X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=72530f2e94a1a324ef0c5818a2677c0aed5d543b;hp=ba80ccdfde93ba1ab4ec97ed68d74e69fe929613;hb=db46602b1ff41ff5ef1c41ed04829dc964722b25;hpb=c02613860a3836bb85da25ae2fed9f1351ba27a5

diff --git a/src/search.cpp b/src/search.cpp
index ba80ccdf..72530f2e 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -125,9 +125,6 @@ namespace {
   const bool UseIIDAtPVNodes = true;
   const bool UseIIDAtNonPVNodes = false;
 
-  // Use null move driven internal iterative deepening?
-  bool UseNullDrivenIID = 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.
@@ -196,7 +193,6 @@ namespace {
 
   // Iteration counters
   int Iteration;
-  bool LastIterations;
   BetaCounterType BetaCounter;
 
   // Scores and number of times the best move changed for each iteration:
@@ -210,7 +206,7 @@ namespace {
   int SearchStartTime;
   int MaxNodes, MaxDepth;
   int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
-  Move BestRootMove, PonderMove, EasyMove;
+  Move EasyMove;
   int RootMoveNumber;
   bool InfiniteSearch;
   bool PonderSearch;
@@ -259,8 +255,6 @@ namespace {
                 Depth depth, int ply, int threadID);
   void sp_search(SplitPoint *sp, int threadID);
   void sp_search_pv(SplitPoint *sp, int threadID);
-  void init_search_stack(SearchStack& ss);
-  void init_search_stack(SearchStack ss[]);
   void init_node(const Position &pos, SearchStack ss[], int ply, int threadID);
   void update_pv(SearchStack ss[], int ply);
   void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
@@ -324,6 +318,24 @@ History H;  // Should be made local?
 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);
+  currentMoveCaptureValue = Value(0);
+}
+
+void SearchStack::initKillers() {
+
+  mateKiller = MOVE_NONE;
+  for (int i = 0; i < KILLER_MAX; i++)
+      killers[i] = MOVE_NONE;
+}
+
+
 ////
 //// Functions
 ////
@@ -356,8 +368,6 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
   // Initialize global search variables
   Idle = false;
   SearchStartTime = get_system_time();
-  BestRootMove = MOVE_NONE;
-  PonderMove = MOVE_NONE;
   EasyMove = MOVE_NONE;
   for (int i = 0; i < THREAD_MAX; i++)
   {
@@ -411,7 +421,6 @@ 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);
 
-  UseNullDrivenIID = get_option_value_bool("Null driven IID");
   UseQSearchFutilityPruning = get_option_value_bool("Futility Pruning (Quiescence Search)");
   UseFutilityPruning = get_option_value_bool("Futility Pruning (Main Search)");
 
@@ -588,7 +597,8 @@ void init_threads() {
   }
 
   // Init also the empty search stack
-  init_search_stack(EmptySearchStack);
+  EmptySearchStack.init(0);
+  EmptySearchStack.initKillers();
 }
 
 
@@ -640,12 +650,14 @@ namespace {
     // Initialize
     TT.new_search();
     H.clear();
-    init_search_stack(ss);
-
+    for (int i = 0; i < 3; i++)
+    {
+        ss[i].init(i);
+        ss[i].initKillers();
+    }
     ValueByIteration[0] = Value(0);
     ValueByIteration[1] = rml.get_move_score(0);
     Iteration = 1;
-    LastIterations = false;
 
     EasyMove = rml.scan_for_easy_move();
 
@@ -700,9 +712,6 @@ namespace {
                 ExtraSearchTime = BestMoveChangesByIteration[Iteration]   * (MaxSearchTime / 2)
                                 + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
 
-            // Try to guess if the current iteration is the last one or the last two
-            LastIterations = (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*58) / 128);
-
             // Stop search if most of MaxSearchTime is consumed at the end of the
             // iteration.  We probably don't have enough time to search the first
             // move at the next iteration anyway.
@@ -739,6 +748,11 @@ namespace {
                   << " hashfull " << TT.full() << std::endl;
 
