X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=7e501fc41fa1278b143222641ffe414085a690b5;hp=21aa4f92069dbcbbf7997b73364b641444fc9ed2;hb=8acb1d7e4ddb9627ed3c2910f6c47f466b94ad90;hpb=4634be8ba6176e71579fa01f5fd2c74e41eedad6

diff --git a/src/search.cpp b/src/search.cpp
index 21aa4f92..7e501fc4 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008 Marco Costalba
+  Copyright (C) 2008-2009 Marco Costalba
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -23,6 +23,7 @@
 ////
 
 #include <cassert>
+#include <cstring>
 #include <fstream>
 #include <iostream>
 #include <sstream>
@@ -31,7 +32,9 @@
 #include "evaluate.h"
 #include "history.h"
 #include "misc.h"
+#include "movegen.h"
 #include "movepick.h"
+#include "lock.h"
 #include "san.h"
 #include "search.h"
 #include "thread.h"
@@ -71,7 +74,8 @@ namespace {
   // Apart for the first one that has its score, following moves
   // normally have score -VALUE_INFINITE, so are ordered according
   // to the number of beta cutoffs occurred under their subtree during
-  // the last iteration.
+  // the last iteration. The counters are per thread variables to avoid
+  // concurrent accessing under SMP case.
 
   struct BetaCounterType {
 
@@ -79,8 +83,6 @@ namespace {
     void clear();
     void add(Color us, Depth d, int threadID);
     void read(Color us, int64_t& our, int64_t& their);
-
-    int64_t hits[THREAD_MAX][2];
   };
 
 
@@ -107,7 +109,7 @@ namespace {
   class RootMoveList {
 
   public:
-    RootMoveList(Position &pos, Move searchMoves[]);
+    RootMoveList(Position& pos, Move searchMoves[]);
     inline Move get_move(int moveNum) const;
     inline Value get_move_score(int moveNum) const;
     inline void set_move_score(int moveNum, Value score);
@@ -128,99 +130,98 @@ namespace {
   };
 
 
-  /// Constants and variables
-
-  // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
-  // nodes:
-  int LMRPVMoves = 15;
-  int LMRNonPVMoves = 4;
+  /// Constants
 
-  // Depth limit for use of dynamic threat detection:
-  Depth ThreatDepth = 5*OnePly;
+  // Search depth at iteration 1
+  const Depth InitialDepth = OnePly /*+ OnePly/2*/;
 
-  // Depth limit for selective search:
-  Depth SelectiveDepth = 7*OnePly;
+  // Depth limit for selective search
+  const Depth SelectiveDepth = 7 * OnePly;
 
   // Use internal iterative deepening?
   const bool UseIIDAtPVNodes = true;
   const bool UseIIDAtNonPVNodes = false;
 
-  // Internal iterative deepening margin.  At Non-PV moves, when
-  // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
-  // when the static evaluation is at most IIDMargin below beta.
+  // Internal iterative deepening margin. At Non-PV moves, when
+  // UseIIDAtNonPVNodes is true, we do an internal iterative deepening
+  // search when the static evaluation is at most IIDMargin below beta.
   const Value IIDMargin = Value(0x100);
 
-  // Easy move margin.  An easy move candidate must be at least this much
+  // Easy move margin. An easy move candidate must be at least this much
   // better than the second best move.
   const Value EasyMoveMargin = Value(0x200);
 
-  // Problem margin.  If the score of the first move at iteration N+1 has
+  // Problem margin. If the score of the first move at iteration N+1 has
   // dropped by more than this since iteration N, the boolean variable
   // "Problem" is set to true, which will make the program spend some extra
   // time looking for a better move.
   const Value ProblemMargin = Value(0x28);
 
-  // No problem margin.  If the boolean "Problem" is true, and a new move
+  // No problem margin. If the boolean "Problem" is true, and a new move
   // is found at the root which is less than NoProblemMargin worse than the
   // best move from the previous iteration, Problem is set back to false.
   const Value NoProblemMargin = Value(0x14);
 
-  // Null move margin.  A null move search will not be done if the approximate
+  // Null move margin. A null move search will not be done if the approximate
   // evaluation of the position is more than NullMoveMargin below beta.
   const Value NullMoveMargin = Value(0x300);
 
-  // Pruning criterions.  See the code and comments in ok_to_prune() to
+  // Pruning criterions. See the code and comments in ok_to_prune() to
   // understand their precise meaning.
-  const bool PruneEscapeMoves = false;
+  const bool PruneEscapeMoves    = false;
   const bool PruneDefendingMoves = false;
-  const bool PruneBlockingMoves = false;
-
-  // Use futility pruning?
-  bool UseQSearchFutilityPruning = true;
-  bool UseFutilityPruning = true;
+  const bool PruneBlockingMoves  = false;
 
   // Margins for futility pruning in the quiescence search, and at frontier
-  // and near frontier nodes
-  Value FutilityMarginQS = Value(0x80);
-  Value FutilityMargins[6] = { Value(0x100), Value(0x200), Value(0x250),
-                               Value(0x2A0), Value(0x340), Value(0x3A0) };
+  // and near frontier nodes.
+  const Value FutilityMarginQS = Value(0x80);
 
+  // Remaining depth:                  1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
+  const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270),
+  //                                   4 ply         4.5 ply       5 ply         5.5 ply       6 ply         6.5 ply
+                                      Value(0x2A0), Value(0x2C0), Value(0x340), Value(0x360), Value(0x3A0), Value(0x3C0) };
   // Razoring
-  const bool RazorAtDepthOne = false;
-  Depth RazorDepth = 4*OnePly;
-  Value RazorMargin = Value(0x300);
+  const Depth RazorDepth = 4*OnePly;
 
-  // Last seconds noise filtering (LSN)
-  bool UseLSNFiltering = false;
-  bool looseOnTime = false;
-  int LSNTime = 4 * 1000; // In milliseconds
-  Value LSNValue = Value(0x200);
+  // Remaining depth:                 1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
+  const Value RazorMargins[6]     = { Value(0x180), Value(0x300), Value(0x300), Value(0x3C0), Value(0x3C0), Value(0x3C0) };
 
