X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=d3cd094eed966541e84f4ab5b468fef4b626d17f;hp=5ebd10d2d6cdfa7657c3d967716e03f8b848961f;hb=ca7d4e9ac7b5ca74be8aa807fbdf139b2a0860ab;hpb=51330414c4a773a9c3d1dd562fdc8536344a67b8

diff --git a/src/tt.cpp b/src/tt.cpp
index 5ebd10d2..d3cd094e 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -2,6 +2,7 @@
   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
@@ -19,12 +20,40 @@
 
 #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 populates the TTEntry with a new node's data, possibly
+/// overwriting an old position. 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) {
+
+  // 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 - DEPTH_OFFSET > depth8 - 4
+      || b == BOUND_EXACT)
+  {
+      assert(d >= DEPTH_OFFSET);
+
+      key16     = (uint16_t)(k >> 48);
+      value16   = (int16_t)v;
+      eval16    = (int16_t)ev;
+      genBound8 = (uint8_t)(TT.generation8 | uint8_t(pv) << 2 | b);
+      depth8    = (uint8_t)(d - DEPTH_OFFSET);
+  }
+}
+
 
 /// TranspositionTable::resize() sets the size of the transposition table,
 /// measured in megabytes. Transposition table consists of a power of 2 number
@@ -32,15 +61,12 @@ TranspositionTable TT; // Our global transposition table
 
 void TranspositionTable::resize(size_t mbSize) {
 
-  size_t newClusterCount = size_t(1) << msb((mbSize * 1024 * 1024) / sizeof(Cluster));
-
-  if (newClusterCount == clusterCount)
-      return;
+  Threads.main()->wait_for_search_finished();
 
-  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)
   {
@@ -50,25 +76,45 @@ void TranspositionTable::resize(size_t mbSize) {
   }
 
   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. TTEntry t1 is considered more valuable than TTEntry t2 if
-/// both are from the current search and the depth of t1 is greater than the depth of t2,
-/// or if t1 is from a previous search but its depth is at least 8 ply deeper than 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 {
 
@@ -78,8 +124,7 @@ 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].genBound8 & 0x7)); // Refresh
 
           return found = (bool)tte[i].key16, &tte[i];
       }
@@ -87,26 +132,27 @@ TTEntry* TranspositionTable::probe(const Key key, bool& found) 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) * 8 * ONE_PLY +   tte[i].depth8
-          < ((replace->genBound8 & 0xFC) == generation8) * 8 * ONE_PLY + replace->depth8)
+      // 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;
 }
 
 
-/// 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++)
-  {
-      const TTEntry* tte = &table[i].entry[0];
-      for (int j = 0; j < ClusterSize; j++)
-          if ((tte[j].genBound8 & 0xFC) == generation8)
-              cnt++;
-  }
-  return cnt;
+  for (int i = 0; i < 1000 / ClusterSize; ++i)
+      for (int j = 0; j < ClusterSize; ++j)
+          cnt += (table[i].entry[j].genBound8 & 0xF8) == generation8;
+
+  return cnt * 1000 / (ClusterSize * (1000 / ClusterSize));
 }