     // Print the best move and the ponder move to the standard output
+    if (ss[0].pv[0] == MOVE_NONE)
+    {
+        ss[0].pv[0] = rml.get_move(0);
+        ss[0].pv[1] = MOVE_NONE;
+    }
     std::cout << "bestmove " << ss[0].pv[0];
     if (ss[0].pv[1] != MOVE_NONE)
         std::cout << " ponder " << ss[0].pv[1];
@@ -1171,7 +1185,6 @@ namespace {
 
     Value approximateEval = quick_evaluate(pos);
     bool mateThreat = false;
-    bool nullDrivenIID = false;
     bool isCheck = pos.is_check();
 
     // Null move search
@@ -1190,19 +1203,6 @@ namespace {
 
         Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
 
-        // Check for a null capture artifact, if the value without the null capture
-        // is above beta then mark the node as a suspicious failed low. We will verify
-        // later if we are really under threat.
-        if (   UseNullDrivenIID
-            && nullValue < beta
-            && depth > 6 * OnePly
-            &&!value_is_mate(nullValue)
-            && ttMove == MOVE_NONE
-            && ss[ply + 1].currentMove != MOVE_NONE
-            && pos.move_is_capture(ss[ply + 1].currentMove)
-            && pos.see(ss[ply + 1].currentMove) + nullValue >= beta)
-            nullDrivenIID = true;
-
         pos.undo_null_move();
 
         if (value_is_mate(nullValue))
@@ -1226,10 +1226,8 @@ namespace {
             // low score (which will cause the reduced move to fail high in the
             // parent node, which will trigger a re-search with full depth).
             if (nullValue == value_mated_in(ply + 2))
-            {
                 mateThreat = true;
-                nullDrivenIID = false;
-            }
+
             ss[ply].threatMove = ss[ply + 1].currentMove;
             if (   depth < ThreatDepth
                 && ss[ply - 1].reduction
@@ -1247,8 +1245,8 @@ namespace {
     {
         Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
         if (   (v < beta - RazorMargin - RazorMargin / 4)
-            || (depth < 3*OnePly && v < beta - RazorMargin)
-            || (depth < 2*OnePly && v < beta - RazorMargin / 2))
+            || (depth <= 2*OnePly && v < beta - RazorMargin)
+            || (depth <=   OnePly && v < beta - RazorMargin / 2))
             return v;
     }
 
@@ -1259,22 +1257,6 @@ namespace {
         search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
         ttMove = ss[ply].pv[ply];
     }
-    else if (nullDrivenIID)
-    {
-        // The null move failed low due to a suspicious capture. Perhaps we
-        // are facing a null capture artifact due to the side to move change
-        // and this position should fail high. So do a normal search with a
-        // reduced depth to get a good ttMove to use in the following full
-        // depth search.
-        Move tm = ss[ply].threatMove;
-
-        assert(tm != MOVE_NONE);
-        assert(ttMove == MOVE_NONE);
-
-        search(pos, ss, beta, depth/2, ply, false, threadID);
-        ttMove = ss[ply].pv[ply];
-        ss[ply].threatMove = tm;
-    }
 
     // Initialize a MovePicker object for the current position, and prepare
     // to search all moves:
@@ -1350,8 +1332,11 @@ namespace {
           && !move_is_castle(move)
           && !move_is_killer(move, ss[ply]))
       {
-          ss[ply].reduction = OnePly;
-          value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true, threadID);
+          // LMR dynamic reduction
+          Depth R = (moveCount >= 2 * LMRNonPVMoves && depth > 7*OnePly ? 2*OnePly : OnePly);
+
+          ss[ply].reduction = R;
+          value = -search(pos, ss, -(beta-1), newDepth-R, ply+1, true, threadID);
       }
       else
         value = beta; // Just to trigger next condition
@@ -1412,6 +1397,9 @@ namespace {
         }
         TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
     }
+
+    assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
+
     return bestValue;
   }
 
