/*
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (c) 2013 Ronald de Man
- This file may be redistributed and/or modified without restrictions.
+ Copyright (C) 2016-2018 Marco Costalba, Lucas Braesch
- 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.
-#define NOMINMAX
+ Stockfish is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
#include <algorithm>
+#include <atomic>
+#include <cstdint>
+#include <cstring> // For std::memset and std::memcpy
+#include <deque>
+#include <fstream>
+#include <iostream>
+#include <list>
+#include <sstream>
+#include <type_traits>
-#include "../position.h"
-#include "../movegen.h"
#include "../bitboard.h"
+#include "../movegen.h"
+#include "../position.h"
#include "../search.h"
-#include "../bitcount.h"
+#include "../thread_win32.h"
+#include "../types.h"
+#include "../uci.h"
#include "tbprobe.h"
-#include "tbcore.h"
-#include "tbcore.cpp"
+#ifndef _WIN32
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#else
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#endif
-namespace Zobrist {
- extern Key psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
-}
+using namespace Tablebases;
-int Tablebases::MaxCardinality = 0;
+int Tablebases::MaxCardinality;
-// 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<Max15>(pos.pieces(color, pt)); i > 0; i--)
- *str++ = pchr[6 - pt];
- *str++ = 'v';
- color = ~color;
- for (pt = KING; pt >= PAWN; --pt)
- for (i = popcount<Max15>(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 { KEY, 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";
-// 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 MapPawns[SQUARE_NB];
+int MapB1H1H7[SQUARE_NB];
+int MapA1D1D4[SQUARE_NB];
+int MapKK[10][SQUARE_NB]; // [MapA1D1D4][SQUARE_NB]
+
+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<typename T, int Half = sizeof(T) / 2, int End = sizeof(T) - 1>
+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<Max15>(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<Max15>(pos.pieces(color, pt)); i > 0; i--)
- key ^= Zobrist::psq[BLACK][pt][i - 1];
-
- return key;
+ static_assert(std::is_unsigned<T>::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>(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<typename T, int LE> 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<true >(d, idx)
- : decompress_pairs<false>(d, idx);
+// Return the sign of a number (-1, 0, 1)
+template <typename T> 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<Side S>
+ 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);
+ *mapping = statbuf.st_size;
+ *baseAddress = mmap(nullptr, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0);
+ ::close(fd);
+
+ if (*baseAddress == MAP_FAILED) {
+ std::cerr << "Could not mmap() " << fname << std::endl;
+ exit(1);
+ }
+#else
+ HANDLE fd = CreateFile(fname.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr,
+ OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+
+ if (fd == INVALID_HANDLE_VALUE)
+ return *baseAddress = nullptr, nullptr;
+
+ DWORD size_high;
+ DWORD size_low = GetFileSize(fd, &size_high);
+ HANDLE mmap = CreateFileMapping(fd, nullptr, PAGE_READONLY, size_high, size_low, nullptr);
+ CloseHandle(fd);
+
+ if (!mmap) {
+ std::cerr << "CreateFileMapping() failed" << std::endl;
+ exit(1);
+ }
+
+ *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(1);
+ }
+#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<uint64_t> base64; // base64[l - min_sym_len] is the 64bit-padded lowest symbol of length l
+ std::vector<uint8_t> 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<TBType Type>
+struct TBTable {
+ typedef typename std::conditional<Type == WDL, WDLScore, int>::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];
}
- idx = encode_pawn(entry, entry->file[f].norm[bside], p, entry->file[f].factor[bside]);
- res = decompress_pairs(entry->file[f].precomp[bside], idx);
- }
- return ((int)res) - 2;
+ TBTable() : ready(false), baseAddress(nullptr) {}
+ explicit TBTable(const std::string& code);
+ explicit TBTable(const TBTable<WDL>& wdl);
+
+ ~TBTable() {
+ if (baseAddress)
+ TBFile::unmap(baseAddress, mapping);
+ }
+};
+
+template<>
+TBTable<WDL>::TBTable(const std::string& code) : TBTable() {
+
+ StateInfo st;
+ Position pos;
+
+ key = pos.set(code, WHITE, &st).material_key();
+ pieceCount = pos.count<ALL_PIECES>();
+ hasPawns = pos.pieces(PAWN);
+
+ hasUniquePieces = false;
+ for (Color c = WHITE; c <= BLACK; ++c)
+ 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<PAWN>(BLACK)
+ || ( pos.count<PAWN>(WHITE)
+ && pos.count<PAWN>(BLACK) >= pos.count<PAWN>(WHITE));
+
+ pawnCount[0] = pos.count<PAWN>(c ? WHITE : BLACK);
+ pawnCount[1] = pos.count<PAWN>(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<DTZ>::TBTable(const TBTable<WDL>& 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 {
+
+ typedef std::tuple<Key, TBTable<WDL>*, TBTable<DTZ>*> Entry;
+
+ 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<TBTable<WDL>> wdlTable;
+ std::deque<TBTable<DTZ>> dtzTable;
+
+ 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);
+
+ // 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])) {
+ 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) {
+ swap(entry, hashTable[bucket]);
+ key = otherKey;
+ homeBucket = otherHomeBucket;
+ }
+ }
+ std::cerr << "TB hash table size too low!" << std::endl;
+ exit(1);
+ }
+
+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);
+ }
+ }
+
+ void clear() {
+ memset(hashTable, 0, sizeof(hashTable));
+ wdlTable.clear();
+ dtzTable.clear();
+ }
+ size_t size() const { return wdlTable.size(); }
+ void add(const std::vector<PieceType>& pieces);
+};
+
+TBTables TBTables;
+
+// If the corresponding file exists two new objects TBTable<WDL> and TBTable<DTZ>
+// are created and added to the lists and hash table. Called at init time.