-  // Extensions.  Array index 0 is used at non-PV nodes, index 1 at PV nodes.
-  Depth CheckExtension[2] = {OnePly, OnePly};
-  Depth SingleReplyExtension[2] = {OnePly / 2, OnePly / 2};
-  Depth PawnPushTo7thExtension[2] = {OnePly / 2, OnePly / 2};
-  Depth PassedPawnExtension[2] = {Depth(0), Depth(0)};
-  Depth PawnEndgameExtension[2] = {OnePly, OnePly};
-  Depth MateThreatExtension[2] = {Depth(0), Depth(0)};
+  // Remaining depth:                 1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
+  const Value RazorApprMargins[6] = { Value(0x520), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
 
-  // Search depth at iteration 1
-  const Depth InitialDepth = OnePly /*+ OnePly/2*/;
+  // The main transposition table
+  TranspositionTable TT;
 
-  // Node counters
-  int NodesSincePoll;
-  int NodesBetweenPolls = 30000;
+
+  /// Variables initialized by UCI options
+
+  // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV nodes
+  int LMRPVMoves, LMRNonPVMoves; // heavy SMP read access for the latter
+
+  // Depth limit for use of dynamic threat detection
+  Depth ThreatDepth; // heavy SMP read access
+
+  // Last seconds noise filtering (LSN)
+  bool UseLSNFiltering;
+  bool looseOnTime = false;
+  int LSNTime; // In milliseconds
+  Value LSNValue;
+
+  // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
+  // There is heavy SMP read access on these arrays
+  Depth CheckExtension[2], SingleReplyExtension[2], PawnPushTo7thExtension[2];
+  Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
 
   // Iteration counters
   int Iteration;
-  BetaCounterType BetaCounter;
+  BetaCounterType BetaCounter; // has per-thread internal data
 
-  // Scores and number of times the best move changed for each iteration:
+  // Scores and number of times the best move changed for each iteration
   IterationInfoType IterationInfo[PLY_MAX_PLUS_2];
   int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
 
   // MultiPV mode
-  int MultiPV = 1;
+  int MultiPV;
 
   // Time managment variables
   int SearchStartTime;
@@ -231,7 +232,7 @@ namespace {
   bool InfiniteSearch;
   bool PonderSearch;
   bool StopOnPonderhit;
-  bool AbortSearch;
+  bool AbortSearch; // heavy SMP read access
   bool Quit;
   bool FailHigh;
   bool FailLow;
@@ -240,17 +241,19 @@ namespace {
   int ExactMaxTime;
 
   // Show current line?
-  bool ShowCurrentLine = false;
+  bool ShowCurrentLine;
 
   // Log file
-  bool UseLogFile = false;
+  bool UseLogFile;
   std::ofstream LogFile;
 
   // MP related variables
-  Depth MinimumSplitDepth = 4*OnePly;
-  int MaxThreadsPerSplitPoint = 4;
+  int ActiveThreads = 1;
+  Depth MinimumSplitDepth;
+  int MaxThreadsPerSplitPoint;
   Thread Threads[THREAD_MAX];
   Lock MPLock;
+  Lock IOLock;
   bool AllThreadsShouldExit = false;
   const int MaxActiveSplitPoints = 8;
   SplitPoint SplitPointStack[THREAD_MAX][MaxActiveSplitPoints];
@@ -263,28 +266,33 @@ namespace {
   HANDLE SitIdleEvent[THREAD_MAX];
 #endif
 
+  // Node counters, used only by thread[0] but try to keep in different
+  // cache lines (64 bytes each) from the heavy SMP read accessed variables.
+  int NodesSincePoll;
+  int NodesBetweenPolls = 30000;
+
 
   /// Functions
 
-  Value id_loop(const Position &pos, Move searchMoves[]);
-  Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta);
-  Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
-  Value search(Position &pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID);
-  Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
-  void sp_search(SplitPoint *sp, int threadID);
-  void sp_search_pv(SplitPoint *sp, int threadID);
+  Value id_loop(const Position& pos, Move searchMoves[]);
+  Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value alpha, Value beta);
+  Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
+  Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID);
+  Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
+  void sp_search(SplitPoint* sp, int threadID);
+  void sp_search_pv(SplitPoint* sp, int threadID);
   void init_node(SearchStack ss[], int ply, int threadID);
   void update_pv(SearchStack ss[], int ply);
-  void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
-  bool connected_moves(const Position &pos, Move m1, Move m2);
+  void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply);
+  bool connected_moves(const Position& pos, Move m1, Move m2);
   bool value_is_mate(Value value);
   bool move_is_killer(Move m, const SearchStack& ss);
-  Depth extension(const Position &pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
-  bool ok_to_do_nullmove(const Position &pos);
-  bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
+  Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
+  bool ok_to_do_nullmove(const Position& pos);
+  bool ok_to_prune(const Position& pos, Move m, Move threat, Depth d, const History& H);
   bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
-  bool ok_to_history(const Position &pos, Move m);
-  void update_history(const Position& pos, Move m, Depth depth, Move movesSearched[], int moveCount);
+  bool ok_to_history(const Position& pos, Move m);
+  void update_history(const Position& pos, Move m, Depth depth, History& H, Move movesSearched[], int moveCount);
   void update_killers(Move m, SearchStack& ss);
 
   bool fail_high_ply_1();
@@ -295,13 +303,13 @@ namespace {
   void print_current_line(SearchStack ss[], int ply, int threadID);
   void wait_for_stop_or_ponderhit();
 
-  void idle_loop(int threadID, SplitPoint *waitSp);
+  void idle_loop(int threadID, SplitPoint* waitSp);
   void init_split_point_stack();
   void destroy_split_point_stack();
   bool thread_should_stop(int threadID);
   bool thread_is_available(int slave, int master);
   bool idle_thread_exists(int master);
-  bool split(const Position &pos, SearchStack *ss, int ply,
+  bool split(const Position& pos, SearchStack* ss, int ply,
              Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
              MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode);
   void wake_sleeping_threads();
@@ -315,53 +323,16 @@ namespace {
 }
 
 
-////
-//// Global variables
-////
-
-// The main transposition table
-TranspositionTable TT = TranspositionTable(TTDefaultSize);
-
-
-// Number of active threads:
-int ActiveThreads = 1;
-
-// Locks.  In principle, there is no need for IOLock to be a global variable,
-// but it could turn out to be useful for debugging.
-Lock IOLock;
-
-History H;  // Should be made local?
-
-// The empty search stack
-SearchStack EmptySearchStack;
-
-
-// SearchStack::init() initializes a search stack. Used at the beginning of a
-// new search from the root.
-void SearchStack::init(int ply) {
-
-  pv[ply] = pv[ply + 1] = MOVE_NONE;
-  currentMove = threatMove = MOVE_NONE;
-  reduction = Depth(0);
-}
-
-void SearchStack::initKillers() {
-
-  mateKiller = MOVE_NONE;
-  for (int i = 0; i < KILLER_MAX; i++)
-      killers[i] = MOVE_NONE;
-}
-
-
 ////
 //// Functions
 ////
 
 /// think() is the external interface to Stockfish's search, and is called when
-/// the program receives the UCI 'go' command.  It initializes various
-/// search-related global variables, and calls root_search()
+/// the program receives the UCI 'go' command. It initializes various
+/// search-related global variables, and calls root_search(). It returns false
+/// when a quit command is received during the search.
 
