X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=816d43f86036505d70369c99ba4df6003392a9a4;hp=25f1cd03f67cfd22024a55e1d67d13fd48f92aec;hb=HEAD;hpb=9afa1d73306cb98e95acec5daf4efd65e592ceff
diff --git a/src/tt.cpp b/src/tt.cpp
index 25f1cd03..816d43f8 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -1,8 +1,6 @@
/*
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) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2004-2023 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
@@ -18,101 +16,146 @@
along with this program. If not, see .
*/
-#include // For std::memset
+#include "tt.h"
+
+#include
+#include
+#include
#include
+#include
+#include
-#include "bitboard.h"
-#include "tt.h"
+#include "misc.h"
+#include "thread.h"
+#include "uci.h"
-TranspositionTable TT; // Our global transposition table
+namespace Stockfish {
+TranspositionTable TT; // Our global transposition table
-/// 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.
+// Populates the TTEntry with a new node's data, possibly
+// overwriting an old position. The update is not atomic and can be racy.
+void TTEntry::save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev) {
-void TranspositionTable::resize(size_t mbSize) {
+ // Preserve any existing move for the same position
+ if (m || uint16_t(k) != key16)
+ move16 = uint16_t(m);
- size_t newClusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
+ // Overwrite less valuable entries (cheapest checks first)
+ if (b == BOUND_EXACT || uint16_t(k) != key16 || d - DEPTH_OFFSET + 2 * pv > depth8 - 4)
+ {
+ assert(d > DEPTH_OFFSET);
+ assert(d < 256 + DEPTH_OFFSET);
- if (newClusterCount == clusterCount)
- return;
+ 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);
+ }
+}
- clusterCount = newClusterCount;
- free(mem);
- mem = malloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1);
+// 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.
+void TranspositionTable::resize(size_t mbSize) {
- if (!mem)
- {
- std::cerr << "Failed to allocate " << mbSize
- << "MB for transposition table." << std::endl;
- exit(EXIT_FAILURE);
- }
+ Threads.main()->wait_for_search_finished();
- table = (Cluster*)((uintptr_t(mem) + CacheLineSize - 1) & ~(CacheLineSize - 1));
- clear();
-}
+ aligned_large_pages_free(table);
+ clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
-/// 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).
+ table = static_cast(aligned_large_pages_alloc(clusterCount * sizeof(Cluster)));
+ if (!table)
+ {
+ std::cerr << "Failed to allocate " << mbSize << "MB for transposition table." << std::endl;
+ exit(EXIT_FAILURE);
+ }
+
+ 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 threads;
+
+ for (size_t idx = 0; idx < size_t(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 = size_t(clusterCount / Options["Threads"]),
+ start = size_t(stride * idx),
+ len =
+ idx != size_t(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. 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.
+// 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.
TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
- TTEntry* const tte = first_entry(key);
- const uint16_t key16 = key >> 48; // Use the high 16 bits as key inside the cluster
-
- for (int i = 0; i < ClusterSize; ++i)
- if (!tte[i].key16 || tte[i].key16 == key16)
- {
- if ((tte[i].genBound8 & 0xFC) != generation8 && tte[i].key16)
- 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)
- // 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;
+ TTEntry* const tte = first_entry(key);
+ const uint16_t key16 = uint16_t(key); // Use the low 16 bits as key inside the cluster
+
+ 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
+
+ return found = bool(tte[i].depth8), &tte[i];
+ }
+
+ // 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];
+
+ return found = false, replace;
}
-/// TranspositionTable::hashfull() returns an approximation of the hashtable
-/// occupation during a search. The hash is x permill full, as per UCI protocol.
+// 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 cnt = 0;
- for (int i = 0; i < 1000 / ClusterSize; i++)
- {
- const TTEntry* tte = &table[i].entry[0];
- for (int j = 0; j < ClusterSize; j++)
- if ((tte[j].genBound8 & 0xFC) == generation8)
- cnt++;
- }
- return cnt;
+ 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;
+
+ return cnt / ClusterSize;
}
+
+} // namespace Stockfish