+void TBTables::add(const std::vector<PieceType>& 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 = idx / d->span;
+
+ // Then we read the corresponding SparseIndex[] entry
+ uint32_t block = number<uint32_t, LittleEndian>(&d->sparseIndex[k].block);
+ int offset = number<uint16_t, LittleEndian>(&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<uint64_t, BigEndian>(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 = (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]);
+
+ // 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<uint32_t, BigEndian>(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<LR::Left>();
+
+ // 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<LR::Right>();
+ }
}
- } 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<LR::Left>();
+}
+
+bool check_dtz_stm(TBTable<WDL>*, int, File) { return true; }
+
+bool check_dtz_stm(TBTable<DTZ>* 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<WDL>*, File, int value, WDLScore) { return WDLScore(value - 2); }
+
+int map_score(TBTable<DTZ>* 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<typename T, typename Ret = typename T::Ret>
+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) * 070;
+ 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_of(squares[0]);
+ if (tbFile > FILE_D)
+ tbFile = file_of(squares[0] ^ 7); // Horizontal flip: SQ_H1 -> SQ_A1
}
- 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; ++i)
+ for (int j = i; 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] ^= 7; // Horizontal flip: SQ_H1 -> SQ_A1
+
+ // 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);
+
+ 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
+ // 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
+
+ // 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_C3
+ for (int j = i; j < size; ++j)
+ squares[j] = Square(((squares[j] >> 3) | (squares[j] << 3)) & 63);
+ break;
}
- 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);
+
+ // 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::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];
+ }
+
+ remainingPawns = false;
+ idx += n * d->groupIdx[next];
+ groupSq += d->groupLen[next];
}
- 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];
+ // Now that we have the index, decompress the pair and get the score
+ return map_score(entry, tbFile, decompress_pairs(d, idx), wdl);
+}
- if (!(entry->flags[f] & pa_flags[wdl + 2]) || (wdl & 1))
- res *= 2;
- }
+// 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<typename T>
+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++];
+ }
- return res;
+ d->groupIdx[n] = idx;
}
-// 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));
+// 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<bool>& visited) {
+
+ visited[s] = true; // We can set it now because tree is acyclic
+ Sym sr = d->btree[s].get<LR::Right>();
+
+ if (sr == 0xFFF)
+ return 0;
+
+ Sym sl = d->btree[s].get<LR::Left>();
+
+ 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 = (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[]
+ // 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 http://www.eecs.harvard.edu/~michaelm/E210/huffman.pdf
+ 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;
+
+ 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<uint16_t, LittleEndian>(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<bool> 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<CAPTURES>(pos, stack);
- // Since underpromotion captures are not included, we need to add them.
- end = add_underprom_caps(pos, stack, end);
- } else
- end = generate<EVASIONS>(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, ci, 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<WDL>&, uint8_t* data, File) { return data; }
+
+uint8_t* set_dtz_map(TBTable<DTZ>& 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<uint16_t, LittleEndian>(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<typename T>
+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<CAPTURES>(pos, stack);
- else
- end = generate<EVASIONS>(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, ci, 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<QUIETS>(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 == !!(*data & HasPawns));
+ assert((e.key != e.key2) == !!(*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<TBType Type>
+void* mapped(TBTable<Type>& e, const Position& pos) {
- wdl = probe_ab(pos, -2, 2, success);
- if (*success == 0) return 0;
+ static Mutex mutex;
- if (wdl == 0) return 0;
+ // Use 'aquire' to avoid a thread reads 'ready' == true while another is
+ // still working, this could happen due to compiler reordering.
+ if (e.ready.load(std::memory_order_acquire))
+ return e.baseAddress; // Could be nullptr if file does not exsist
- if (*success == 2)
- return wdl == 2 ? 1 : 101;
+ std::unique_lock<Mutex> 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<NON_EVASIONS>(pos, stack);
- else
- end = generate<EVASIONS>(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, ci, 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, ci, 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<TBType Type, typename Ret = typename TBTable<Type>::Ret>
+Ret probe_table(const Position& pos, ProbeState* result, WDLScore wdl = WDLDraw) {
+
+ if (pos.count<ALL_PIECES>() == 2) // KvK
+ return Ret(WDLDraw);
+
+ TBTable<Type>* entry = TBTables.get<Type>(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<bool CheckZeroingMoves>
+WDLScore search(Position& pos, ProbeState* result) {
+
+ WDLScore value, bestValue = WDLLoss;
+ StateInfo st;
+
+ auto moveList = MoveList<LEGAL>(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<false>(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<NON_EVASIONS>(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<EVASIONS>(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, ci, 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<WDL>(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 == "<empty>")
+ 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<Square> 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<std::pair<int, Square>> 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.push_back(std::make_pair(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[sq ^ 7] = availableSquares--; // Horizontal flip
+ }
+ 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 exsists
+ 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<false>(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
//
// 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<CAPTURES>(pos, stack);
- else
- end = generate<EVASIONS>(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, ci, 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<QUIETS>(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<true>(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<DTZ>(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<LEGAL>(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<false>(pos, result))
+ : -probe_dtz(pos, result);
+
+ // If the move mates, force minDTZ to 1
+ if (dtz == 1 && pos.checkers() && MoveList<LEGAL>(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, ci, pos.gives_check(move, ci));
- int v = 0;
- if (pos.checkers() && dtz > 0) {
- ExtMove s[192];
- if (generate<LEGAL>(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<LEGAL>(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, ci, 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;
+}
projects / stockfish / blobdiff