Don't futility-prune ttMove

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 23066d8f5d7186aa5391dca08822787624c53e0d..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;
@@ -1103,11 +1102,8 @@ namespace {
     tte = TT.retrieve(pos.get_key());
     ttMove = (tte ? tte->move() : MOVE_NONE);
 
-    // Go with internal iterative deepening if we don't have a TT move or
-    // if search depth is more then 4*OnePly higher then TT move depth.
-    if (   UseIIDAtPVNodes
-        && depth >= 5*OnePly
-        &&(!ttMove || depth > tte->depth() + 4*OnePly))
+    // Go with internal iterative deepening if we don't have a TT move
+    if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly)
     {
         search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
         ttMove = ss[ply].pv[ply];
@@ -1117,7 +1113,7 @@ namespace {
     // to search all moves
     isCheck = pos.is_check();
     mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
-    dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
+    CheckInfo ci(pos);
     MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
 
     // Loop through all legal moves until no moves remain or a beta cutoff
@@ -1129,7 +1125,7 @@ namespace {
       assert(move_is_ok(move));
 
       singleReply = (isCheck && mp.number_of_evasions() == 1);
-      moveIsCheck = pos.move_is_check(move, dcCandidates);
+      moveIsCheck = pos.move_is_check(move, ci);
       captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
       movesSearched[moveCount++] = ss[ply].currentMove = move;
@@ -1139,7 +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);
@@ -1213,7 +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;
     }
 
@@ -1260,7 +1256,6 @@ namespace {
     Move movesSearched[256];
     EvalInfo ei;
     StateInfo st;
-    Bitboard dcCandidates;
     const TTEntry* tte;
     Move ttMove, move;
     Depth ext, newDepth;
@@ -1374,7 +1369,7 @@ namespace {
     // Initialize a MovePicker object for the current position, and prepare
     // to search all moves.
     MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
-    dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
+    CheckInfo ci(pos);
     futilityValue = VALUE_NONE;
     useFutilityPruning = depth < SelectiveDepth && !isCheck;
 
@@ -1391,7 +1386,7 @@ namespace {
       assert(move_is_ok(move));
 
       singleReply = (isCheck && mp.number_of_evasions() == 1);
-      moveIsCheck = pos.move_is_check(move, dcCandidates);
+      moveIsCheck = pos.move_is_check(move, ci);
       captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
       movesSearched[moveCount++] = ss[ply].currentMove = move;
@@ -1403,7 +1398,8 @@ namespace {
       // Futility pruning
       if (    useFutilityPruning
           && !dangerous
-          && !captureOrPromotion)
+          && !captureOrPromotion
+          &&  move != ttMove)
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)
@@ -1428,7 +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.
@@ -1474,7 +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;
     }
 
@@ -1523,10 +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 +1590,7 @@ namespace {
     // to search the moves.  Because the depth is <= 0 here, only captures,
     // queen promotions and checks (only if depth == 0) will be generated.
     MovePicker mp = MovePicker(pos, ttMove, depth, H);
-    dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
+    CheckInfo ci(pos);
     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, dcCandidates)
           && !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);
 
@@ -1701,6 +1699,7 @@ namespace {
     assert(ActiveThreads > 1);
 
     Position pos = Position(sp->pos);
+    CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
     Value value;
     Move move;
@@ -1714,7 +1713,7 @@ namespace {
     {
       assert(move_is_ok(move));
 
-      bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
+      bool moveIsCheck = pos.move_is_check(move, ci);
       bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
       lock_grab(&(sp->lock));
@@ -1765,7 +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.
@@ -1844,6 +1843,7 @@ namespace {
     assert(ActiveThreads > 1);
 
     Position pos = Position(sp->pos);
+    CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
     Value value;
     Move move;
@@ -1852,7 +1852,7 @@ namespace {
            && !thread_should_stop(threadID)
            && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
     {
-      bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
+      bool moveIsCheck = pos.move_is_check(move, ci);
       bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
       assert(move_is_ok(move));
@@ -1870,7 +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.