X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=816d43f86036505d70369c99ba4df6003392a9a4;hp=bb49a824519a52b97828b1a6055d2e12cc8f198b;hb=HEAD;hpb=f6f1d2422303923927c0c088dee1d6df22dc4b98

diff --git a/src/tt.cpp b/src/tt.cpp
index bb49a824..816d43f8 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) 2008-2015 Marco Costalba, Joona Kiiski, 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
@@ -17,80 +16,146 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <cstring>   // For std::memset
+#include "tt.h"
+
+#include <cassert>
+#include <cstdlib>
+#include <cstring>
 #include <iostream>
+#include <thread>
+#include <vector>
 
-#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 = size_t(1) << msb((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 = calloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1, 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));
-}
+    aligned_large_pages_free(table);
+
+    clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
+
+    table = static_cast<Cluster*>(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();
+}
 
-/// 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).
 
+// 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 < 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;
 
-/// 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.
+            std::memset(&table[start], 0, len * sizeof(Cluster));
+        });
+    }
+
+    for (std::thread& th : threads)
+        th.join();
+}
 
+
+// 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
+    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;
+}
+
 
-  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
+// Returns an approximation of the hashtable
+// occupation during a search. The hash is x permill full, as per UCI protocol.
 
-          return found = (bool)tte[i].key16, &tte[i];
-      }
+int TranspositionTable::hashfull() const {
 
-  // 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)
-          replace = &tte[i];
+    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 found = false, replace;
+    return cnt / ClusterSize;
 }
+
+}  // namespace Stockfish