-void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
+bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
            int time[], int increment[], int movesToGo, int maxDepth,
            int maxNodes, int maxTime, Move searchMoves[]) {
 
@@ -370,15 +341,13 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
   {
       Move bookMove;
       if (get_option_value_string("Book File") != OpeningBook.file_name())
-      {
-          OpeningBook.close();
           OpeningBook.open("book.bin");
-      }
+
       bookMove = OpeningBook.get_move(pos);
       if (bookMove != MOVE_NONE)
       {
           std::cout << "bestmove " << bookMove << std::endl;
-          return;
+          return true;
       }
   }
 
@@ -428,10 +397,9 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
   MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
   MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
 
-  LMRPVMoves     = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
-  LMRNonPVMoves  = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
-  ThreatDepth    = get_option_value_int("Threat Depth") * OnePly;
-  SelectiveDepth = get_option_value_int("Selective Plies") * OnePly;
+  LMRPVMoves    = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
+  LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
+  ThreatDepth   = get_option_value_int("Threat Depth") * OnePly;
 
   Chess960 = get_option_value_bool("UCI_Chess960");
   ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
@@ -439,17 +407,6 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
   if (UseLogFile)
       LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
 
-  UseQSearchFutilityPruning = get_option_value_bool("Futility Pruning (Quiescence Search)");
-  UseFutilityPruning = get_option_value_bool("Futility Pruning (Main Search)");
-
-  FutilityMarginQS = value_from_centipawns(get_option_value_int("Futility Margin (Quiescence Search)"));
-  int fmScale = get_option_value_int("Futility Margin Scale Factor (Main Search)");
-  for (int i = 0; i < 6; i++)
-      FutilityMargins[i] = (FutilityMargins[i] * fmScale) / 100;
-
-  RazorDepth = (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly;
-  RazorMargin = value_from_centipawns(get_option_value_int("Razoring Margin"));
-
   UseLSNFiltering = get_option_value_bool("LSN filtering");
   LSNTime = get_option_value_int("LSN Time Margin (sec)") * 1000;
   LSNValue = value_from_centipawns(get_option_value_int("LSN Value Margin"));
@@ -466,13 +423,13 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
       init_eval(ActiveThreads);
   }
 
-  // Wake up sleeping threads:
+  // Wake up sleeping threads
   wake_sleeping_threads();
 
   for (int i = 1; i < ActiveThreads; i++)
       assert(thread_is_available(i, 0));
 
-  // Set thinking time:
+  // Set thinking time
   int myTime = time[side_to_move];
   int myIncrement = increment[side_to_move];
 
@@ -520,18 +477,17 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
       NodesBetweenPolls = 30000;
 
 
-  // Write information to search log file:
+  // Write information to search log file
   if (UseLogFile)
       LogFile << "Searching: " << pos.to_fen() << std::endl
-              << "infinite: " << infinite
-              << " ponder: " << ponder
-              << " time: " << myTime
+              << "infinite: "  << infinite
+              << " ponder: "   << ponder
+              << " time: "     << myTime
               << " increment: " << myIncrement
               << " moves to go: " << movesToGo << std::endl;
 
 
-  // We're ready to start thinking.  Call the iterative deepening loop
-  // function:
+  // We're ready to start thinking. Call the iterative deepening loop function
   if (!looseOnTime)
   {
       Value v = id_loop(pos, searchMoves);
@@ -551,14 +507,8 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
   if (UseLogFile)
       LogFile.close();
 
-  if (Quit)
-  {
-      OpeningBook.close();
-      stop_threads();
-      quit_eval();
-      exit(0);
-  }
   Idle = true;
+  return !Quit;
 }
 
 
@@ -577,7 +527,7 @@ void init_threads() {
   for (i = 0; i < THREAD_MAX; i++)
       Threads[i].activeSplitPoints = 0;
 
-  // Initialize global locks:
+  // Initialize global locks
   lock_init(&MPLock, NULL);
   lock_init(&IOLock, NULL);
 
@@ -610,13 +560,9 @@ void init_threads() {
       CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
 #endif
 
-      // Wait until the thread has finished launching:
+      // Wait until the thread has finished launching
       while (!Threads[i].running);
   }
-
-  // Init also the empty search stack
-  EmptySearchStack.init(0);
-  EmptySearchStack.initKillers();
 }
 
 
@@ -650,6 +596,22 @@ int64_t nodes_searched() {
 }
 
 
+// SearchStack::init() initializes a search stack. Used at the beginning of a
+// new search from the root.
+void SearchStack::init(int ply) {
+
+  pv[ply] = pv[ply + 1] = MOVE_NONE;
+  currentMove = threatMove = MOVE_NONE;
+  reduction = Depth(0);
+}
+
+void SearchStack::initKillers() {
+
+  mateKiller = MOVE_NONE;
+  for (int i = 0; i < KILLER_MAX; i++)
+      killers[i] = MOVE_NONE;
+}
+
 namespace {
 
   // id_loop() is the main iterative deepening loop.  It calls root_search
@@ -657,7 +619,7 @@ namespace {
   // been consumed, the user stops the search, or the maximum search depth is
   // reached.
 
