Change multi-cut pruning condition

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d9543899a0f7844e2b817b3e2095f321a8ca51fc..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,
           // 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)
       }
 
       // 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
       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
           extension = ONE_PLY;
 
       // Passed pawn extension


@@ -1713,4 +1714,10 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
         if (dtz_available || rootMoves[0].tbScore <= VALUE_DRAW)
             Cardinality = 0;
     }
         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;
+    }

 }
 }