X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=d494c27d4ec654fc705d1f45b11fb844cc47314d;hp=26436806c80fff71d0addb59e255d90fb9e72996;hb=8b8412ef87825d8e341e160585307dc89843b7f6;hpb=eed508b4445057cd26bfb95ab5cd754ac96629fd
diff --git a/src/tt.cpp b/src/tt.cpp
index 26436806..d494c27d 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -1,7 +1,6 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2004-2020 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
@@ -17,32 +16,55 @@
along with this program. If not, see .
*/
-#include
+#include // For std::memset
#include
+#include
#include "bitboard.h"
+#include "misc.h"
+#include "thread.h"
#include "tt.h"
+#include "uci.h"
TranspositionTable TT; // Our global transposition table
+/// TTEntry::save() populates the TTEntry with a new node's data, possibly
+/// overwriting an old position. Update is not atomic and can be racy.
-/// TranspositionTable::set_size() 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 TTEntry::save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev) {
-void TranspositionTable::set_size(size_t mbSize) {
+ // Preserve any existing move for the same position
+ if (m || (uint16_t)k != key16)
+ move16 = (uint16_t)m;
- assert(msb((mbSize << 20) / sizeof(TTEntry)) < 32);
+ // Overwrite less valuable entries
+ if ((uint16_t)k != key16
+ || d - DEPTH_OFFSET > depth8 - 4
+ || b == BOUND_EXACT)
+ {
+ assert(d >= DEPTH_OFFSET);
- uint32_t size = ClusterSize << msb((mbSize << 20) / sizeof(TTEntry[ClusterSize]));
+ key16 = (uint16_t)k;
+ value16 = (int16_t)v;
+ eval16 = (int16_t)ev;
+ genBound8 = (uint8_t)(TT.generation8 | uint8_t(pv) << 2 | b);
+ depth8 = (uint8_t)(d - DEPTH_OFFSET);
+ }
+}
- if (hashMask == size - ClusterSize)
- return;
- hashMask = size - ClusterSize;
- free(mem);
- mem = calloc(size * sizeof(TTEntry) + CACHE_LINE_SIZE - 1, 1);
+/// 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.
+
+void TranspositionTable::resize(size_t mbSize) {
+
+ Threads.main()->wait_for_search_finished();
+ aligned_ttmem_free(mem);
+
+ clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
+ table = static_cast(aligned_ttmem_alloc(clusterCount * sizeof(Cluster), mem));
if (!mem)
{
std::cerr << "Failed to allocate " << mbSize
@@ -50,72 +72,84 @@ void TranspositionTable::set_size(size_t mbSize) {
exit(EXIT_FAILURE);
}
- table = (TTEntry*)((uintptr_t(mem) + CACHE_LINE_SIZE - 1) & ~(CACHE_LINE_SIZE - 1));
+ 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).
+/// TranspositionTable::clear() initializes the entire transposition table to zero,
+// in a multi-threaded way.
void TranspositionTable::clear() {
- std::memset(table, 0, (hashMask + ClusterSize) * sizeof(TTEntry));
-}
+ std::vector threads;
+ for (size_t idx = 0; idx < Options["Threads"]; ++idx)
+ {
+ threads.emplace_back([this, idx]() {
-/// TranspositionTable::probe() looks up the current position in the
-/// transposition table. Returns a pointer to the TTEntry or NULL if
-/// position is not found.
-
-const TTEntry* TranspositionTable::probe(const Key key) const {
+ // Thread binding gives faster search on systems with a first-touch policy
+ if (Options["Threads"] > 8)
+ WinProcGroup::bindThisThread(idx);
- const TTEntry* tte = first_entry(key);
- uint32_t key32 = key >> 32;
+ // 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;
- for (unsigned i = 0; i < ClusterSize; ++i, ++tte)
- if (tte->key() == key32)
- return tte;
+ std::memset(&table[start], 0, len * sizeof(Cluster));
+ });
+ }
- return NULL;
+ for (std::thread& th : threads)
+ th.join();
}
-/// 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.
+/// 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.
-void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV) {
+TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
- int c1, c2, c3;
- TTEntry *tte, *replace;
- uint32_t key32 = key >> 32; // Use the high 32 bits as key inside the cluster
+ TTEntry* const tte = first_entry(key);
+ const uint16_t key16 = (uint16_t)key; // Use the low 16 bits as key inside the cluster
- tte = replace = first_entry(key);
-
- for (unsigned i = 0; i < ClusterSize; ++i, ++tte)
- {
- if (!tte->key() || tte->key() == key32) // Empty or overwrite old
+ for (int i = 0; i < ClusterSize; ++i)
+ if (!tte[i].key16 || tte[i].key16 == key16)
{
- if (!m)
- m = tte->move(); // Preserve any existing ttMove
+ tte[i].genBound8 = uint8_t(generation8 | (tte[i].genBound8 & 0x7)); // Refresh
- replace = tte;
- break;
+ return found = (bool)tte[i].key16, &tte[i];
}
- // Implement replace strategy
- c1 = (replace->generation() == generation ? 2 : 0);
- c2 = (tte->generation() == generation || tte->bound() == BOUND_EXACT ? -2 : 0);
- c3 = (tte->depth() < replace->depth() ? 1 : 0);
+ // 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 263 (256 is the modulus plus 7 to keep the unrelated
+ // lowest three bits from affecting the result) to calculate the entry
+ // age correctly even after generation8 overflows into the next cycle.
+ if ( replace->depth8 - ((263 + generation8 - replace->genBound8) & 0xF8)
+ > tte[i].depth8 - ((263 + generation8 - tte[i].genBound8) & 0xF8))
+ replace = &tte[i];
+
+ return found = false, replace;
+}
- if (c1 + c2 + c3 > 0)
- replace = tte;
- }
- replace->save(key32, v, b, d, m, generation, statV);
+/// 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 cnt = 0;
+ for (int i = 0; i < 1000; ++i)
+ for (int j = 0; j < ClusterSize; ++j)
+ cnt += (table[i].entry[j].genBound8 & 0xF8) == generation8;
+
+ return cnt / ClusterSize;
}