-  Value id_loop(const Position &pos, Move searchMoves[]) {
+  Value id_loop(const Position& pos, Move searchMoves[]) {
 
     Position p(pos);
     SearchStack ss[PLY_MAX_PLUS_2];
@@ -667,7 +629,9 @@ namespace {
 
     // Initialize
     TT.new_search();
-    H.clear();
+    for (int i = 0; i < THREAD_MAX; i++)
+        Threads[i].H.clear();
+
     for (int i = 0; i < 3; i++)
     {
         ss[i].init(i);
@@ -693,7 +657,7 @@ namespace {
         // Calculate dynamic search window based on previous iterations
         Value alpha, beta;
 
-        if (MultiPV == 1 && Iteration >= 6)
+        if (MultiPV == 1 && Iteration >= 6 && abs(IterationInfo[Iteration - 1].value) < VALUE_KNOWN_WIN)
         {
             int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
             int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
@@ -758,7 +722,7 @@ namespace {
             // Time to stop?
             bool stopSearch = false;
 
-            // Stop search early if there is only a single legal move:
+            // Stop search early if there is only a single legal move
             if (Iteration >= 6 && rml.move_count() == 1)
                 stopSearch = true;
 
@@ -856,7 +820,7 @@ namespace {
   // scheme (perhaps we should try to use this at internal PV nodes, too?)
   // and prints some information to the standard output.
 
-  Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
+  Value root_search(Position& pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
 
     Value oldAlpha = alpha;
     Value value;
@@ -905,6 +869,10 @@ namespace {
 
         if (i < MultiPV)
         {
+            // Aspiration window is disabled in multi-pv case
+            if (MultiPV > 1)
+                alpha = -VALUE_INFINITE;
+
             value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
             // If the value has dropped a lot compared to the last iteration,
             // set the boolean variable Problem to true. This variable is used
@@ -969,7 +937,7 @@ namespace {
                 if (i > 0)
                     BestMoveChangesByIteration[Iteration]++;
 
-                // Print search information to the standard output:
+                // Print search information to the standard output
                 std::cout << "info depth " << Iteration
                           << " score " << value_to_string(value)
                           << " time " << current_search_time()
@@ -1027,7 +995,7 @@ namespace {
 
   // search_pv() is the main search function for PV nodes.
 
-  Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
+  Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta,
                   Depth depth, int ply, int threadID) {
 
     assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
@@ -1063,7 +1031,7 @@ namespace {
 
     // Transposition table lookup. At PV nodes, we don't use the TT for
     // pruning, but only for move ordering.
-    const TTEntry* tte = TT.retrieve(pos);
+    const TTEntry* tte = TT.retrieve(pos.get_key());
     Move ttMove = (tte ? tte->move() : MOVE_NONE);
 
     // Go with internal iterative deepening if we don't have a TT move
@@ -1075,7 +1043,7 @@ namespace {
 
     // Initialize a MovePicker object for the current position, and prepare
     // to search all moves
-    MovePicker mp = MovePicker(pos, true, ttMove, ss[ply], depth);
+    MovePicker mp = MovePicker(pos, ttMove, depth, Threads[threadID].H, &ss[ply]);
 
     Move move, movesSearched[256];
     int moveCount = 0;
@@ -1165,7 +1133,7 @@ namespace {
           }
           // If we are at ply 1, and we are searching the first root move at
           // ply 0, set the 'Problem' variable if the score has dropped a lot
-          // (from the computer's point of view) since the previous iteration:
+          // (from the computer's point of view) since the previous iteration.
           if (   ply == 1
               && Iteration >= 2
               && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
@@ -1186,7 +1154,7 @@ namespace {
     }
 
     // All legal moves have been searched.  A special case: If there were
-    // no legal moves, it must be mate or stalemate:
+    // no legal moves, it must be mate or stalemate.
     if (moveCount == 0)
         return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
 
@@ -1196,7 +1164,7 @@ namespace {
         return bestValue;
 
     if (bestValue <= oldAlpha)
-        TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER);
+        TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
 
     else if (bestValue >= beta)
     {
@@ -1204,13 +1172,13 @@ namespace {
         Move m = ss[ply].pv[ply];
         if (ok_to_history(pos, m)) // Only non capture moves are considered
         {
-            update_history(pos, m, depth, movesSearched, moveCount);
+            update_history(pos, m, depth, Threads[threadID].H, movesSearched, moveCount);
             update_killers(m, ss[ply]);
         }
-        TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
+        TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m);
     }
     else
-        TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply], VALUE_TYPE_EXACT);
+        TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]);
 
     return bestValue;
   }
@@ -1218,7 +1186,7 @@ namespace {
 
   // search() is the search function for zero-width nodes.
 
-  Value search(Position &pos, SearchStack ss[], Value beta, Depth depth,
+  Value search(Position& pos, SearchStack ss[], Value beta, Depth depth,
                int ply, bool allowNullmove, int threadID) {
 
     assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
@@ -1252,7 +1220,7 @@ namespace {
         return beta - 1;
 
     // Transposition table lookup
-    const TTEntry* tte = TT.retrieve(pos);
+    const TTEntry* tte = TT.retrieve(pos.get_key());
     Move ttMove = (tte ? tte->move() : MOVE_NONE);
 
     if (tte && ok_to_use_TT(tte, depth, beta, ply))
@@ -1315,17 +1283,15 @@ namespace {
     }
     // Null move search not allowed, try razoring
     else if (   !value_is_mate(beta)
-             && approximateEval < beta - RazorMargin
              && depth < RazorDepth
-             && (RazorAtDepthOne || depth > OnePly)
+             && approximateEval < beta - RazorApprMargins[int(depth) - 2]
+             && ss[ply - 1].currentMove != MOVE_NULL
              && ttMove == MOVE_NONE
              && !pos.has_pawn_on_7th(pos.side_to_move()))
     {
         Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
-        if (   (v < beta - RazorMargin - RazorMargin / 4)
-            || (depth <= 2*OnePly && v < beta - RazorMargin)
-            || (depth <=   OnePly && v < beta - RazorMargin / 2))
-            return v;
+        if (v < beta - RazorMargins[int(depth) - 2])
+          return v;
     }
 
     // Go with internal iterative deepening if we don't have a TT move
@@ -1337,16 +1303,15 @@ namespace {
     }
 
     // Initialize a MovePicker object for the current position, and prepare
-    // to search all moves:
-    MovePicker mp = MovePicker(pos, false, ttMove, ss[ply], depth);
+    // to search all moves.
+    MovePicker mp = MovePicker(pos, ttMove, depth, Threads[threadID].H, &ss[ply]);
 
     Move move, movesSearched[256];
     int moveCount = 0;
     Value value, bestValue = -VALUE_INFINITE;
     Bitboard dcCandidates = mp.discovered_check_candidates();
     Value futilityValue = VALUE_NONE;
-    bool useFutilityPruning =   UseFutilityPruning
-                             && depth < SelectiveDepth
+    bool useFutilityPruning =   depth < SelectiveDepth
                              && !isCheck;
 
