X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=16331b8762ae04c60689a341f46af7c3ad49e9c9;hp=268c21f896ab3c89e962ae6dde36c9001030231b;hb=2f6927ac08887ff3b709cfe9228b27a85bdd1d88;hpb=c2c0ba875f429e497c936b61be9f75dcc88385a9

diff --git a/src/tt.cpp b/src/tt.cpp
index 268c21f8..16331b87 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -1,13 +1,14 @@
 /*
-  Glaurung, a UCI chess playing engine.
-  Copyright (C) 2004-2008 Tord Romstad
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
 
-  Glaurung is free software: you can redistribute it and/or modify
+  Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
-  Glaurung is distributed in the hope that it will be useful,
+  Stockfish is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
@@ -23,28 +24,28 @@
 
 #include <cassert>
 #include <cmath>
+#include <cstring>
+#if !defined(NO_PREFETCH)
+#  include <xmmintrin.h>
+#endif
 
+#include "movegen.h"
 #include "tt.h"
 
+// The main transposition table
+TranspositionTable TT;
 
 ////
 //// Functions
 ////
 
-/// Constructor
+TranspositionTable::TranspositionTable() {
 
-TranspositionTable::TranspositionTable(unsigned mbSize) {
-
-  size = 0;
-  generation = 0;
-  writes = 0;
+  size = writes = 0;
   entries = 0;
-  set_size(mbSize);
+  generation = 0;
 }
 
-
-/// Destructor
-
 TranspositionTable::~TranspositionTable() {
 
   delete [] entries;
@@ -54,124 +55,138 @@ TranspositionTable::~TranspositionTable() {
 /// TranspositionTable::set_size sets the size of the transposition table,
 /// measured in megabytes.
 
-void TranspositionTable::set_size(unsigned mbSize) {
+void TranspositionTable::set_size(size_t mbSize) {
 
-  assert(mbSize >= 4 && mbSize <= 1024);
+  size_t newSize = 1024;
 
-  unsigned newSize = 1024;
+  // We store a cluster of ClusterSize number of TTEntry for each position
+  // and newSize is the maximum number of storable positions.
+  while ((2 * newSize) * sizeof(TTCluster) <= (mbSize << 20))
+      newSize *= 2;
 
-  // We store a cluster of 4 TTEntry for each position and newSize is
-  // the maximum number of storable positions
-  for ( ; newSize * 4 * (sizeof(TTEntry)) <= (mbSize << 20); newSize *= 2);
-  newSize /= 2;
   if (newSize != size)
   {
-    size = newSize;
-    delete [] entries;
-    entries = new TTEntry[size * 4];
-    if (!entries)
-    {
-      std::cerr << "Failed to allocate " << mbSize
-                << " MB for transposition table."
-                << std::endl;
-      exit(EXIT_FAILURE);
-    }
-    clear();
+      size = newSize;
+      delete [] entries;
+      entries = new TTCluster[size];
+      if (!entries)
+      {
+          std::cerr << "Failed to allocate " << mbSize
+                    << " MB for transposition table." << std::endl;
+          Application::exit_with_failure();
+      }
+      clear();
   }
 }
 
 
 /// TranspositionTable::clear overwrites the entire transposition table
-/// with zeroes.  It is called whenever the table is resized, or when the
+/// 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).
 /// Perhaps we should also clear it when the "ucinewgame" command is recieved?
 
 void TranspositionTable::clear() {
 
-  memset(entries, 0, size * 4 * sizeof(TTEntry));
+  memset(entries, 0, size * sizeof(TTCluster));
+}
+
+
+/// TranspositionTable::first_entry returns a pointer to the first
+/// entry of a cluster given a position. The low 32 bits of the key
+/// are used to get the index in the table.
+
+inline TTEntry* TranspositionTable::first_entry(const Key posKey) const {
+
+  return entries[uint32_t(posKey) & (size - 1)].data;
 }
 
 
 /// TranspositionTable::store writes a new entry containing a position,
 /// a value, a value type, a search depth, and a best move to the
-/// transposition table.  The transposition table is organized in clusters
-/// of four TTEntry objects, and when a new entry is written, it replaces
-/// the least valuable of the four entries in a cluster.  A TTEntry t1 is
+/// transposition table. Transposition table is organized in clusters of
+/// four TTEntry objects, and when a new entry is written, it replaces
+/// the least valuable of the four entries in a cluster. 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.
+/// is bigger than the depth of t2. A TTEntry of type VALUE_TYPE_EVAL
+/// never replaces another entry for the same position.
+
+void TranspositionTable::store(const Key posKey, Value v, ValueType t, Depth d, Move m, Value statV, Value kingD) {
 
