Be clear about not LMR the ttMove

Currently a ttMove is reduced with ss->reduction = DEPTH_ZERO,
so it is actually not reduced (as it should be), but the
trick works just becuase it happens that ttMove is the first
to be tried and

reduction(depth, 1)

Always returns zero. So explicitly forbid reduction of ttMove
in the LMR condition. This is much clear and self-documented.

No functional change.

diff --git a/src/search.cpp b/src/search.cpp
index 86f6fff0c694f86679c429d30f16f562a5def0f4..27669d9d9bb899f6badeba3293f1cf765eb7a092 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -400,6 +400,7 @@ namespace {
 
             // Sort the PV lines searched so far and update the GUI
             sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
+
             if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000)
                 sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
         }
@@ -922,8 +923,9 @@ split_point_start: // At split points actual search starts from here
           && !pvMove
           && !captureOrPromotion
           && !dangerous
-          &&  ss->killers[0] != move
-          &&  ss->killers[1] != move)
+          &&  move != ttMove
+          &&  move != ss->killers[0]
+          &&  move != ss->killers[1])
       {
           ss->reduction = reduction<PvNode>(depth, moveCount);
           Depth d = std::max(newDepth - ss->reduction, ONE_PLY);