     // Loop through all legal moves until no moves remain or a beta cutoff
@@ -1376,16 +1341,15 @@ namespace {
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)
-              && ok_to_prune(pos, move, ss[ply].threatMove, depth))
+              && ok_to_prune(pos, move, ss[ply].threatMove, depth, Threads[threadID].H))
               continue;
 
           // Value based pruning
-          if (depth < 7 * OnePly && approximateEval < beta)
+          if (approximateEval < beta)
           {
               if (futilityValue == VALUE_NONE)
                   futilityValue =  evaluate(pos, ei, threadID)
-                                 + FutilityMargins[int(depth)/2 - 1]
-                                 + 32 * (depth & 1);
+                                 + FutilityMargins[int(depth) - 2];
 
               if (futilityValue < beta)
               {
@@ -1460,17 +1424,17 @@ namespace {
         return bestValue;
 
     if (bestValue < beta)
-        TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER);
+        TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
     else
     {
         BetaCounter.add(pos.side_to_move(), depth, threadID);
         Move m = ss[ply].pv[ply];
         if (ok_to_history(pos, m)) // Only non capture moves are considered
         {
-            update_history(pos, m, depth, movesSearched, moveCount);
+            update_history(pos, m, depth, Threads[threadID].H, movesSearched, moveCount);
             update_killers(m, ss[ply]);
         }
-        TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
+        TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m);
     }
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
@@ -1483,7 +1447,7 @@ namespace {
   // search function when the remaining depth is zero (or, to be more precise,
   // less than OnePly).
 
-  Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
+  Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta,
                 Depth depth, int ply, int threadID) {
 
     assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
@@ -1508,7 +1472,7 @@ namespace {
     bool pvNode = (beta - alpha != 1);
     if (!pvNode)
     {
-        tte = TT.retrieve(pos);
+        tte = TT.retrieve(pos.get_key());
         if (tte && ok_to_use_TT(tte, depth, beta, ply))
         {
             assert(tte->type() != VALUE_TYPE_EVAL);
@@ -1516,6 +1480,7 @@ namespace {
             return value_from_tt(tte->value(), ply);
         }
     }
+    Move ttMove = (tte ? tte->move() : MOVE_NONE);
 
     // Evaluate the position statically
     EvalInfo ei;
@@ -1548,7 +1513,7 @@ namespace {
     {
         // Store the score to avoid a future costly evaluation() call
         if (!isCheck && !tte && ei.futilityMargin == 0)
-            TT.store(pos, value_to_tt(bestValue, ply), Depth(-127*OnePly), MOVE_NONE, VALUE_TYPE_EVAL);
+            TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EVAL, Depth(-127*OnePly), MOVE_NONE);
 
         return bestValue;
     }
@@ -1559,7 +1524,7 @@ namespace {
     // Initialize a MovePicker object for the current position, and prepare
     // to search the moves.  Because the depth is <= 0 here, only captures,
     // queen promotions and checks (only if depth == 0) will be generated.
-    MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth);
+    MovePicker mp = MovePicker(pos, ttMove, depth, Threads[threadID].H);
     Move move;
     int moveCount = 0;
     Bitboard dcCandidates = mp.discovered_check_candidates();
@@ -1577,8 +1542,7 @@ namespace {
       ss[ply].currentMove = move;
 
       // Futility pruning
-      if (    UseQSearchFutilityPruning
-          &&  enoughMaterial
+      if (   enoughMaterial
           && !isCheck
           && !pvNode
           && !move_promotion(move)
@@ -1629,29 +1593,27 @@ namespace {
     }
 
     // All legal moves have been searched.  A special case: If we're in check
-    // and no legal moves were found, it is checkmate:
+    // and no legal moves were found, it is checkmate.
     if (pos.is_check() && moveCount == 0) // Mate!
         return value_mated_in(ply);
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
     // Update transposition table
+    Move m = ss[ply].pv[ply];
     if (!pvNode)
     {
         Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
         if (bestValue < beta)
-            TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER);
+            TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, d, MOVE_NONE);
         else
-            TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_LOWER);
+            TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, m);
     }
 
     // Update killers only for good check moves
-    Move m = ss[ply].currentMove;
     if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
-    {
-        // Wrong to update history when depth is <= 0
         update_killers(m, ss[ply]);
-    }
+
     return bestValue;
   }
 
@@ -1664,18 +1626,17 @@ namespace {
   // also don't need to store anything to the hash table here:  This is taken
   // care of after we return from the split point.
 
-  void sp_search(SplitPoint *sp, int threadID) {
+  void sp_search(SplitPoint* sp, int threadID) {
 
     assert(threadID >= 0 && threadID < ActiveThreads);
     assert(ActiveThreads > 1);
 
     Position pos = Position(sp->pos);
-    SearchStack *ss = sp->sstack[threadID];
+    SearchStack* ss = sp->sstack[threadID];
     Value value;
     Move move;
     bool isCheck = pos.is_check();
-    bool useFutilityPruning =    UseFutilityPruning
-                              && sp->depth < SelectiveDepth
+    bool useFutilityPruning =     sp->depth < SelectiveDepth
                               && !isCheck;
 
     while (    sp->bestValue < sp->beta
@@ -1704,7 +1665,7 @@ namespace {
           && !moveIsCapture
           && !move_promotion(move)
           &&  moveCount >= 2 + int(sp->depth)
-          &&  ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
+          &&  ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth, Threads[threadID].H))
         continue;
 
       // Make and search the move.
@@ -1759,7 +1720,7 @@ namespace {
     lock_grab(&(sp->lock));
 
     // If this is the master thread and we have been asked to stop because of
-    // a beta cutoff higher up in the tree, stop all slave threads:
+    // a beta cutoff higher up in the tree, stop all slave threads.
     if (sp->master == threadID && thread_should_stop(threadID))
         for (int i = 0; i < ActiveThreads; i++)
             if (sp->slaves[i])
@@ -1777,16 +1738,16 @@ namespace {
   // the normal search_pv() function, but simpler.  Because we have already
   // probed the hash table and searched the first move before splitting, we
   // don't have to repeat all this work in sp_search_pv().  We also don't
-  // need to store anything to the hash table here:  This is taken care of
+  // need to store anything to the hash table here: This is taken care of
   // after we return from the split point.
 
