/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
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/>.
*/
+#include <cstring> // For std::memset
+#include <iostream>
+#include <thread>
-////
-//// Includes
-////
-
-#include <cassert>
-#include <cmath>
-#include <cstring>
-
+#include "bitboard.h"
+#include "misc.h"
+#include "thread.h"
#include "tt.h"
+#include "uci.h"
+TranspositionTable TT; // Our global transposition table
-////
-//// Functions
-////
+/// TTEntry::save() populates the TTEntry with a new node's data, possibly
+/// overwriting an old position. Update is not atomic and can be racy.
-/// Constructor
+void TTEntry::save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev) {
-TranspositionTable::TranspositionTable(unsigned mbSize) {
+ // Preserve any existing move for the same position
+ if (m || (uint16_t)k != key16)
+ move16 = (uint16_t)m;
- size = 0;
- generation = 0;
- writes = 0;
- entries = 0;
- set_size(mbSize);
+ // Overwrite less valuable entries (cheapest checks first)
+ if (b == BOUND_EXACT
+ || (uint16_t)k != key16
+ || d - DEPTH_OFFSET > depth8 - 4)
+ {
+ assert(d > DEPTH_OFFSET);
+ assert(d < 256 + DEPTH_OFFSET);
+
+ key16 = (uint16_t)k;
+ depth8 = (uint8_t)(d - DEPTH_OFFSET);
+ genBound8 = (uint8_t)(TT.generation8 | uint8_t(pv) << 2 | b);
+ value16 = (int16_t)v;
+ eval16 = (int16_t)ev;
+ }
}
-/// Destructor
-
-TranspositionTable::~TranspositionTable() {
-
- delete [] entries;
-}
-
+/// 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.
-/// TranspositionTable::set_size sets the size of the transposition table,
-/// measured in megabytes.
+void TranspositionTable::resize(size_t mbSize) {
-void TranspositionTable::set_size(unsigned mbSize) {
+ Threads.main()->wait_for_search_finished();
- assert(mbSize >= 4 && mbSize <= 1024);
+ aligned_large_pages_free(table);
- unsigned newSize = 1024;
+ clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
- // We store a cluster of 4 TTEntry for each position and newSize is
- // the maximum number of storable positions
- for ( ; newSize * 4 * (sizeof(TTEntry)) <= (mbSize << 20); newSize *= 2);
- newSize /= 2;
- if (newSize != size)
+ table = static_cast<Cluster*>(aligned_large_pages_alloc(clusterCount * sizeof(Cluster)));
+ if (!table)
{
- size = newSize;
- delete [] entries;
- entries = new TTEntry[size * 4];
- if (!entries)
- {
std::cerr << "Failed to allocate " << mbSize
- << " MB for transposition table."
- << std::endl;
+ << "MB for transposition table." << std::endl;
exit(EXIT_FAILURE);
- }
- clear();
}
+
+ 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?
+/// TranspositionTable::clear() initializes the entire transposition table to zero,
+// in a multi-threaded way.
void TranspositionTable::clear() {
- memset(entries, 0, size * 4 * sizeof(TTEntry));
-}
-
-
-/// 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. A TTEntry of type VALUE_TYPE_EVAL
-/// never replaces another entry for the same position.
+ std::vector<std::thread> threads;
-void TranspositionTable::store(const Position &pos, Value v, Depth d,
- Move m, ValueType type) {
- TTEntry *tte, *replace;
-
- tte = replace = first_entry(pos);
- for (int i = 0; i < 4; i++, tte++)
+ for (size_t idx = 0; idx < Options["Threads"]; ++idx)
{
- if (!tte->key() || tte->key() == pos.get_key()) // empty or overwrite old
- {
- // Do not overwrite position entry when VALUE_TYPE_EVAL
- if ( tte->key()
- && type == VALUE_TYPE_EVAL)
- return;
-
- if (m == MOVE_NONE)
- m = tte->move();
-
- *tte = TTEntry(pos.get_key(), v, type, d, m, generation);
- return;
- }
- else if (i == 0) // replace would be a no-op in this common case
- continue;
-
- int c1 = (replace->generation() == generation ? 2 : 0);
- int c2 = (tte->generation() == generation ? -2 : 0);
- int c3 = (tte->depth() < replace->depth() ? 1 : 0);
-
- if (c1 + c2 + c3 > 0)
- replace = tte;
- }
- *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
- writes++;
-}
+ threads.emplace_back([this, idx]() {
+ // Thread binding gives faster search on systems with a first-touch policy
+ if (Options["Threads"] > 8)
+ WinProcGroup::bindThisThread(idx);
-/// TranspositionTable::retrieve looks up the current position in the
-/// transposition table. Returns a pointer to the TTEntry or NULL
-/// if position is not found.
