More aggressive dynamic LMR

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 549f19e211caecc575a10eb6fda327a6986e1d06..d08f698f531792aee62002abea194442f36aff30 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -193,7 +193,6 @@ namespace {
 
   // Iteration counters
   int Iteration;
-  bool LastIterations;
   BetaCounterType BetaCounter;
 
   // Scores and number of times the best move changed for each iteration:
@@ -207,7 +206,7 @@ namespace {
   int SearchStartTime;
   int MaxNodes, MaxDepth;
   int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
-  Move BestRootMove, PonderMove, EasyMove;
+  Move EasyMove;
   int RootMoveNumber;
   bool InfiniteSearch;
   bool PonderSearch;
@@ -369,8 +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++)
   {
@@ -661,7 +658,6 @@ namespace {
     ValueByIteration[0] = Value(0);
     ValueByIteration[1] = rml.get_move_score(0);
     Iteration = 1;
-    LastIterations = false;
 
     EasyMove = rml.scan_for_easy_move();
 
@@ -716,9 +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.
@@ -755,6 +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];
@@ -1334,8 +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
@@ -1396,6 +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;
   }
 
@@ -1424,10 +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;
@@ -1450,7 +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;