Simplified select best thread (#958)

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 8089130e594c153a8f87955fde79f4a05dbff1ab..a9fc1c6d4c80b41aec8c20c4b6b2e7c070760050 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -153,11 +153,11 @@ namespace {
     {1, 0, 0, 0, 0, 1, 1 ,1},
   };
 
+  const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
+
   Value bonus(Depth depth)   { int d = depth / ONE_PLY ; return  Value(d * d + 2 * d - 2); }
   Value penalty(Depth depth) { int d = depth / ONE_PLY ; return -Value(d * d + 4 * d + 1); }
 
-  const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
-
   EasyMoveManager EasyMove;
   Value DrawValue[COLOR_NB];
 
@@ -312,9 +312,13 @@ void MainThread::search() {
       &&  rootMoves[0].pv[0] != MOVE_NONE)
   {
       for (Thread* th : Threads)
-          if (   th->completedDepth > bestThread->completedDepth
-              && th->rootMoves[0].score > bestThread->rootMoves[0].score)
+      {
+          Depth depthDiff = th->completedDepth - bestThread->completedDepth;
+          Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score;
+
+          if (scoreDiff > 0 && depthDiff >= 0)
               bestThread = th;
+      }
   }
 
   previousScore = bestThread->rootMoves[0].score;
@@ -597,7 +601,7 @@ namespace {
     if (!rootNode)
     {
         // Step 2. Check for aborted search and immediate draw
-        if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY)
+        if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
             return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos)
                                                   : DrawValue[pos.side_to_move()];
 
@@ -1074,13 +1078,6 @@ moves_loop: // When in check search starts from here
 
           if (value > alpha)
           {
-              // If there is an easy move for this position, clear it if unstable
-              if (    PvNode
-                  &&  thisThread == Threads.main()
-                  &&  EasyMove.get(pos.key())
-                  && (move != EasyMove.get(pos.key()) || moveCount > 1))
-                  EasyMove.clear();
-
               bestMove = move;
 
               if (PvNode && !rootNode) // Update pv even in fail-high case
@@ -1180,7 +1177,7 @@ moves_loop: // When in check search starts from here
     ss->ply = (ss-1)->ply + 1;
 
     // Check for an instant draw or if the maximum ply has been reached
-    if (pos.is_draw() || ss->ply >= MAX_PLY)
+    if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
         return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos)
                                               : DrawValue[pos.side_to_move()];