+ // Each thread will zero its part of the hash table
+ const size_t stride = size_t(clusterCount / Options["Threads"]),
+ start = size_t(stride * idx),
+ len = idx != Options["Threads"] - 1 ?
+ stride : clusterCount - start;
-TTEntry* TranspositionTable::retrieve(const Position &pos) const {
-
- TTEntry *tte = first_entry(pos);
-
- for (int i = 0; i < 4; i++, tte++)
- {
- if (tte->key() == pos.get_key())
- return tte;
+ std::memset(&table[start], 0, len * sizeof(Cluster));
+ });
}
- return NULL;
-}
-
-
-/// TranspositionTable::first_entry returns a pointer to the first
-/// entry of a cluster given a position.
-
-inline TTEntry* TranspositionTable::first_entry(const Position &pos) const {
- return entries + (int(pos.get_key() & (size - 1)) << 2);
+ for (std::thread& th : threads)
+ th.join();
}
-/// 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() {
+/// 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.
- generation++;
- writes = 0;
-}
+TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
+ TTEntry* const tte = first_entry(key);
+ const uint16_t key16 = (uint16_t)key; // Use the low 16 bits as key inside the cluster
-/// 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.
+ for (int i = 0; i < ClusterSize; ++i)
+ if (tte[i].key16 == key16 || !tte[i].depth8)
+ {
+ tte[i].genBound8 = uint8_t(generation8 | (tte[i].genBound8 & (GENERATION_DELTA - 1))); // Refresh
-void TranspositionTable::insert_pv(const Position &pos, Move pv[]) {
+ return found = (bool)tte[i].depth8, &tte[i];
+ }
- StateInfo st;
- Position p(pos);
+ // 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 GENERATION_CYCLE (256 is the modulus, plus what
+ // is needed to keep the unrelated lowest n bits from affecting
+ // the result) to calculate the entry age correctly even after
+ // generation8 overflows into the next cycle.
+ if ( replace->depth8 - ((GENERATION_CYCLE + generation8 - replace->genBound8) & GENERATION_MASK)
+ > tte[i].depth8 - ((GENERATION_CYCLE + generation8 - tte[i].genBound8) & GENERATION_MASK))
+ replace = &tte[i];
- for (int i = 0; pv[i] != MOVE_NONE; i++)
- {
- store(p, VALUE_NONE, Depth(-127*OnePly), pv[i], VALUE_TYPE_NONE);
- p.do_move(pv[i], st);
- }
+ return found = false, replace;
}
-/// 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.
+/// TranspositionTable::hashfull() returns an approximation of the hashtable
+/// occupation during a search. The hash is x permill full, as per UCI protocol.
-int TranspositionTable::full() {
+int TranspositionTable::hashfull() const {
- double N = double(size) * 4.0;
- return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
-}
+ int cnt = 0;
+ for (int i = 0; i < 1000; ++i)
+ for (int j = 0; j < ClusterSize; ++j)
+ cnt += table[i].entry[j].depth8 && (table[i].entry[j].genBound8 & GENERATION_MASK) == generation8;
-
-/// Constructors
-
-TTEntry::TTEntry() {
+ return cnt / ClusterSize;
}
-
-TTEntry::TTEntry(Key k, Value v, ValueType t, Depth d, Move m,
- int generation) :
- key_ (k), data((m & 0x1FFFF) | (t << 20) | (generation << 23)),
- value_(int16_t(v)), depth_(int16_t(d)) {}
projects / stockfish / blobdiff