Revert dynamic LMR

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c4446fc5d95bd4a6271fca322eb5b75ec8610d91..f18f2f2f65035a9c3740d92b551707e4030e8bfd 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -255,7 +255,7 @@ namespace {
                 Depth depth, int ply, int threadID);
   void sp_search(SplitPoint *sp, int threadID);
   void sp_search_pv(SplitPoint *sp, int threadID);
-  void init_node(const Position &pos, SearchStack ss[], int ply, 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);
@@ -956,7 +956,7 @@ namespace {
 
     // Initialize, and make an early exit in case of an aborted search,
     // an instant draw, maximum ply reached, etc.
-    init_node(pos, ss, ply, threadID);
+    init_node(ss, ply, threadID);
 
     // After init_node() that calls poll()
     if (AbortSearch || thread_should_stop(threadID))
@@ -1152,7 +1152,7 @@ namespace {
 
     // Initialize, and make an early exit in case of an aborted search,
     // an instant draw, maximum ply reached, etc.
-    init_node(pos, ss, ply, threadID);
+    init_node(ss, ply, threadID);
 
     // After init_node() that calls poll()
     if (AbortSearch || thread_should_stop(threadID))
@@ -1332,11 +1332,8 @@ namespace {
           && !move_is_castle(move)
           && !move_is_killer(move, ss[ply]))
       {
-          // 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);
+          ss[ply].reduction = OnePly;
+          value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true, threadID);
       }
       else
         value = beta; // Just to trigger next condition
@@ -1419,7 +1416,7 @@ namespace {
 
     // Initialize, and make an early exit in case of an aborted search,
     // an instant draw, maximum ply reached, etc.
-    init_node(pos, ss, ply, threadID);
+    init_node(ss, ply, threadID);
 
     // After init_node() that calls poll()
     if (AbortSearch || thread_should_stop(threadID))
@@ -1429,18 +1426,38 @@ namespace {
         return VALUE_DRAW;
 
     // Transposition table lookup, only when not in PV
+    TTEntry* tte = NULL;
     bool pvNode = (beta - alpha != 1);
     if (!pvNode)
     {
-        const TTEntry* tte = TT.retrieve(pos);
+        tte = TT.retrieve(pos);
         if (tte && ok_to_use_TT(tte, depth, beta, ply))
+        {
+            assert(tte->type() != VALUE_TYPE_EVAL);
+
             return value_from_tt(tte->value(), ply);
+        }
     }
 
     // Evaluate the position statically
     EvalInfo ei;
+    Value staticValue;
     bool isCheck = pos.is_check();
-    Value staticValue = (isCheck ? -VALUE_INFINITE : evaluate(pos, ei, threadID));
+    ei.futilityMargin = Value(0); // Manually initialize futilityMargin
+
+    if (isCheck)
+        staticValue = -VALUE_INFINITE;
+
+    else if (tte && tte->type() == VALUE_TYPE_EVAL)
+    {
+        // Use the cached evaluation score if possible
+        assert(tte->value() == evaluate(pos, ei, threadID));
+        assert(ei.futilityMargin == Value(0));
+
+        staticValue = tte->value();
+    }
+    else
+        staticValue = evaluate(pos, ei, threadID);
 
     if (ply == PLY_MAX - 1)
         return evaluate(pos, ei, threadID);
@@ -1451,8 +1468,10 @@ namespace {
 
     if (bestValue >= beta)
     {
-        // Update transposition table before to leave
-        TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_EXACT);
+        // 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);
+
         return bestValue;
     }
 
@@ -1462,7 +1481,7 @@ 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, isCheck ? NULL : &ei);
+    MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth);
     Move move;
     int moveCount = 0;
     Bitboard dcCandidates = mp.discovered_check_candidates();
@@ -1538,6 +1557,16 @@ namespace {
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
+    // Update transposition table
+    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);
+        else
+            TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_LOWER);
+    }
+
     // 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
@@ -1988,7 +2017,7 @@ namespace {
   // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
   // for user input and checks whether it is time to stop the search.
 
-  void init_node(const Position &pos, SearchStack ss[], int ply, int threadID) {
+  void init_node(SearchStack ss[], int ply, int threadID) {
     assert(ply >= 0 && ply < PLY_MAX);
     assert(threadID >= 0 && threadID < ActiveThreads);