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) {
48 TranspositionTable::~TranspositionTable() {
54 /// TranspositionTable::set_size sets the size of the transposition table,
55 /// measured in megabytes.
57 void TranspositionTable::set_size(unsigned mbSize) {
59 assert(mbSize >= 4 && mbSize <= 1024);
61 unsigned newSize = 1024;
63 // We store a cluster of 4 TTEntry for each position and newSize is
64 // the maximum number of storable positions
65 for ( ; newSize * 4 * (sizeof(TTEntry)) <= (mbSize << 20); newSize *= 2);
71 entries = new TTEntry[size * 4];
74 std::cerr << "Failed to allocate " << mbSize
75 << " MB for transposition table."
84 /// TranspositionTable::clear overwrites the entire transposition table
85 /// with zeroes. It is called whenever the table is resized, or when the
86 /// user asks the program to clear the table (from the UCI interface).
87 /// Perhaps we should also clear it when the "ucinewgame" command is recieved?
89 void TranspositionTable::clear() {
91 memset(entries, 0, size * 4 * sizeof(TTEntry));
95 /// TranspositionTable::store writes a new entry containing a position,
96 /// a value, a value type, a search depth, and a best move to the
97 /// transposition table. The transposition table is organized in clusters
98 /// of four TTEntry objects, and when a new entry is written, it replaces
99 /// the least valuable of the four entries in a cluster. A TTEntry t1 is
100 /// considered to be more valuable than a TTEntry t2 if t1 is from the
101 /// current search and t2 is from a previous search, or if the depth of t1
102 /// is bigger than the depth of t2.
104 void TranspositionTable::store(const Position &pos, Value v, Depth d,
105 Move m, ValueType type) {
106 TTEntry *tte, *replace;
108 tte = replace = first_entry(pos);
109 for (int i = 0; i < 4; i++)
111 if (!(tte+i)->key()) // still empty
113 *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
117 if ((tte+i)->key() == pos.get_key()) // overwrite old
122 *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
125 if ( i == 0 // already is (replace == tte+i), common case
126 || replace->generation() < (tte+i)->generation())
129 if ( replace->generation() > (tte+i)->generation()
130 || (tte+i)->depth() < replace->depth())
133 *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
138 /// TranspositionTable::retrieve looks up the current position in the
139 /// transposition table, and extracts the value, value type, depth and
140 /// best move if the position is found. The return value is true if
141 /// the position is found, and false if it isn't.
143 bool TranspositionTable::retrieve(const Position &pos, Value *value,
144 Depth *d, Move *move,
145 ValueType *type) const {
146 TTEntry *tte = first_entry(pos);
148 for (int i = 0; i < 4; i++)
151 if (tte->key() == pos.get_key())
153 *value = tte->value();
165 /// TranspositionTable::first_entry returns a pointer to the first
166 /// entry of a cluster given a position.
168 inline TTEntry* TranspositionTable::first_entry(const Position &pos) const {
170 return entries + (int(pos.get_key() & (size - 1)) << 2);
173 /// TranspositionTable::new_search() is called at the beginning of every new
174 /// search. It increments the "generation" variable, which is used to
175 /// distinguish transposition table entries from previous searches from
176 /// entries from the current search.
178 void TranspositionTable::new_search() {
185 /// TranspositionTable::insert_pv() is called at the end of a search
186 /// iteration, and inserts the PV back into the PV. This makes sure the
187 /// old PV moves are searched first, even if the old TT entries have been
190 void TranspositionTable::insert_pv(const Position &pos, Move pv[]) {
195 for (int i = 0; pv[i] != MOVE_NONE; i++)
197 store(p, VALUE_NONE, Depth(0), pv[i], VALUE_TYPE_NONE);
203 /// TranspositionTable::full() returns the permill of all transposition table
204 /// entries which have received at least one write during the current search.
205 /// It is used to display the "info hashfull ..." information in UCI.
207 int TranspositionTable::full() {
209 double N = double(size) * 4.0;
210 return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
219 TTEntry::TTEntry(Key k, Value v, ValueType t, Depth d, Move m,
221 key_ (k), data((m & 0x7FFFF) | (t << 20) | (generation << 23)),
222 value_(v), depth_(int16_t(d)) {}
225 /// Functions for extracting data from TTEntry objects.
227 inline Key TTEntry::key() const {
231 inline Depth TTEntry::depth() const {
232 return Depth(depth_);
235 inline Move TTEntry::move() const {
236 return Move(data & 0x7FFFF);
239 inline Value TTEntry::value() const {
240 return Value(value_);
243 inline ValueType TTEntry::type() const {
244 return ValueType((data >> 20) & 3);
247 inline int TTEntry::generation() const {