; + StateInfo st; + + bool rule50 = Options["Syzygy50MoveRule"]; + + // Probe and rank each move + for (auto& m : rootMoves) + { + pos.do_move(m.pv[0], st); + + WDLScore wdl = -probe_wdl(pos, &result); + + pos.undo_move(m.pv[0]); + + if (result == FAIL) + return false; + + m.tbRank = WDL_to_rank[wdl + 2]; + + if (!rule50) + wdl = wdl > WDLDraw ? WDLWin + : wdl < WDLDraw ? WDLLoss : WDLDraw; + m.tbScore = WDL_to_value[wdl + 2]; + } + + return true; } +} // namespace Stockfish