-  void sp_search_pv(SplitPoint *sp, int threadID) {
+  void sp_search_pv(SplitPoint* sp, int threadID) {
 
     assert(threadID >= 0 && threadID < ActiveThreads);
     assert(ActiveThreads > 1);
 
     Position pos = Position(sp->pos);
-    SearchStack *ss = sp->sstack[threadID];
+    SearchStack* ss = sp->sstack[threadID];
     Value value;
     Move move;
 
@@ -1838,7 +1799,7 @@ namespace {
           {
               // When the search fails high at ply 1 while searching the first
               // move at the root, set the flag failHighPly1.  This is used for
-              // time managment:  We don't want to stop the search early in
+              // time managment: We don't want to stop the search early in
               // such cases, because resolving the fail high at ply 1 could
               // result in a big drop in score at the root.
               if (sp->ply == 1 && RootMoveNumber == 1)
@@ -1867,10 +1828,10 @@ namespace {
               if (value == value_mate_in(sp->ply + 1))
                   ss[sp->ply].mateKiller = move;
 
-              if(value >= sp->beta)
+              if (value >= sp->beta)
               {
-                  for(int i = 0; i < ActiveThreads; i++)
-                      if(i != threadID && (i == sp->master || sp->slaves[i]))
+                  for (int i = 0; i < ActiveThreads; i++)
+                      if (i != threadID && (i == sp->master || sp->slaves[i]))
                           Threads[i].stop = true;
 
                   sp->finished = true;
@@ -1909,13 +1870,13 @@ namespace {
   void BetaCounterType::clear() {
 
     for (int i = 0; i < THREAD_MAX; i++)
-        hits[i][WHITE] = hits[i][BLACK] = 0ULL;
+        Threads[i].betaCutOffs[WHITE] = Threads[i].betaCutOffs[BLACK] = 0ULL;
   }
 
   void BetaCounterType::add(Color us, Depth d, int threadID) {
 
     // Weighted count based on depth
-    hits[threadID][us] += int(d);
+    Threads[threadID].betaCutOffs[us] += unsigned(d);
   }
 
   void BetaCounterType::read(Color us, int64_t& our, int64_t& their) {
@@ -1923,8 +1884,8 @@ namespace {
     our = their = 0UL;
     for (int i = 0; i < THREAD_MAX; i++)
     {
-        our += hits[i][us];
-        their += hits[i][opposite_color(us)];
+        our += Threads[i].betaCutOffs[us];
+        their += Threads[i].betaCutOffs[opposite_color(us)];
     }
   }
 
@@ -1934,7 +1895,7 @@ namespace {
   // Constructor
 
   RootMove::RootMove() {
-    nodes = cumulativeNodes = 0ULL;
+    nodes = cumulativeNodes = ourBeta = theirBeta = 0ULL;
   }
 
   // RootMove::operator<() is the comparison function used when
@@ -1970,22 +1931,20 @@ namespace {
         for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
             includeMove = (searchMoves[k] == mlist[i].move);
 
-        if (includeMove)
-        {
-            // Find a quick score for the move
-            StateInfo st;
-            SearchStack ss[PLY_MAX_PLUS_2];
-
-            moves[count].move = mlist[i].move;
-            moves[count].nodes = 0ULL;
-            pos.do_move(moves[count].move, st);
-            moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE,
-                                          Depth(0), 1, 0);
-            pos.undo_move(moves[count].move);
-            moves[count].pv[0] = moves[i].move;
-            moves[count].pv[1] = MOVE_NONE; // FIXME
-            count++;
-        }
+        if (!includeMove)
+            continue;
+
+        // Find a quick score for the move
+        StateInfo st;
+        SearchStack ss[PLY_MAX_PLUS_2];
+
+        moves[count].move = mlist[i].move;
+        pos.do_move(moves[count].move, st);
+        moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
+        pos.undo_move(moves[count].move);
+        moves[count].pv[0] = moves[count].move;
+        moves[count].pv[1] = MOVE_NONE; // FIXME
+        count++;
     }
     sort();
   }
@@ -2090,24 +2049,26 @@ namespace {
   // for user input and checks whether it is time to stop the search.
 
   void init_node(SearchStack ss[], int ply, int threadID) {
+
     assert(ply >= 0 && ply < PLY_MAX);
     assert(threadID >= 0 && threadID < ActiveThreads);
 
     Threads[threadID].nodes++;
 
-    if(threadID == 0) {
-      NodesSincePoll++;
-      if(NodesSincePoll >= NodesBetweenPolls) {
-        poll();
-        NodesSincePoll = 0;
-      }
+    if (threadID == 0)
+    {
+        NodesSincePoll++;
+        if (NodesSincePoll >= NodesBetweenPolls)
+        {
+            poll();
+            NodesSincePoll = 0;
+        }
     }
-
     ss[ply].init(ply);
     ss[ply+2].initKillers();
 
-    if(Threads[threadID].printCurrentLine)
-      print_current_line(ss, ply, threadID);
+    if (Threads[threadID].printCurrentLine)
+        print_current_line(ss, ply, threadID);
   }
 
 
@@ -2130,7 +2091,7 @@ namespace {
   // difference between the two functions is that sp_update_pv also updates
   // the PV at the parent node.
 
-  void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply) {
+  void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply) {
     assert(ply >= 0 && ply < PLY_MAX);
 
     ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
@@ -2147,62 +2108,62 @@ namespace {
   // assumed to be the move that was made to reach the current position, while
   // the second move is assumed to be a move from the current position.
 
