/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
-#include <cassert>
#include <cstring>
+#include <iostream>
-#include "evaluate.h"
#include "tt.h"
-// The main transposition table
-TranspositionTable TT;
-
-////
-//// Functions
-////
+TranspositionTable TT; // Our global transposition table
TranspositionTable::TranspositionTable() {
- size = 0;
- entries = 0;
- generation = 0;
+ size = generation = 0;
+ entries = NULL;
}
TranspositionTable::~TranspositionTable() {
}
-/// TranspositionTable::set_size sets the size of the transposition table,
+/// TranspositionTable::set_size() sets the size of the transposition table,
/// measured in megabytes.
void TranspositionTable::set_size(size_t mbSize) {
size_t newSize = 1024;
- // We store a cluster of ClusterSize number of TTEntry for each position
- // and newSize is the maximum number of storable positions.
- while ((2 * newSize) * sizeof(TTCluster) <= (mbSize << 20))
+ // Transposition table consists of clusters and each cluster consists
+ // of ClusterSize number of TTEntries. Each non-empty entry contains
+ // information of exactly one position and newSize is the number of
+ // clusters we are going to allocate.
+ while (2ULL * newSize * sizeof(TTCluster) <= (mbSize << 20))
newSize *= 2;
- if (newSize != size)
+ if (newSize == size)
+ return;
+
+ size = newSize;
+ delete [] entries;
+ entries = new (std::nothrow) TTCluster[size];
+ if (!entries)
{
- size = newSize;
- delete [] entries;
- entries = new TTCluster[size];
- if (!entries)
- {
- std::cerr << "Failed to allocate " << mbSize
- << " MB for transposition table." << std::endl;
- Application::exit_with_failure();
- }
+ std::cerr << "Failed to allocate " << mbSize
+ << "MB for transposition table." << std::endl;
+ exit(EXIT_FAILURE);
}
+ clear();
}
-/// TranspositionTable::clear overwrites the entire transposition table
+/// 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() {
}
-/// 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. 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. A TTEntry of type VALUE_TYPE_EVAL
-/// never replaces another entry for the same position.
+/// TranspositionTable::store() writes a new entry containing position key and
+/// valuable information of current position. The lowest order bits of position
+/// key are used to decide on which cluster the position will be placed.
+/// When a new entry is written and there are no empty entries available in cluster,
+/// it replaces the least valuable of entries. 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 Key posKey, Value v, ValueType t, Depth d, Move m, Value statV, Value kingD) {
+void TranspositionTable::store(const Key posKey, Value v, Bound t, Depth d, Move m, Value statV, Value kingD) {
int c1, c2, c3;
TTEntry *tte, *replace;
- uint32_t posKey32 = posKey >> 32; // Use the high 32 bits as key
+ uint32_t posKey32 = posKey >> 32; // Use the high 32 bits as key inside the cluster
tte = replace = first_entry(posKey);
+
for (int i = 0; i < ClusterSize; i++, tte++)
{
- if (!tte->key() || tte->key() == posKey32) // empty or overwrite old
+ if (!tte->key() || tte->key() == posKey32) // Empty or overwrite old
{
- // Preserve any exsisting ttMove
+ // Preserve any existing ttMove
if (m == MOVE_NONE)
m = tte->move();
return;
}
- if (i == 0) // replace would be a no-op in this common case
- continue;
-
+ // Implement replace strategy
c1 = (replace->generation() == generation ? 2 : 0);
- c2 = (tte->generation() == generation ? -2 : 0);
+ c2 = (tte->generation() == generation || tte->type() == BOUND_EXACT ? -2 : 0);
c3 = (tte->depth() < replace->depth() ? 1 : 0);
if (c1 + c2 + c3 > 0)
}
-/// TranspositionTable::retrieve looks up the current position in the
-/// transposition table. Returns a pointer to the TTEntry or NULL
-/// if position is not found.
+/// TranspositionTable::probe() looks up the current position in the
+/// transposition table. Returns a pointer to the TTEntry or NULL if
+/// position is not found.
-TTEntry* TranspositionTable::retrieve(const Key posKey) const {
+TTEntry* TranspositionTable::probe(const Key posKey) const {
uint32_t posKey32 = posKey >> 32;
TTEntry* tte = first_entry(posKey);
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