Increase reduction based on the number of best move changes.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 12c32194eb95436726f0c484f7cdd2988a65b20e..56b56733fb2771aa998030887370622a408ff786 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -521,10 +521,14 @@ void Thread::search() {
           }
           double bestMoveInstability = 1 + 2 * totBestMoveChanges / Threads.size();
 
-          double totalTime = rootMoves.size() == 1 ? 0 :
-                             Time.optimum() * fallingEval * reduction * bestMoveInstability;
+          double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability;
 
-          // Stop the search if we have exceeded the totalTime, at least 1ms search
+          // Cap used time in case of a single legal move for a better viewer experience in tournaments
+          // yielding correct scores and sufficiently fast moves.
+          if (rootMoves.size() == 1)
+              totalTime = std::min(500.0, totalTime);
+
+          // Stop the search if we have exceeded the totalTime
           if (Time.elapsed() > totalTime)
           {
               // If we are allowed to ponder do not stop the search now but
@@ -1165,6 +1169,9 @@ moves_loop: // When in check, search starts from here
           if (ss->ttPv)
               r -= 2;
 
+          if (!PvNode && depth > 10 && thisThread->bestMoveChanges <= 2)
+              r++;
+
           if (moveCountPruning && !formerPv)
               r++;
 
@@ -1521,7 +1528,7 @@ moves_loop: // When in check, search starts from here
       moveCount++;
 
       // Futility pruning
-      if (   !ss->inCheck
+      if (    bestValue > VALUE_TB_LOSS_IN_MAX_PLY
           && !givesCheck
           &&  futilityBase > -VALUE_KNOWN_WIN
           && !pos.advanced_pawn_push(move))
@@ -1548,7 +1555,7 @@ moves_loop: // When in check, search starts from here
       }
 
       // Do not search moves with negative SEE values
-      if (   !ss->inCheck
+      if (    bestValue > VALUE_TB_LOSS_IN_MAX_PLY
           && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))
           && !pos.see_ge(move))
           continue;