-void TranspositionTable::store(const Position &pos, Value v, Depth d,
-                               Move m, ValueType type) {
   TTEntry *tte, *replace;
+  uint32_t posKey32 = posKey >> 32; // Use the high 32 bits as key
 
-  tte = replace = first_entry(pos);
-  for (int i = 0; i < 4; i++)
+  tte = replace = first_entry(posKey);
+  for (int i = 0; i < ClusterSize; i++, tte++)
   {
-    if (!(tte+i)->key()) // still empty
-    {
-        *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
-        writes++;
-        return;
-    }
-    if ((tte+i)->key() == pos.get_key()) // overwrite old
-    {
-        if (m == MOVE_NONE)
-            m = (tte+i)->move();
-
-        *(tte+i) = TTEntry(pos.get_key(), v, type, d, m, generation);
-        return;
-    }
-    if (   i == 0  // already is (replace == tte+i), common case
-        || replace->generation() < (tte+i)->generation())
-        continue;
-
-    if (    replace->generation() > (tte+i)->generation()
-        || (tte+i)->depth() < replace->depth())
-        replace = tte+i;
+      if (!tte->key() || tte->key() == posKey32) // empty or overwrite old
+      {
+          // Preserve any exsisting ttMove
+          if (m == MOVE_NONE)
+              m = tte->move();
+
+          *tte = TTEntry(posKey32, v, t, d, m, generation, statV, kingD);
+          return;
+      }
+      else if (i == 0)  // replace would be a no-op in this common case
+          continue;
+
+      int c1 = (replace->generation() == generation ?  2 : 0);
+      int c2 = (tte->generation() == generation ? -2 : 0);
+      int c3 = (tte->depth() < replace->depth() ?  1 : 0);
+
+      if (c1 + c2 + c3 > 0)
+          replace = tte;
   }
-  *replace = TTEntry(pos.get_key(), v, type, d, m, generation);
+  *replace = TTEntry(posKey32, v, t, d, m, generation, statV, kingD);
   writes++;
 }
 
 
 /// TranspositionTable::retrieve looks up the current position in the
-/// transposition table, and extracts the value, value type, depth and
-/// best move if the position is found.  The return value is true if
-/// the position is found, and false if it isn't.
+/// transposition table. Returns a pointer to the TTEntry or NULL
+/// if position is not found.
 
-bool TranspositionTable::retrieve(const Position &pos, Value *value,
-                                  Depth *d, Move *move,
-                                  ValueType *type) const {
-  TTEntry *tte = first_entry(pos);
+TTEntry* TranspositionTable::retrieve(const Key posKey) const {
 
-  for (int i = 0; i < 4; i++)
-  {
-      tte += i;
-      if (tte->key() == pos.get_key())
-      {
-          *value = tte->value();
-          *type = tte->type();
-          *d = tte->depth();
-          *move = tte->move();
-          return true;
-      }
-  }
-  *move = MOVE_NONE;
-  return false;
+  uint32_t posKey32 = posKey >> 32;
+  TTEntry* tte = first_entry(posKey);
+
+  for (int i = 0; i < ClusterSize; i++, tte++)
+      if (tte->key() == posKey32)
+          return tte;
+
+  return NULL;
 }
 
 
-/// TranspositionTable::first_entry returns a pointer to the first
-/// entry of a cluster given a position.
+/// TranspositionTable::prefetch looks up the current position in the
+/// transposition table and load it in L1/L2 cache. This is a non
+/// blocking function and do not stalls the CPU waiting for data
+/// to be loaded from RAM, that can be very slow. When we will
+/// subsequently call retrieve() the TT data will be already
+/// quickly accessible in L1/L2 CPU cache.
+#if defined(NO_PREFETCH)
+void TranspositionTable::prefetch(const Key) const {}
+#else
+
+void TranspositionTable::prefetch(const Key posKey) const {
 
-inline TTEntry* TranspositionTable::first_entry(const Position &pos) const {
+#if defined(__INTEL_COMPILER) || defined(__ICL)
+   // This hack prevents prefetches to be optimized away by
+   // Intel compiler. Both MSVC and gcc seems not affected.
+   __asm__ ("");
+#endif
 
-  return entries + (int(pos.get_key() & (size - 1)) << 2);
+   char const* addr = (char*)first_entry(posKey);
+  _mm_prefetch(addr, _MM_HINT_T2);
+  _mm_prefetch(addr+64, _MM_HINT_T2); // 64 bytes ahead
 }
 
+#endif
+
 /// TranspositionTable::new_search() is called at the beginning of every new
-/// search.  It increments the "generation" variable, which is used to
+/// search. It increments the "generation" variable, which is used to
 /// distinguish transposition table entries from previous searches from
 /// entries from the current search.
 
