Don't futility-prune ttMove

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index e5063b2453b01ff490f167993ddd3099f2a60a2b..c4e061bd6cd1afb5d8bcc0035bda587668adb86d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -334,7 +334,6 @@ int perft(Position& pos, Depth depth)
 {
     Move move;
     MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H);
-    Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
     int sum = 0;
 
     // If we are at the last ply we don't need to do and undo
@@ -346,10 +345,11 @@ int perft(Position& pos, Depth depth)
     }
 
     // Loop through all legal moves
+    CheckInfo ci(pos);
     while ((move = mp.get_next_move()) != MOVE_NONE)
     {
       StateInfo st;
-      pos.do_move(move, st, dcCandidates);
+      pos.do_move(move, st, ci.dcCandidates, pos.move_is_check(move, ci));
       sum += perft(pos, depth - OnePly);
       pos.undo_move(move);
     }
@@ -862,7 +862,7 @@ namespace {
 
     Value oldAlpha = alpha;
     Value value;
-    Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
+    CheckInfo ci(pos);
 
     // Loop through all the moves in the root move list
     for (int i = 0; i <  rml.move_count() && !AbortSearch; i++)
@@ -904,7 +904,7 @@ namespace {
         newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
 
         // Make the move, and search it
-        pos.do_move(move, st, dcCandidates);
+        pos.do_move(move, st, ci.dcCandidates);
 
         if (i < MultiPV)
         {
@@ -1065,7 +1065,6 @@ namespace {
     Move movesSearched[256];
     EvalInfo ei;
     StateInfo st;
-    Bitboard dcCandidates;
     const TTEntry* tte;
     Move ttMove, move;
     Depth ext, newDepth;
@@ -1115,7 +1114,6 @@ namespace {
     isCheck = pos.is_check();
     mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
     CheckInfo ci(pos);
-    dcCandidates = ci.dcCandidates;
     MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
 
     // Loop through all legal moves until no moves remain or a beta cutoff
@@ -1137,7 +1135,7 @@ namespace {
       newDepth = depth - OnePly + ext;
 
       // Make and search the move
-      pos.do_move(move, st, dcCandidates);
+      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
 
       if (moveCount == 1) // The first move in list is the PV
           value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
@@ -1211,7 +1209,7 @@ namespace {
           && !AbortSearch
           && !thread_should_stop(threadID)
           && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, VALUE_NONE, depth,
-                   &moveCount, &mp, dcCandidates, threadID, true))
+                   &moveCount, &mp, ci.dcCandidates, threadID, true))
           break;
     }
 
@@ -1258,7 +1256,6 @@ namespace {
     Move movesSearched[256];
     EvalInfo ei;
     StateInfo st;
-    Bitboard dcCandidates;
     const TTEntry* tte;
     Move ttMove, move;
     Depth ext, newDepth;
@@ -1373,7 +1370,6 @@ namespace {
     // to search all moves.
     MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
     CheckInfo ci(pos);
-    dcCandidates = ci.dcCandidates;
     futilityValue = VALUE_NONE;
     useFutilityPruning = depth < SelectiveDepth && !isCheck;
 
@@ -1402,7 +1398,8 @@ namespace {
       // Futility pruning
       if (    useFutilityPruning
           && !dangerous
-          && !captureOrPromotion)
+          && !captureOrPromotion
+          &&  move != ttMove)
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)
@@ -1427,7 +1424,7 @@ namespace {
       }
 
       // Make and search the move
-      pos.do_move(move, st, dcCandidates);
+      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
@@ -1473,7 +1470,7 @@ namespace {
           && !AbortSearch
           && !thread_should_stop(threadID)
           && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, approximateEval, depth, &moveCount,
-                   &mp, dcCandidates, threadID, false))
+                   &mp, ci.dcCandidates, threadID, false))
         break;
     }
 
@@ -1522,10 +1519,9 @@ namespace {
 
     EvalInfo ei;
     StateInfo st;
-    Bitboard dcCandidates;
     Move ttMove, move;
     Value staticValue, bestValue, value, futilityValue;
-    bool isCheck, enoughMaterial;
+    bool isCheck, enoughMaterial, moveIsCheck;
     const TTEntry* tte = NULL;
     int moveCount = 0;
     bool pvNode = (beta - alpha != 1);
@@ -1595,7 +1591,6 @@ namespace {
     // queen promotions and checks (only if depth == 0) will be generated.
     MovePicker mp = MovePicker(pos, ttMove, depth, H);
     CheckInfo ci(pos);
-    dcCandidates = ci.dcCandidates;
     enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
 
     // Loop through the moves until no moves remain or a beta cutoff
@@ -1608,12 +1603,15 @@ namespace {
       moveCount++;
       ss[ply].currentMove = move;
 
+      moveIsCheck = pos.move_is_check(move, ci);
+
       // Futility pruning
       if (   enoughMaterial
           && !isCheck
           && !pvNode
+          && !moveIsCheck
+          &&  move != ttMove
           && !move_is_promotion(move)
-          && !pos.move_is_check(move, ci)
           && !pos.move_is_passed_pawn_push(move))
       {
           futilityValue =  staticValue
@@ -1639,7 +1637,7 @@ namespace {
           continue;
 
       // Make and search the move
-      pos.do_move(move, st, dcCandidates);
+      pos.do_move(move, st, ci.dcCandidates, moveIsCheck);
       value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
       pos.undo_move(move);
 
@@ -1766,7 +1764,7 @@ namespace {
 
       // Make and search the move.
       StateInfo st;
-      pos.do_move(move, st, sp->dcCandidates);
+      pos.do_move(move, st, sp->dcCandidates, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
@@ -1872,7 +1870,7 @@ namespace {
 
       // Make and search the move.
       StateInfo st;
-      pos.do_move(move, st, sp->dcCandidates);
+      pos.do_move(move, st, sp->dcCandidates, moveIsCheck);
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.