Cleanup of likelyFailLow logic

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 99c2b09f9ef42b4032c95864e7f4e0e497147ec5..bcd53f9eefe33194788faac0e8f3b5284e6d3b94 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1006,6 +1006,13 @@ moves_loop: // When in check, search starts from here
     value = bestValue;
     singularQuietLMR = moveCountPruning = false;
 
+    // Indicate PvNodes that will probably fail low if the node was searched
+    // at a depth equal or greater than the current depth, and the result of this search was a fail low.
+    bool likelyFailLow =    PvNode
+                         && ttMove
+                         && (tte->bound() & BOUND_UPPER)
+                         && tte->depth() >= depth;
+
     // Mark this node as being searched
     ThreadHolding th(thisThread, posKey, ss->ply);
 
@@ -1044,14 +1051,6 @@ moves_loop: // When in check, search starts from here
       movedPiece = pos.moved_piece(move);
       givesCheck = pos.gives_check(move);
 
-      // Indicate PvNodes that will probably fail low if node was searched with non-PV search
-      // at depth equal or greater to current depth and result of this search was far below alpha
-      bool likelyFailLow =    PvNode
-                           && ttMove
-                           && (tte->bound() & BOUND_UPPER)
-                           && ttValue < alpha + 200 + 100 * depth
-                           && tte->depth() >= depth;
-
       // Calculate new depth for this move
       newDepth = depth - 1;
 
@@ -1130,6 +1129,8 @@ moves_loop: // When in check, search starts from here
           {
               extension = 1;
               singularQuietLMR = !ttCapture;
+              if (!PvNode && value < singularBeta - 140)
+                  extension = 2;
           }
 
           // Multi-cut pruning
@@ -1153,11 +1154,6 @@ moves_loop: // When in check, search starts from here
           }
       }
 
-      // Check extension (~2 Elo)
-      else if (    givesCheck
-               && (pos.is_discovered_check_on_king(~us, move) || pos.see_ge(move)))
-          extension = 1;
-
       // Add extension to new depth
       newDepth += extension;