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122 lines
3.9 KiB
C++
122 lines
3.9 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <cstring>
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#include <iostream>
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#include "bitboard.h"
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#include "tt.h"
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TranspositionTable TT; // Our global transposition table
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/// TranspositionTable::resize() sets the size of the transposition table,
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/// measured in megabytes. Transposition table consists of a power of 2 number
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/// of clusters and each cluster consists of ClusterSize number of TTEntry.
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void TranspositionTable::resize(uint64_t mbSize) {
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assert(msb((mbSize << 20) / sizeof(TTEntry)) < 32);
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uint32_t size = ClusterSize << msb((mbSize << 20) / sizeof(TTEntry[ClusterSize]));
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if (hashMask == size - ClusterSize)
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return;
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hashMask = size - ClusterSize;
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free(mem);
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mem = calloc(size * sizeof(TTEntry) + CACHE_LINE_SIZE - 1, 1);
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if (!mem)
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{
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std::cerr << "Failed to allocate " << mbSize
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<< "MB for transposition table." << std::endl;
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exit(EXIT_FAILURE);
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}
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table = (TTEntry*)((uintptr_t(mem) + CACHE_LINE_SIZE - 1) & ~(CACHE_LINE_SIZE - 1));
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}
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/// TranspositionTable::clear() overwrites the entire transposition table
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/// with zeroes. It is called whenever the table is resized, or when the
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/// user asks the program to clear the table (from the UCI interface).
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void TranspositionTable::clear() {
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std::memset(table, 0, (hashMask + ClusterSize) * sizeof(TTEntry));
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}
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/// TranspositionTable::probe() looks up the current position in the
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/// transposition table. Returns a pointer to the TTEntry or NULL if
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/// position is not found.
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const TTEntry* TranspositionTable::probe(const Key key) const {
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TTEntry* tte = first_entry(key);
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uint32_t key32 = key >> 32;
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for (unsigned i = 0; i < ClusterSize; ++i, ++tte)
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if (tte->key32 == key32)
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{
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tte->generation8 = generation; // Refresh
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return tte;
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}
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return NULL;
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}
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/// TranspositionTable::store() writes a new entry containing position key and
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/// valuable information of current position. The lowest order bits of position
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/// key are used to decide in which cluster the position will be placed.
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/// When a new entry is written and there are no empty entries available in the
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/// cluster, it replaces the least valuable of the entries. A TTEntry t1 is considered
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/// to be more valuable than a TTEntry t2 if t1 is from the current search and t2
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/// is from a previous search, or if the depth of t1 is bigger than the depth of t2.
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void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV) {
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TTEntry *tte, *replace;
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uint32_t key32 = key >> 32; // Use the high 32 bits as key inside the cluster
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tte = replace = first_entry(key);
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for (unsigned i = 0; i < ClusterSize; ++i, ++tte)
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{
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if (!tte->key32 || tte->key32 == key32) // Empty or overwrite old
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{
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if (!m)
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m = tte->move(); // Preserve any existing ttMove
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replace = tte;
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break;
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}
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// Implement replace strategy
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if ( ( tte->generation8 == generation || tte->bound() == BOUND_EXACT)
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- (replace->generation8 == generation)
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- (tte->depth16 < replace->depth16) < 0)
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replace = tte;
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}
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replace->save(key32, v, b, d, m, generation, statV);
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}
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