/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+ Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
-
- Glaurung is distributed in the hope that it will be useful,
+
+ 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 <cstring> // For std::memset
+#include <iostream>
+#include <thread>
-////
-//// Includes
-////
-
-#include <cassert>
-#include <cmath>
-
+#include "bitboard.h"
+#include "misc.h"
+#include "thread.h"
#include "tt.h"
+#include "uci.h"
+TranspositionTable TT; // Our global transposition table
-////
-//// Functions
-////
+/// TTEntry::save saves a TTEntry
+void TTEntry::save(Key k, Value v, bool PvNode, Bound b, Depth d, Move m, Value ev) {
-/// Constructor
+ assert(d / ONE_PLY * ONE_PLY == d);
-TranspositionTable::TranspositionTable(unsigned mbSize) {
- size = 0;
- generation = 0;
- writes = 0;
- entries = 0;
- this->set_size(mbSize);
-}
+ // Preserve any existing move for the same position
+ if (m || (k >> 48) != key16)
+ move16 = (uint16_t)m;
-
-/// Destructor
-
-TranspositionTable::~TranspositionTable() {
- delete [] entries;
+ // Overwrite less valuable entries
+ if ( (k >> 48) != key16
+ || d / ONE_PLY > depth8 - 4
+ || b == BOUND_EXACT)
+ {
+ key16 = (uint16_t)(k >> 48);
+ value16 = (int16_t)v;
+ eval16 = (int16_t)ev;
+ genBound8 = (uint8_t)(TT.generation8 | PvNode << 2 | b);
+ depth8 = (int8_t)(d / ONE_PLY);
+ }
}
-/// TranspositionTable::set_size sets the size of the transposition table,
-/// measured in megabytes.
+/// TranspositionTable::resize() sets the size of the transposition table,
+/// measured in megabytes. Transposition table consists of a power of 2 number
+/// of clusters and each cluster consists of ClusterSize number of TTEntry.
+
+void TranspositionTable::resize(size_t mbSize) {
-void TranspositionTable::set_size(unsigned mbSize) {
- unsigned newSize;
+ Threads.main()->wait_for_search_finished();
- assert(mbSize >= 4 && mbSize <= 1024);
+ clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
- for(newSize = 1024; newSize * 4 * (sizeof(TTEntry)) <= (mbSize << 20);
- newSize *= 2);
- newSize /= 2;
+ free(mem);
+ mem = malloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1);
- if(newSize != size) {
- size = newSize;
- delete [] entries;
- entries = new TTEntry[size * 4];
- if(entries == NULL) {
+ if (!mem)
+ {
std::cerr << "Failed to allocate " << mbSize
- << " MB for transposition table."
- << std::endl;
+ << "MB for transposition table." << std::endl;
exit(EXIT_FAILURE);
- }
- this->clear();
}
-}
-
-/// TranspositionTable::clear overwrites the entire transposition table
-/// with zeroes. It is called whenever the table is resized, or when the
-/// user asks the program to clear the table (from the UCI interface).
-/// Perhaps we should also clear it when the "ucinewgame" command is recieved?
-
-void TranspositionTable::clear() {
- memset(entries, 0, size * 4 * sizeof(TTEntry));
+ table = (Cluster*)((uintptr_t(mem) + CacheLineSize - 1) & ~(CacheLineSize - 1));
+ clear();
}
-/// TranspositionTable::store writes a new entry containing a position,
-/// a value, a value type, a search depth, and a best move to the
-/// transposition table. The transposition table is organized in clusters
-/// of four TTEntry objects, and when a new entry is written, it replaces
-/// the least valuable of the four entries in a cluster. A TTEntry t1 is
-/// considered to be more valuable than a TTEntry t2 if t1 is from the
-/// current search and t2 is from a previous search, or if the depth of t1
-/// is bigger than the depth of t2.
-
-void TranspositionTable::store(const Position &pos, Value v, Depth d,
- Move m, ValueType type) {
- TTEntry *tte, *replace;
-
- tte = replace = entries + int(pos.get_key() & (size - 1)) * 4;
- for(int i = 0; i < 4; i++) {
- if((tte+i)->key() == pos.get_key()) {
- if(m == MOVE_NONE)
- m = (tte+i)->move();
- *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
- return;
- }
- if(replace->generation() == generation) {
- if((tte+i)->generation() != generation ||
- (tte+i)->depth() < replace->depth())
- replace = tte+i;
- }
- else if((tte+i)->generation() != generation &&
- (tte+i)->depth() < replace->depth())
- replace = tte+i;
- }
- *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
- writes++;
-}
+/// TranspositionTable::clear() initializes the entire transposition table to zero,
+// in a multi-threaded way.
+void TranspositionTable::clear() {
-/// TranspositionTable::retrieve looks up the current position in the
-/// transposition table, and extracts the value, value type, depth and
-/// best move if the position is found. The return value is true if
-/// the position is found, and false if it isn't.
