2008-08-31 23:59:13 -06:00
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/*
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2008-10-19 10:56:28 -06:00
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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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2016-01-02 02:43:25 -07:00
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Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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2020-01-07 13:35:47 -07:00
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Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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2008-08-31 23:59:13 -06:00
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2008-10-19 10:56:28 -06:00
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Stockfish is free software: you can redistribute it and/or modify
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2008-08-31 23:59:13 -06:00
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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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2008-09-06 04:30:07 -06:00
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2008-10-19 10:56:28 -06:00
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Stockfish is distributed in the hope that it will be useful,
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2008-08-31 23:59:13 -06:00
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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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2008-09-06 04:30:07 -06:00
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2008-08-31 23:59:13 -06:00
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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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2014-12-30 02:31:50 -07:00
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#include <cstring> // For std::memset
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2011-01-07 05:00:25 -07:00
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#include <iostream>
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2018-05-14 11:52:21 -06:00
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#include <thread>
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2008-08-31 23:59:13 -06:00
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2012-07-07 12:30:27 -06:00
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#include "bitboard.h"
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#include "misc.h"
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#include "thread.h"
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#include "tt.h"
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#include "uci.h"
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2008-08-31 23:59:13 -06:00
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2011-04-15 10:14:12 -06:00
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TranspositionTable TT; // Our global transposition table
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2019-01-01 06:13:08 -07:00
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/// TTEntry::save populates the TTEntry with a new node's data, possibly
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/// overwriting an old position. Update is not atomic and can be racy.
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void TTEntry::save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev) {
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// Preserve any existing move for the same position
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if (m || (k >> 48) != key16)
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move16 = (uint16_t)m;
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// Overwrite less valuable entries
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if ( (k >> 48) != key16
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|| d - DEPTH_OFFSET > depth8 - 4
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|| b == BOUND_EXACT)
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{
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assert(d >= DEPTH_OFFSET);
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key16 = (uint16_t)(k >> 48);
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value16 = (int16_t)v;
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eval16 = (int16_t)ev;
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genBound8 = (uint8_t)(TT.generation8 | uint8_t(pv) << 2 | b);
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depth8 = (uint8_t)(d - DEPTH_OFFSET);
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}
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}
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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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2014-07-01 04:13:20 -06:00
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void TranspositionTable::resize(size_t mbSize) {
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2018-12-08 15:03:42 -07:00
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Threads.main()->wait_for_search_finished();
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2013-05-01 14:55:23 -06:00
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free(mem);
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2019-12-21 12:41:42 -07:00
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clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
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table = static_cast<Cluster*>(aligned_ttmem_alloc(clusterCount * sizeof(Cluster), &mem));
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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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2018-01-01 02:10:41 -07:00
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clear();
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}
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2018-07-03 16:48:20 -06:00
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/// TranspositionTable::clear() initializes the entire transposition table to zero,
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// in a multi-threaded way.
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void TranspositionTable::clear() {
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std::vector<std::thread> threads;
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2018-12-23 08:10:07 -07:00
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for (size_t idx = 0; idx < Options["Threads"]; ++idx)
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{
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threads.emplace_back([this, idx]() {
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// Thread binding gives faster search on systems with a first-touch policy
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if (Options["Threads"] > 8)
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WinProcGroup::bindThisThread(idx);
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// Each thread will zero its part of the hash table
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const size_t stride = clusterCount / Options["Threads"],
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start = stride * idx,
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len = idx != Options["Threads"] - 1 ?
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stride : clusterCount - start;
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std::memset(&table[start], 0, len * sizeof(Cluster));
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});
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}
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for (std::thread& th: threads)
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th.join();
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}
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2014-12-13 01:27:39 -07:00
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/// TranspositionTable::probe() looks up the current position in the transposition
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/// table. It returns true and a pointer to the TTEntry if the position is found.
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/// Otherwise, it returns false and a pointer to an empty or least valuable TTEntry
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/// to be replaced later. The replace value of an entry is calculated as its depth
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/// minus 8 times its relative age. TTEntry t1 is considered more valuable than
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/// TTEntry t2 if its replace value is greater than that of t2.
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2014-12-13 00:16:35 -07:00
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TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
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TTEntry* const tte = first_entry(key);
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const uint16_t key16 = key >> 48; // Use the high 16 bits as key inside the cluster
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for (int i = 0; i < ClusterSize; ++i)
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if (!tte[i].key16 || tte[i].key16 == key16)
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{
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tte[i].genBound8 = uint8_t(generation8 | (tte[i].genBound8 & 0x7)); // Refresh
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2014-12-13 01:27:39 -07:00
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return found = (bool)tte[i].key16, &tte[i];
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}
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2010-06-28 01:20:34 -06:00
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2014-12-13 00:16:35 -07:00
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// Find an entry to be replaced according to the replacement strategy
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TTEntry* replace = tte;
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for (int i = 1; i < ClusterSize; ++i)
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// Due to our packed storage format for generation and its cyclic
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// nature we add 263 (256 is the modulus plus 7 to keep the unrelated
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// lowest three bits from affecting the result) to calculate the entry
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// age correctly even after generation8 overflows into the next cycle.
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if ( replace->depth8 - ((263 + generation8 - replace->genBound8) & 0xF8)
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> tte[i].depth8 - ((263 + generation8 - tte[i].genBound8) & 0xF8))
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replace = &tte[i];
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2014-12-13 01:27:39 -07:00
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return found = false, replace;
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}
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2015-01-25 00:57:51 -07:00
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2016-09-23 11:28:34 -06:00
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/// TranspositionTable::hashfull() returns an approximation of the hashtable
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/// occupation during a search. The hash is x permill full, as per UCI protocol.
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int TranspositionTable::hashfull() const {
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int cnt = 0;
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2018-12-23 08:10:07 -07:00
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for (int i = 0; i < 1000 / ClusterSize; ++i)
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for (int j = 0; j < ClusterSize; ++j)
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cnt += (table[i].entry[j].genBound8 & 0xF8) == generation8;
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return cnt * 1000 / (ClusterSize * (1000 / ClusterSize));
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}
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