Extension for king moves changing castling rights

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c78a71a96e3c258d6e749b973d878d0a890e0546..8a32e827488739ea351a4ee77d0532138b578ffa 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -387,7 +387,7 @@ void Thread::search() {
           if (rootDepth >= 5 * ONE_PLY)
           {
               Value previousScore = rootMoves[pvIdx].previousScore;
-              delta = Value(18);
+              delta = Value(20);
               alpha = std::max(previousScore - delta,-VALUE_INFINITE);
               beta  = std::min(previousScore + delta, VALUE_INFINITE);
 
@@ -401,9 +401,11 @@ void Thread::search() {
           // Start with a small aspiration window and, in the case of a fail
           // high/low, re-search with a bigger window until we don't fail
           // high/low anymore.
+          int failedHighCnt = 0;
           while (true)
           {
-              bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false);
+              Depth adjustedDepth = std::max(ONE_PLY, rootDepth - failedHighCnt * ONE_PLY);
+              bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
 
               // Bring the best move to the front. It is critical that sorting
               // is done with a stable algorithm because all the values but the
@@ -436,12 +438,17 @@ void Thread::search() {
 
                   if (mainThread)
                   {
+                      failedHighCnt = 0;
                       failedLow = true;
                       Threads.stopOnPonderhit = false;
                   }
               }
               else if (bestValue >= beta)
+              {
                   beta = std::min(bestValue + delta, VALUE_INFINITE);
+                  if (mainThread)
+                         ++failedHighCnt;
+              }
               else
                   break;
 
@@ -936,6 +943,12 @@ moves_loop: // When in check, search starts from here
                &&  pos.see_ge(move))
           extension = ONE_PLY;
 
+      // Extension for king moves that change castling rights
+      if (   type_of(movedPiece) == KING
+          && pos.can_castle(us)
+          && depth < 12 * ONE_PLY)
+          extension = ONE_PLY;
+
       // Calculate new depth for this move
       newDepth = depth - ONE_PLY + extension;
 
@@ -1132,8 +1145,6 @@ moves_loop: // When in check, search starts from here
                   break;
               }
           }
-          else if (PvNode && !rootNode && value == alpha)
-              update_pv(ss->pv, move, (ss+1)->pv);
       }
 
       if (move != bestMove)