Do not update killers in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 627a64af2cc5b4ab6da5b31b59a809dcceabd428..df4c854030d9ba82b74dece6f469b4ba7057793b 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -188,12 +188,6 @@ namespace {
   // Dynamic razoring margin based on depth
   inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
 
-  // Step 8. Null move search with verification search
-
-  // Null move margin. A null move search will not be done if the static
-  // evaluation of the position is more than NullMoveMargin below beta.
-  const Value NullMoveMargin = Value(0x200);
-
   // Maximum depth for use of dynamic threat detection when null move fails low
   const Depth ThreatDepth = 5 * ONE_PLY;
 
@@ -1094,14 +1088,11 @@ namespace {
         return refinedValue - futility_margin(depth, 0);
 
     // Step 8. Null move search with verification search (is omitted in PV nodes)
-    // When we jump directly to qsearch() we do a null move only if static value is
-    // at least beta. Otherwise we do a null move if static value is not more than
-    // NullMoveMargin under beta.
     if (   !PvNode
         && !ss->skipNullMove
         &&  depth > ONE_PLY
         && !isCheck
-        &&  refinedValue >= beta - (depth >= 4 * ONE_PLY ? NullMoveMargin : 0)
+        &&  refinedValue >= beta
         && !value_is_mate(beta)
         &&  pos.non_pawn_material(pos.side_to_move()))
     {
@@ -1511,7 +1502,6 @@ namespace {
       evasionPrunable =   isCheck
                        && bestValue > value_mated_in(PLY_MAX)
                        && !pos.move_is_capture(move)
-                       && pos.type_of_piece_on(move_from(move)) != KING
                        && !pos.can_castle(pos.side_to_move());
 
       // Don't search moves with negative SEE values
@@ -1554,11 +1544,6 @@ namespace {
     ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
     TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, d, ss->bestMove, ss->eval, evalMargin);
 
-    // Update killers only for checking moves that fails high
-    if (    bestValue >= beta
-        && !pos.move_is_capture_or_promotion(ss->bestMove))
-        update_killers(ss->bestMove, ss);
-
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
     return bestValue;