-
-bool TranspositionTable::retrieve(const Position &pos, Value *value,
- Depth *d, Move *move,
- ValueType *type) const {
- TTEntry *tte;
- bool found = false;
-
- tte = entries + int(pos.get_key() & (size - 1)) * 4;
- for(int i = 0; i < 4 && !found ; i++)
- if((tte+i)->key() == pos.get_key()) {
- tte = tte + i;
- found = true;
- }
- if(!found) {
- *move = MOVE_NONE;
- return false;
- }
-
- *value = tte->value();
- *type = tte->type();
- *d = tte->depth();
- *move = tte->move();
-
- return true;
-}
-
-
-/// TranspositionTable::new_search() is called at the beginning of every new
-/// search. It increments the "generation" variable, which is used to
-/// distinguish transposition table entries from previous searches from
-/// entries from the current search.
-
-void TranspositionTable::new_search() {
- generation++;
- writes = 0;
-}
+ std::vector<std::thread> threads;
+ for (size_t idx = 0; idx < Options["Threads"]; ++idx)
+ {
+ threads.emplace_back([this, idx]() {
-/// TranspositionTable::insert_pv() is called at the end of a search
-/// iteration, and inserts the PV back into the PV. This makes sure the
-/// old PV moves are searched first, even if the old TT entries have been
-/// overwritten.
+ // Thread binding gives faster search on systems with a first-touch policy
+ if (Options["Threads"] > 8)
+ WinProcGroup::bindThisThread(idx);
-void TranspositionTable::insert_pv(const Position &pos, Move pv[]) {
- UndoInfo u;
- Position p(pos);
+ // Each thread will zero its part of the hash table
+ const size_t stride = clusterCount / Options["Threads"],
+ start = stride * idx,
+ len = idx != Options["Threads"] - 1 ?
+ stride : clusterCount - start;
- for(int i = 0; pv[i] != MOVE_NONE; i++) {
- this->store(p, VALUE_NONE, Depth(0), pv[i], VALUE_TYPE_NONE);
- p.do_move(pv[i], u);
+ std::memset(&table[start], 0, len * sizeof(Cluster));
+ });
}
-}
-
-/// TranspositionTable::full() returns the permill of all transposition table
-/// entries which have received at least one write during the current search.
-/// It is used to display the "info hashfull ..." information in UCI.
-
-int TranspositionTable::full() {
- double N = double(size) * 4.0;
- return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
+ for (std::thread& th: threads)
+ th.join();
}
+/// TranspositionTable::probe() looks up the current position in the transposition
+/// table. It returns true and a pointer to the TTEntry if the position is found.
+/// Otherwise, it returns false and a pointer to an empty or least valuable TTEntry
+/// to be replaced later. The replace value of an entry is calculated as its depth
+/// minus 8 times its relative age. TTEntry t1 is considered more valuable than
+/// TTEntry t2 if its replace value is greater than that of t2.
-/// Constructors
+TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
-TTEntry::TTEntry() {
-}
+ TTEntry* const tte = first_entry(key);
+ const uint16_t key16 = key >> 48; // Use the high 16 bits as key inside the cluster
-TTEntry::TTEntry(Key k, Value v, ValueType t, Depth d, Move m,
- int generation) {
- key_ = k;
- data = (m & 0x7FFFF) | (t << 20) | (generation << 23);
- value_ = v;
- depth_ = int16_t(d);
-}
+ for (int i = 0; i < ClusterSize; ++i)
+ if (!tte[i].key16 || tte[i].key16 == key16)
+ {
+ tte[i].genBound8 = uint8_t(generation8 | (tte[i].genBound8 & 0x7)); // Refresh
+ return found = (bool)tte[i].key16, &tte[i];
+ }
-/// Functions for extracting data from TTEntry objects.
+ // Find an entry to be replaced according to the replacement strategy
+ TTEntry* replace = tte;
+ for (int i = 1; i < ClusterSize; ++i)
+ // Due to our packed storage format for generation and its cyclic
+ // nature we add 263 (256 is the modulus plus 7 to keep the unrelated
+ // lowest three bits from affecting the result) to calculate the entry
+ // age correctly even after generation8 overflows into the next cycle.
+ if ( replace->depth8 - ((263 + generation8 - replace->genBound8) & 0xF8)
+ > tte[i].depth8 - ((263 + generation8 - tte[i].genBound8) & 0xF8))
+ replace = &tte[i];
-Key TTEntry::key() const {
- return key_;
+ return found = false, replace;
}
-Depth TTEntry::depth() const {
- return Depth(depth_);
-}
-Move TTEntry::move() const {
- return Move(data & 0x7FFFF);
-}
+/// TranspositionTable::hashfull() returns an approximation of the hashtable
+/// occupation during a search. The hash is x permill full, as per UCI protocol.
-Value TTEntry::value() const {
- return Value(value_);
-}
+int TranspositionTable::hashfull() const {
-ValueType TTEntry::type() const {
- return ValueType((data >> 20) & 3);
-}
+ int cnt = 0;
+ for (int i = 0; i < 1000 / ClusterSize; ++i)
+ for (int j = 0; j < ClusterSize; ++j)
+ cnt += (table[i].entry[j].genBound8 & 0xF8) == generation8;
-int TTEntry::generation() const {
- return (data >> 23);
+ return cnt * 1000 / (ClusterSize * (1000 / ClusterSize));
}