Drop to qsearch at low depth in razoring

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index dfe690b4d6498ec65c016c200696acb39175ca15..aa63fcb4392d2fbe839b91b2c3bdfc1e764dd69d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -582,6 +582,10 @@ namespace {
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         && !pos.pawn_on_7th(pos.side_to_move()))
     {
+        if (   depth <= ONE_PLY
+            && eval + razor_margin(3 * ONE_PLY) <= alpha)
+            return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
+
         Value ralpha = alpha - razor_margin(depth);
         Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
         if (v <= ralpha)
@@ -1017,18 +1021,18 @@ moves_loop: // When in check and at SpNode search starts from here
     // must be mate or stalemate. If we are in a singular extension search then
     // return a fail low score.
     if (!moveCount)
-        return  excludedMove ? alpha
-              : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+        bestValue = excludedMove ? alpha
+                   :     inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+
+    // Quiet best move: update killers, history, countermoves and followupmoves
+    else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
+        update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
 
     TT.store(posKey, value_to_tt(bestValue, ss->ply),
              bestValue >= beta  ? BOUND_LOWER :
              PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
              depth, bestMove, ss->staticEval);
 
-    // Quiet best move: update killers, history, countermoves and followupmoves
-    if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
-        update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
-
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
     return bestValue;