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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <cstring> // For std::memset
#include <iostream>
+#include <thread>
#include "bitboard.h"
+#include "misc.h"
+#include "thread.h"
#include "tt.h"
+#include "uci.h"
TranspositionTable TT; // Our global transposition table
+/// TTEntry::save saves a TTEntry
+void TTEntry::save(Key k, Value v, Bound b, Depth d, Move m, Value ev) {
+
+ assert(d / ONE_PLY * ONE_PLY == d);
+
+ // Preserve any existing move for the same position
+ if (m || (k >> 48) != key16)
+ move16 = (uint16_t)m;
+
+ // 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 | b);
+ depth8 = (int8_t)(d / ONE_PLY);
+ }
+}
+
/// TranspositionTable::resize() sets the size of the transposition table,
/// measured in megabytes. Transposition table consists of a power of 2 number
void TranspositionTable::resize(size_t mbSize) {
- size_t newClusterCount = size_t(1) << msb((mbSize * 1024 * 1024) / sizeof(Cluster));
+ Threads.main()->wait_for_search_finished();
- if (newClusterCount == clusterCount)
- return;
-
- clusterCount = newClusterCount;
+ clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
free(mem);
- mem = calloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1, 1);
+ mem = malloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1);
if (!mem)
{
}
table = (Cluster*)((uintptr_t(mem) + CacheLineSize - 1) & ~(CacheLineSize - 1));
+ clear();
}
-/// TranspositionTable::clear() overwrites the entire transposition table
-/// with zeros. It is called whenever the table is resized, or when the
-/// user asks the program to clear the table (from the UCI interface).
+/// TranspositionTable::clear() initializes the entire transposition table to zero,
+// in a multi-threaded way.
void TranspositionTable::clear() {
- std::memset(table, 0, clusterCount * sizeof(Cluster));
-}
+ std::vector<std::thread> threads;
+ for (size_t idx = 0; idx < Options["Threads"]; idx++)
+ {
+ threads.emplace_back([this, idx]() {
+
+ // Thread binding gives faster search on systems with a first-touch policy
+ if (Options["Threads"] > 8)
+ WinProcGroup::bindThisThread(idx);
+
+ // 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;
+
+ std::memset(&table[start], 0, len * sizeof(Cluster));
+ });
+ }
+
+ 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. 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.
+/// 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.
TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
for (int i = 0; i < ClusterSize; ++i)
if (!tte[i].key16 || tte[i].key16 == key16)
{
- if (tte[i].key16)
- tte[i].genBound8 = uint8_t(generation8 | tte[i].bound()); // Refresh
+ tte[i].genBound8 = uint8_t(generation8 | tte[i].bound()); // Refresh
return found = (bool)tte[i].key16, &tte[i];
}
// Find an entry to be replaced according to the replacement strategy
TTEntry* replace = tte;
for (int i = 1; i < ClusterSize; ++i)
- if ( (( tte[i].genBound8 & 0xFC) == generation8 || tte[i].bound() == BOUND_EXACT)
- - ((replace->genBound8 & 0xFC) == generation8)
- - (tte[i].depth8 < replace->depth8) < 0)
+ // Due to our packed storage format for generation and its cyclic
+ // nature we add 259 (256 is the modulus plus 3 to keep the lowest
+ // two bound bits from affecting the result) to calculate the entry
+ // age correctly even after generation8 overflows into the next cycle.
+ if ( replace->depth8 - ((259 + generation8 - replace->genBound8) & 0xFC) * 2
+ > tte[i].depth8 - ((259 + generation8 - tte[i].genBound8) & 0xFC) * 2)
replace = &tte[i];
return found = false, replace;
}
-/// Returns an approximation of the hashtable occupation during a search. The
-/// hash is x permill full, as per UCI protocol.
+/// TranspositionTable::hashfull() returns an approximation of the hashtable
+/// occupation during a search. The hash is x permill full, as per UCI protocol.
+
+int TranspositionTable::hashfull() const {
-int TranspositionTable::hashfull() const
-{
int cnt = 0;
for (int i = 0; i < 1000 / ClusterSize; i++)
{
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