@@ -183,67 +198,62 @@ void TranspositionTable::new_search() {
 
 
 /// TranspositionTable::insert_pv() is called at the end of a search
-/// iteration, and inserts the PV back into the PV.  This makes sure the
-/// old PV moves are searched first, even if the old TT entries have been
-/// overwritten.
+/// iteration, and inserts the PV back into the PV. This makes sure
+/// the old PV moves are searched first, even if the old TT entries
+/// have been overwritten.
 
-void TranspositionTable::insert_pv(const Position &pos, Move pv[]) {
+void TranspositionTable::insert_pv(const Position& pos, Move pv[]) {
 
-  UndoInfo u;
-  Position p(pos);
+  StateInfo st;
+  Position p(pos, pos.thread());
 
   for (int i = 0; pv[i] != MOVE_NONE; i++)
   {
-    store(p, VALUE_NONE, Depth(0), pv[i], VALUE_TYPE_NONE);
-    p.do_move(pv[i], u);
+      TTEntry *tte = retrieve(p.get_key());
+      if (!tte || tte->move() != pv[i])
+          store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, Depth(-127*OnePly), pv[i], VALUE_NONE, VALUE_NONE);
+      p.do_move(pv[i], st);
   }
 }
 
 
-/// TranspositionTable::full() returns the permill of all transposition table
-/// entries which have received at least one write during the current search.
-/// It is used to display the "info hashfull ..." information in UCI.
-
-int TranspositionTable::full() {
+/// TranspositionTable::extract_pv() extends a PV by adding moves from the
+/// transposition table at the end. This should ensure that the PV is almost
+/// always at least two plies long, which is important, because otherwise we
+/// will often get single-move PVs when the search stops while failing high,
+/// and a single-move PV means that we don't have a ponder move.
 
-  double N = double(size) * 4.0;
-  return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
-}
-
-
-/// Constructors
-
-TTEntry::TTEntry() {
-}
+void TranspositionTable::extract_pv(const Position& pos, Move pv[], const int PLY_MAX) {
 
-TTEntry::TTEntry(Key k, Value v, ValueType t, Depth d, Move m,
-                 int generation) :
-  key_ (k), data((m & 0x7FFFF) | (t << 20) | (generation << 23)),
-  value_(v), depth_(int16_t(d)) {}
+  const TTEntry* tte;
+  StateInfo st;
+  Position p(pos, pos.thread());
+  int ply = 0;
 
+  // Update position to the end of current PV
+  while (pv[ply] != MOVE_NONE)
+      p.do_move(pv[ply++], st);
 
-/// Functions for extracting data from TTEntry objects.
-
-inline Key TTEntry::key() const {
-  return key_;
-}
-
-inline Depth TTEntry::depth() const {
-  return Depth(depth_);
+  // Try to add moves from TT while possible
+  while (   (tte = retrieve(p.get_key())) != NULL
+         && tte->move() != MOVE_NONE
+         && move_is_legal(p, tte->move())
+         && (!p.is_draw() || ply < 2)
+         && ply < PLY_MAX)
+  {
+      pv[ply] = tte->move();
+      p.do_move(pv[ply++], st);
+  }
+  pv[ply] = MOVE_NONE;
 }
 
-inline Move TTEntry::move() const {
-  return Move(data & 0x7FFFF);
-}
 
-inline Value TTEntry::value() const {
-  return Value(value_);
-}
+/// TranspositionTable::full() returns the permill of all transposition table
+/// entries which have received at least one write during the current search.
+/// It is used to display the "info hashfull ..." information in UCI.
 
-inline ValueType TTEntry::type() const {
-  return ValueType((data >> 20) & 3);
-}
+int TranspositionTable::full() const {
 
-inline int TTEntry::generation() const {
-  return (data >> 23);
+  double N = double(size) * ClusterSize;
+  return int(1000 * (1 - exp(writes * log(1.0 - 1.0/N))));
 }