@@ -1440,10 +1428,14 @@ namespace {
     if (pos.is_draw())
         return VALUE_DRAW;
 
-    // Transposition table lookup
-    const TTEntry* tte = TT.retrieve(pos);
-    if (tte && ok_to_use_TT(tte, depth, beta, ply))
-        return value_from_tt(tte->value(), ply);
+    // Transposition table lookup, only when not in PV
+    bool pvNode = (beta - alpha != 1);
+    if (!pvNode)
+    {
+        const TTEntry* tte = TT.retrieve(pos);
+        if (tte && ok_to_use_TT(tte, depth, beta, ply))
+            return value_from_tt(tte->value(), ply);
+    }
 
     // Evaluate the position statically
     EvalInfo ei;
@@ -1466,7 +1458,6 @@ 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.
-    bool pvNode = (beta - alpha != 1);
     MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth, isCheck ? NULL : &ei);
     Move move;
     int moveCount = 0;
@@ -1990,34 +1981,6 @@ namespace {
   }
 
 
-  // init_search_stack() initializes a search stack at the beginning of a
-  // new search from the root.
-  void init_search_stack(SearchStack& ss) {
-
-    ss.pv[0] = MOVE_NONE;
-    ss.pv[1] = MOVE_NONE;
-    ss.currentMove = MOVE_NONE;
-    ss.threatMove = MOVE_NONE;
-    ss.reduction = Depth(0);
-    for (int j = 0; j < KILLER_MAX; j++)
-        ss.killers[j] = MOVE_NONE;
-  }
-
-  void init_search_stack(SearchStack ss[]) {
-
-    for (int i = 0; i < 3; i++)
-    {
-        ss[i].pv[i] = MOVE_NONE;
-        ss[i].pv[i+1] = MOVE_NONE;
-        ss[i].currentMove = MOVE_NONE;
-        ss[i].threatMove = MOVE_NONE;
-        ss[i].reduction = Depth(0);
-        for (int j = 0; j < KILLER_MAX; j++)
-            ss[i].killers[j] = MOVE_NONE;
-    }
-  }
-
-
   // init_node() is called at the beginning of all the search functions
   // (search(), search_pv(), qsearch(), and so on) and initializes the search
   // stack object corresponding to the current node.  Once every
@@ -2037,13 +2000,9 @@ namespace {
         NodesSincePoll = 0;
       }
     }
-    ss[ply].pv[ply] = ss[ply].pv[ply+1] = ss[ply].currentMove = MOVE_NONE;
-    ss[ply+2].mateKiller = MOVE_NONE;
-    ss[ply].threatMove = MOVE_NONE;
-    ss[ply].reduction = Depth(0);
-    ss[ply].currentMoveCaptureValue = Value(0);
-    for (int j = 0; j < KILLER_MAX; j++)
-        ss[ply+2].killers[j] = MOVE_NONE;
+
+    ss[ply].init(ply);
+    ss[ply+2].initKillers();
 
     if(Threads[threadID].printCurrentLine)
       print_current_line(ss, ply, threadID);
@@ -2453,7 +2412,7 @@ namespace {
                      || (  !FailHigh && !fail_high_ply_1() && !Problem
                          && t > 6*(MaxSearchTime + ExtraSearchTime));
 
-    if (   (Iteration >= 2 && (!InfiniteSearch && overTime))
+    if (   (Iteration >= 3 && (!InfiniteSearch && overTime))
         || (ExactMaxTime && t >= ExactMaxTime)
         || (Iteration >= 3 && MaxNodes && nodes_searched() >= MaxNodes))
         AbortSearch = true;
@@ -2467,7 +2426,7 @@ namespace {
   void ponderhit() {
     int t = current_search_time();
     PonderSearch = false;
-    if(Iteration >= 2 &&
+    if(Iteration >= 3 &&
        (!InfiniteSearch && (StopOnPonderhit ||
                             t > AbsoluteMaxSearchTime ||
                             (RootMoveNumber == 1 &&