Change multi-cut pruning condition

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 0e10f44f3a77f70538539365f311259b2b2e9e65..f682da3ae6e8e9d6c92d709225871c168a3f9464 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -913,10 +913,11 @@ moves_loop: // When in check, search starts from here
           // Multi-cut pruning
           // Our ttMove is assumed to fail high, and now we failed high also on a reduced
           // search without the ttMove. So we assume this expected Cut-node is not singular,
-          // that is multiple moves fail high, and we can prune the whole subtree by returning
-          // the hard beta bound.
-          else if (cutNode && singularBeta > beta)
-              return beta;
+          // that multiple moves fail high, and we can prune the whole subtree by returning
+          // a soft bound.
+          else if (   eval >= beta
+                   && singularBeta >= beta)
+              return singularBeta;
       }
 
       // Check extension (~2 Elo)
@@ -932,7 +933,7 @@ moves_loop: // When in check, search starts from here
       else if (   PvNode
                && pos.rule50_count() > 18
                && depth < 3 * ONE_PLY
-               && ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid too deep searches
+               && ++thisThread->shuffleExts < thisThread->nodes.load(std::memory_order_relaxed) / 4)  // To avoid too many extensions
           extension = ONE_PLY;
 
       // Passed pawn extension
@@ -980,7 +981,7 @@ moves_loop: // When in check, search starts from here
               if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
                   continue;
           }
-          else if ((!givesCheck || !(pos.blockers_for_king(~us) & from_sq(move)))
+          else if ((!givesCheck || !extension)
                   && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
                   continue;
       }
@@ -1363,6 +1364,7 @@ moves_loop: // When in check, search starts from here
 
       // Don't search moves with negative SEE values
       if (  (!inCheck || evasionPrunable)
+          && (!givesCheck || !(pos.blockers_for_king(~pos.side_to_move()) & from_sq(move)))
           && !pos.see_ge(move))
           continue;
 
@@ -1712,4 +1714,10 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
         if (dtz_available || rootMoves[0].tbScore <= VALUE_DRAW)
             Cardinality = 0;
     }
+    else
+    {
+        // Clean up if root_probe() and root_probe_wdl() have failed
+        for (auto& m : rootMoves)
+            m.tbRank = 0;
+    }
 }