-  bool connected_moves(const Position &pos, Move m1, Move m2) {
+  bool connected_moves(const Position& pos, Move m1, Move m2) {
     Square f1, t1, f2, t2;
 
     assert(move_is_ok(m1));
     assert(move_is_ok(m2));
 
-    if(m2 == MOVE_NONE)
-      return false;
+    if (m2 == MOVE_NONE)
+        return false;
 
-    // Case 1: The moving piece is the same in both moves.
+    // Case 1: The moving piece is the same in both moves
     f2 = move_from(m2);
     t1 = move_to(m1);
-    if(f2 == t1)
-      return true;
+    if (f2 == t1)
+        return true;
 
-    // Case 2: The destination square for m2 was vacated by m1.
+    // Case 2: The destination square for m2 was vacated by m1
     t2 = move_to(m2);
     f1 = move_from(m1);
-    if(t2 == f1)
-      return true;
+    if (t2 == f1)
+        return true;
 
-    // Case 3: Moving through the vacated square:
-    if(piece_is_slider(pos.piece_on(f2)) &&
-       bit_is_set(squares_between(f2, t2), f1))
+    // Case 3: Moving through the vacated square
+    if (   piece_is_slider(pos.piece_on(f2))
+        && bit_is_set(squares_between(f2, t2), f1))
       return true;
 
-    // Case 4: The destination square for m2 is attacked by the moving piece
-    // in m1:
-    if(pos.piece_attacks_square(pos.piece_on(t1), t1, t2))
-      return true;
+    // Case 4: The destination square for m2 is attacked by the moving piece in m1
+    if (pos.piece_attacks_square(pos.piece_on(t1), t1, t2))
+        return true;
 
-    // Case 5: Discovered check, checking piece is the piece moved in m1:
-    if(piece_is_slider(pos.piece_on(t1)) &&
-       bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())),
-                  f2) &&
-       !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())),
-                   t2)) {
-      Bitboard occ = pos.occupied_squares();
-      Color us = pos.side_to_move();
-      Square ksq = pos.king_square(us);
-      clear_bit(&occ, f2);
-      if(pos.type_of_piece_on(t1) == BISHOP) {
-        if(bit_is_set(bishop_attacks_bb(ksq, occ), t1))
-          return true;
-      }
-      else if(pos.type_of_piece_on(t1) == ROOK) {
-        if(bit_is_set(rook_attacks_bb(ksq, occ), t1))
-          return true;
-      }
-      else {
-        assert(pos.type_of_piece_on(t1) == QUEEN);
-        if(bit_is_set(queen_attacks_bb(ksq, occ), t1))
-          return true;
-      }
+    // Case 5: Discovered check, checking piece is the piece moved in m1
+    if (   piece_is_slider(pos.piece_on(t1))
+        && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
+        && !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())), t2))
+    {
+        Bitboard occ = pos.occupied_squares();
+        Color us = pos.side_to_move();
+        Square ksq = pos.king_square(us);
+        clear_bit(&occ, f2);
+        if (pos.type_of_piece_on(t1) == BISHOP)
+        {
+            if (bit_is_set(bishop_attacks_bb(ksq, occ), t1))
+                return true;
+        }
+        else if (pos.type_of_piece_on(t1) == ROOK)
+        {
+            if (bit_is_set(rook_attacks_bb(ksq, occ), t1))
+                return true;
+        }
+        else
+        {
+            assert(pos.type_of_piece_on(t1) == QUEEN);
+            if (bit_is_set(queen_attacks_bb(ksq, occ), t1))
+                return true;
+        }
     }
-
     return false;
   }
 
@@ -2303,10 +2264,9 @@ namespace {
   // probably a good idea to avoid null moves in at least some more
   // complicated endgames, e.g. KQ vs KR.  FIXME
 
-  bool ok_to_do_nullmove(const Position &pos) {
-    if(pos.non_pawn_material(pos.side_to_move()) == Value(0))
-      return false;
-    return true;
+  bool ok_to_do_nullmove(const Position& pos) {
+
+    return pos.non_pawn_material(pos.side_to_move()) != Value(0);
   }
 
 
@@ -2314,8 +2274,7 @@ namespace {
   // non-tactical moves late in the move list close to the leaves are
   // candidates for pruning.
 
-  bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d) {
-    Square mfrom, mto, tfrom, tto;
+  bool ok_to_prune(const Position& pos, Move m, Move threat, Depth d, const History& H) {
 
     assert(move_is_ok(m));
     assert(threat == MOVE_NONE || move_is_ok(threat));
@@ -2325,12 +2284,14 @@ namespace {
     assert(!pos.move_is_passed_pawn_push(m));
     assert(d >= OnePly);
 
+    Square mfrom, mto, tfrom, tto;
+
     mfrom = move_from(m);
     mto = move_to(m);
     tfrom = move_from(threat);
     tto = move_to(threat);
 
-    // Case 1: Castling moves are never pruned.
+    // Case 1: Castling moves are never pruned
     if (move_is_castle(m))
         return false;
 
@@ -2346,10 +2307,10 @@ namespace {
         && (   pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
             || pos.type_of_piece_on(tfrom) == KING)
         && pos.move_attacks_square(m, tto))
-      return false;
+        return false;
 
-    // Case 4: Don't prune moves with good history.
-    if (!H.ok_to_prune(pos.piece_on(move_from(m)), m, d))
+    // Case 4: Don't prune moves with good history
+    if (!H.ok_to_prune(pos.piece_on(mfrom), mto, d))
         return false;
 
     // Case 5: If the moving piece in the threatened move is a slider, don't
@@ -2359,7 +2320,7 @@ namespace {
         && piece_is_slider(pos.piece_on(tfrom))
         && bit_is_set(squares_between(tfrom, tto), mto)
         && pos.see(m) >= 0)
-            return false;
+        return false;
 
     return true;
   }
@@ -2393,16 +2354,16 @@ namespace {
   // update_history() registers a good move that produced a beta-cutoff
   // in history and marks as failures all the other moves of that ply.
 
-  void update_history(const Position& pos, Move m, Depth depth,
+  void update_history(const Position& pos, Move m, Depth depth, History& H,
                       Move movesSearched[], int moveCount) {
 
-    H.success(pos.piece_on(move_from(m)), m, depth);
+    H.success(pos.piece_on(move_from(m)), move_to(m), depth);
 
     for (int i = 0; i < moveCount - 1; i++)
     {
         assert(m != movesSearched[i]);
         if (ok_to_history(pos, movesSearched[i]))
-            H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]);
+            H.failure(pos.piece_on(move_from(movesSearched[i])), move_to(movesSearched[i]));
     }
   }
 
@@ -2426,9 +2387,11 @@ namespace {
   // is used for time managment.
 
   bool fail_high_ply_1() {
+
     for(int i = 0; i < ActiveThreads; i++)
-      if(Threads[i].failHighPly1)
-        return true;
+        if (Threads[i].failHighPly1)
+            return true;
+
     return false;
   }
 
@@ -2471,13 +2434,14 @@ namespace {
             AbortSearch = true;
             PonderSearch = false;
             Quit = true;
+            return;
         }
-        else if(command == "stop")
+        else if (command == "stop")
         {
             AbortSearch = true;
             PonderSearch = false;
         }
-        else if(command == "ponderhit")
+        else if (command == "ponderhit")
             ponderhit();
     }
     // Print search information
@@ -2526,9 +2490,10 @@ namespace {
   // it correctly predicted the opponent's move.
 
