Remove unneeded & incorrect check.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index e75db243cfcb2cb01d760c885536b29bc5a5992c..26010108dd4c94dfe6066261802b639c8a6cff2d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -61,6 +61,9 @@ namespace {
   // Different node types, used as a template parameter
   enum NodeType { NonPV, PV };
 
+  constexpr uint64_t ttHitAverageWindow     = 4096;
+  constexpr uint64_t ttHitAverageResolution = 1024;
+
   // Razor and futility margins
   constexpr int RazorMargin = 661;
   Value futility_margin(Depth d, bool improving) {
@@ -363,6 +366,7 @@ void Thread::search() {
       multiPV = std::max(multiPV, (size_t)4);
 
   multiPV = std::min(multiPV, rootMoves.size());
+  ttHitAverage = ttHitAverageWindow * ttHitAverageResolution / 2;
 
   int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns
 
@@ -665,6 +669,9 @@ namespace {
     ttMove =  rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
             : ttHit    ? tte->move() : MOVE_NONE;
     ttPv = PvNode || (ttHit && tte->is_pv());
+    // thisThread->ttHitAverage can be used to approximate the running average of ttHit
+    thisThread->ttHitAverage =   (ttHitAverageWindow - 1) * thisThread->ttHitAverage / ttHitAverageWindow
+                                + ttHitAverageResolution * ttHit;
 
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
@@ -967,8 +974,7 @@ moves_loop: // When in check, search starts from here
           moveCountPruning = moveCount >= futility_move_count(improving, depth);
 
           if (   !captureOrPromotion
-              && !givesCheck
-              && (!PvNode || !pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg))
+              && !givesCheck)
           {
               // Reduced depth of the next LMR search
               int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
@@ -1027,8 +1033,7 @@ moves_loop: // When in check, search starts from here
           // search without the ttMove. So we assume this expected Cut-node is not singular,
           // that multiple moves fail high, and we can prune the whole subtree by returning
           // a soft bound.
-          else if (   eval >= beta
-                   && singularBeta >= beta)
+          else if (singularBeta >= beta)
               return singularBeta;
       }
 
@@ -1043,6 +1048,12 @@ moves_loop: // When in check, search starts from here
                && pos.pawn_passed(us, to_sq(move)))
           extension = 1;
 
+      // Last captures extension
+      else if (   PvNode
+               && PieceValue[EG][pos.captured_piece()] > PawnValueEg
+               && pos.non_pawn_material() <= 2 * RookValueMg)
+          extension = 1;
+
       // Castling extension
       if (type_of(move) == CASTLING)
           extension = 1;
@@ -1078,10 +1089,15 @@ moves_loop: // When in check, search starts from here
           && (  !captureOrPromotion
               || moveCountPruning
               || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
-              || cutNode))
+              || cutNode
+              || thisThread->ttHitAverage < 384 * ttHitAverageResolution * ttHitAverageWindow / 1024))
       {
           Depth r = reduction(improving, depth, moveCount);
 
+          // Decrease reduction if the ttHit running average is large
+          if (thisThread->ttHitAverage > 544 * ttHitAverageResolution * ttHitAverageWindow / 1024)
+              r--;
+
           // Reduction if other threads are searching this position.
           if (th.marked())
               r++;