Drop to qsearch at low depth in razoring

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 3d755586d9885c9ee2310307e0feffee808e3d20..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)