Remove reduction for moving threatened piece

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index b2983f6647ae860093d9d92d9587cd7faa23437e..2fcbc7df2a524d1e33617814f45bbc75696c957b 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -607,14 +607,7 @@ namespace {
     (ss+2)->cutoffCnt    = 0;
     ss->doubleExtensions = (ss-1)->doubleExtensions;
     Square prevSq        = is_ok((ss-1)->currentMove) ? to_sq((ss-1)->currentMove) : SQ_NONE;
-
-    // Initialize statScore to zero for the grandchildren of the current position.
-    // So statScore is shared between all grandchildren and only the first grandchild
-    // starts with statScore = 0. Later grandchildren start with the last calculated
-    // statScore of the previous grandchild. This influences the reduction rules in
-    // LMR which are based on the statScore of parent position.
-    if (!rootNode)
-        (ss+2)->statScore = 0;
+    ss->statScore        = 0;
 
     // Step 4. Transposition table lookup.
     excludedMove = ss->excludedMove;
@@ -1012,7 +1005,6 @@ moves_loop: // When in check, search starts here
           {
               // Futility pruning for captures (~2 Elo)
               if (   !givesCheck
-                  && !PvNode
                   && lmrDepth < 6
                   && !ss->inCheck
                   && ss->staticEval + 182 + 230 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
@@ -1065,9 +1057,8 @@ moves_loop: // When in check, search starts here
 
               lmrDepth = std::max(lmrDepth, 0);
 
-              Bitboard occupied;
               // Prune moves with negative SEE (~4 Elo)
-              if (!pos.see_ge(move, occupied, Value(-24 * lmrDepth * lmrDepth - 15 * lmrDepth)))
+              if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 15 * lmrDepth)))
                   continue;
           }
       }
@@ -1190,11 +1181,6 @@ moves_loop: // When in check, search starts here
       if (singularQuietLMR)
           r--;
 
-      // Decrease reduction if we move a threatened piece (~1 Elo)
-      if (   depth > 9
-          && (mp.threatenedPieces & from_sq(move)))
-          r--;
-
       // Increase reduction if next ply has a lot of fail high (~5 Elo)
       if ((ss+1)->cutoffCnt > 3)
           r++;
@@ -1552,7 +1538,6 @@ moves_loop: // When in check, search starts here
                                       prevSq);
 
     int quietCheckEvasions = 0;
-    Bitboard occupied;
 
     // Step 5. Loop through all pseudo-legal moves until no moves remain
     // or a beta cutoff occurs.
@@ -1589,7 +1574,7 @@ moves_loop: // When in check, search starts here
               continue;
           }
 
-          if (futilityBase <= alpha && !pos.see_ge(move, occupied, VALUE_ZERO + 1))
+          if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1))
           {
               bestValue = std::max(bestValue, futilityBase);
               continue;
@@ -1608,7 +1593,7 @@ moves_loop: // When in check, search starts here
           continue;
 
       // Do not search moves with bad enough SEE values (~5 Elo)
-      if (!pos.see_ge(move, occupied, Value(-110)))
+      if (!pos.see_ge(move, Value(-110)))
           continue;
     }