   void ponderhit() {
+
     int t = current_search_time();
     PonderSearch = false;
-    if(Iteration >= 3 &&
+    if (Iteration >= 3 &&
        (!InfiniteSearch && (StopOnPonderhit ||
                             t > AbsoluteMaxSearchTime ||
                             (RootMoveNumber == 1 &&
@@ -2543,20 +2508,23 @@ namespace {
   // thread.  Called when the UCI option UCI_ShowCurrLine is 'true'.
 
   void print_current_line(SearchStack ss[], int ply, int threadID) {
+
     assert(ply >= 0 && ply < PLY_MAX);
     assert(threadID >= 0 && threadID < ActiveThreads);
 
-    if(!Threads[threadID].idle) {
-      lock_grab(&IOLock);
-      std::cout << "info currline " << (threadID + 1);
-      for(int p = 0; p < ply; p++)
-        std::cout << " " << ss[p].currentMove;
-      std::cout << std::endl;
-      lock_release(&IOLock);
+    if (!Threads[threadID].idle)
+    {
+        lock_grab(&IOLock);
+        std::cout << "info currline " << (threadID + 1);
+        for (int p = 0; p < ply; p++)
+            std::cout << " " << ss[p].currentMove;
+
+        std::cout << std::endl;
+        lock_release(&IOLock);
     }
     Threads[threadID].printCurrentLine = false;
-    if(threadID + 1 < ActiveThreads)
-      Threads[threadID + 1].printCurrentLine = true;
+    if (threadID + 1 < ActiveThreads)
+        Threads[threadID + 1].printCurrentLine = true;
   }
 
 
@@ -2568,20 +2536,21 @@ namespace {
   // after which the bestmove and pondermove will be printed (in id_loop()).
 
   void wait_for_stop_or_ponderhit() {
+
     std::string command;
 
-    while(true) {
-      if(!std::getline(std::cin, command))
-        command = "quit";
-
-      if(command == "quit") {
-        OpeningBook.close();
-        stop_threads();
-        quit_eval();
-        exit(0);
-      }
-      else if(command == "ponderhit" || command == "stop")
-        break;
+    while (true)
+    {
+        if (!std::getline(std::cin, command))
+            command = "quit";
+
+        if (command == "quit")
+        {
+            Quit = true;
+            break;
+        }
+        else if (command == "ponderhit" || command == "stop")
+            break;
     }
   }
 
@@ -2590,7 +2559,7 @@ namespace {
   // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
   // object for which the current thread is the master.
 
-  void idle_loop(int threadID, SplitPoint *waitSp) {
+  void idle_loop(int threadID, SplitPoint* waitSp) {
     assert(threadID >= 0 && threadID < THREAD_MAX);
 
     Threads[threadID].running = true;
@@ -2612,7 +2581,7 @@ namespace {
 #endif
       }
 
-      // If this thread has been assigned work, launch a search:
+      // If this thread has been assigned work, launch a search
       if(Threads[threadID].workIsWaiting) {
         Threads[threadID].workIsWaiting = false;
         if(Threads[threadID].splitPoint->pvNode)
@@ -2623,7 +2592,7 @@ namespace {
       }
 
       // If this thread is the master of a split point and all threads have
-      // finished their work at this split point, return from the idle loop:
+      // finished their work at this split point, return from the idle loop.
       if(waitSp != NULL && waitSp->cpus == 0)
         return;
     }
@@ -2662,7 +2631,7 @@ namespace {
   bool thread_should_stop(int threadID) {
     assert(threadID >= 0 && threadID < ActiveThreads);
 
-    SplitPoint *sp;
+    SplitPoint* sp;
 
     if(Threads[threadID].stop)
       return true;
@@ -2735,9 +2704,9 @@ namespace {
   // threads have returned from sp_search_pv (or, equivalently, when
   // splitPoint->cpus becomes 0), split() returns true.
 
-  bool split(const Position &p, SearchStack *sstck, int ply,
-             Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
-             MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) {
+  bool split(const Position& p, SearchStack* sstck, int ply,
+             Value* alpha, Value* beta, Value* bestValue, Depth depth, int* moves,
+             MovePicker* mp, Bitboard dcCandidates, int master, bool pvNode) {
 
     assert(p.is_ok());
     assert(sstck != NULL);
@@ -2749,24 +2718,24 @@ namespace {
     assert(master >= 0 && master < ActiveThreads);
     assert(ActiveThreads > 1);
 
-    SplitPoint *splitPoint;
+    SplitPoint* splitPoint;
     int i;
 
     lock_grab(&MPLock);
 
     // If no other thread is available to help us, or if we have too many
-    // active split points, don't split:
+    // active split points, don't split.
     if(!idle_thread_exists(master) ||
        Threads[master].activeSplitPoints >= MaxActiveSplitPoints) {
       lock_release(&MPLock);
       return false;
     }
 
-    // Pick the next available split point object from the split point stack:
+    // Pick the next available split point object from the split point stack
     splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
     Threads[master].activeSplitPoints++;
 
-    // Initialize the split point object:
+    // Initialize the split point object
     splitPoint->parent = Threads[master].splitPoint;
     splitPoint->finished = false;
     splitPoint->ply = ply;
@@ -2785,11 +2754,11 @@ namespace {
     for(i = 0; i < ActiveThreads; i++)
       splitPoint->slaves[i] = 0;
 
-    // Copy the current position and the search stack to the master thread:
+    // Copy the current position and the search stack to the master thread
     memcpy(splitPoint->sstack[master], sstck, (ply+1)*sizeof(SearchStack));
     Threads[master].splitPoint = splitPoint;
 
-    // Make copies of the current position and search stack for each thread:
+    // Make copies of the current position and search stack for each thread
     for(i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint;
         i++)
       if(thread_is_available(i, master)) {
@@ -2819,7 +2788,7 @@ namespace {
     idle_loop(master, splitPoint);
 
     // We have returned from the idle loop, which means that all threads are
-    // finished.  Update alpha, beta and bestvalue, and return:
+    // finished. Update alpha, beta and bestvalue, and return.
     lock_grab(&MPLock);
     if(pvNode) *alpha = splitPoint->alpha;
     *beta = splitPoint->beta;