2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
36 TranspositionTable::TranspositionTable(unsigned mbSize) {
41 this->set_size(mbSize);
47 TranspositionTable::~TranspositionTable() {
52 /// TranspositionTable::set_size sets the size of the transposition table,
53 /// measured in megabytes.
55 void TranspositionTable::set_size(unsigned mbSize) {
58 assert(mbSize >= 4 && mbSize <= 1024);
60 for(newSize = 1024; newSize * 4 * (sizeof(TTEntry)) <= (mbSize << 20);
67 entries = new TTEntry[size * 4];
69 std::cerr << "Failed to allocate " << mbSize
70 << " MB for transposition table."
79 /// TranspositionTable::clear overwrites the entire transposition table
80 /// with zeroes. It is called whenever the table is resized, or when the
81 /// user asks the program to clear the table (from the UCI interface).
82 /// Perhaps we should also clear it when the "ucinewgame" command is recieved?
84 void TranspositionTable::clear() {
85 memset(entries, 0, size * 4 * sizeof(TTEntry));
89 /// TranspositionTable::store writes a new entry containing a position,
90 /// a value, a value type, a search depth, and a best move to the
91 /// transposition table. The transposition table is organized in clusters
92 /// of four TTEntry objects, and when a new entry is written, it replaces
93 /// the least valuable of the four entries in a cluster. A TTEntry t1 is
94 /// considered to be more valuable than a TTEntry t2 if t1 is from the
95 /// current search and t2 is from a previous search, or if the depth of t1
96 /// is bigger than the depth of t2.
98 void TranspositionTable::store(const Position &pos, Value v, Depth d,
99 Move m, ValueType type) {
100 TTEntry *tte, *replace;
102 tte = replace = entries + int(pos.get_key() & (size - 1)) * 4;
103 for(int i = 0; i < 4; i++) {
104 if((tte+i)->key() == pos.get_key()) {
107 *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
110 if(replace->generation() == generation) {
111 if((tte+i)->generation() != generation ||
112 (tte+i)->depth() < replace->depth())
115 else if((tte+i)->generation() != generation &&
116 (tte+i)->depth() < replace->depth())
119 *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
124 /// TranspositionTable::retrieve looks up the current position in the
125 /// transposition table, and extracts the value, value type, depth and
126 /// best move if the position is found. The return value is true if
127 /// the position is found, and false if it isn't.
129 bool TranspositionTable::retrieve(const Position &pos, Value *value,
130 Depth *d, Move *move,
131 ValueType *type) const {
135 tte = entries + int(pos.get_key() & (size - 1)) * 4;
136 for(int i = 0; i < 4 && !found ; i++)
137 if((tte+i)->key() == pos.get_key()) {
146 *value = tte->value();
155 /// TranspositionTable::new_search() is called at the beginning of every new
156 /// search. It increments the "generation" variable, which is used to
157 /// distinguish transposition table entries from previous searches from
158 /// entries from the current search.
160 void TranspositionTable::new_search() {
166 /// TranspositionTable::insert_pv() is called at the end of a search
167 /// iteration, and inserts the PV back into the PV. This makes sure the
168 /// old PV moves are searched first, even if the old TT entries have been
171 void TranspositionTable::insert_pv(const Position &pos, Move pv[]) {
175 for(int i = 0; pv[i] != MOVE_NONE; i++) {
176 this->store(p, VALUE_NONE, Depth(0), pv[i], VALUE_TYPE_NONE);
182 /// TranspositionTable::full() returns the permill of all transposition table
183 /// entries which have received at least one write during the current search.
184 /// It is used to display the "info hashfull ..." information in UCI.
186 int TranspositionTable::full() {
187 double N = double(size) * 4.0;
188 return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
197 TTEntry::TTEntry(Key k, Value v, ValueType t, Depth d, Move m,
200 data = (m & 0x7FFFF) | (t << 20) | (generation << 23);
206 /// Functions for extracting data from TTEntry objects.
208 Key TTEntry::key() const {
212 Depth TTEntry::depth() const {
213 return Depth(depth_);
216 Move TTEntry::move() const {
217 return Move(data & 0x7FFFF);
220 Value TTEntry::value() const {
221 return Value(value_);
224 ValueType TTEntry::type() const {
225 return ValueType((data >> 20) & 3);
228 int TTEntry::generation() const {