X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=3cd54b00fd0e8889556dbc0f867feb3d170d572d;hp=c1a91a97ea0f637ca1658bb946c1886060f3ce65;hb=dd884b65b7d926c7a8b01c372ca026bef3fc84a8;hpb=423b8b9ded6d3128680a87fcede0016d93fec9ba

diff --git a/src/search.cpp b/src/search.cpp
index c1a91a97..3cd54b00 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -284,7 +284,7 @@ namespace {
   bool connected_moves(const Position& pos, Move m1, Move m2);
   bool value_is_mate(Value value);
   bool move_is_killer(Move m, const SearchStack& ss);
-  Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
+  Depth extension(const Position& pos, Move m, Depth depth, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
   bool ok_to_do_nullmove(const Position& pos);
   bool ok_to_prune(const Position& pos, Move m, Move threat, Depth d);
   bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
@@ -900,7 +900,7 @@ namespace {
         // Decide search depth for this move
         bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
         bool dangerous;
-        ext = extension(pos, move, true, captureOrPromotion, pos.move_is_check(move), false, false, &dangerous);
+        ext = extension(pos, move, Depth(100), true, captureOrPromotion, pos.move_is_check(move), false, false, &dangerous);
         newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
 
         // Make the move, and search it
@@ -1103,8 +1103,11 @@ 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
-    if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly)
+    // 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))
     {
         search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
         ttMove = ss[ply].pv[ply];
@@ -1132,7 +1135,7 @@ namespace {
       movesSearched[moveCount++] = ss[ply].currentMove = move;
 
       // Decide the new search depth
-      ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous);
+      ext = extension(pos, move, depth, true, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous);
       newDepth = depth - OnePly + ext;
 
       // Make and search the move
@@ -1394,7 +1397,7 @@ namespace {
       movesSearched[moveCount++] = ss[ply].currentMove = move;
 
       // Decide the new search depth
-      ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous);
+      ext = extension(pos, move, depth, false, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous);
       newDepth = depth - OnePly + ext;
 
       // Futility pruning
@@ -1722,7 +1725,7 @@ namespace {
 
       // Decide the new search depth.
       bool dangerous;
-      Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
+      Depth ext = extension(pos, move, sp->depth, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
       Depth newDepth = sp->depth - OnePly + ext;
 
       // Prune?
@@ -1862,7 +1865,7 @@ namespace {
 
       // Decide the new search depth.
       bool dangerous;
-      Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
+      Depth ext = extension(pos, move, sp->depth, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
       Depth newDepth = sp->depth - OnePly + ext;
 
       // Make and search the move.
@@ -2298,7 +2301,7 @@ namespace {
   // extended, as example because the corresponding UCI option is set to zero,
   // the move is marked as 'dangerous' so, at least, we avoid to prune it.
 
-  Depth extension(const Position& pos, Move m, bool pvNode, bool captureOrPromotion,
+  Depth extension(const Position& pos, Move m, Depth depth, bool pvNode, bool captureOrPromotion,
                   bool check, bool singleReply, bool mateThreat, bool* dangerous) {
 
     assert(m != MOVE_NONE);
@@ -2318,6 +2321,19 @@ namespace {
             result += MateThreatExtension[pvNode];
     }
 
+    if (   pvNode
+        && captureOrPromotion
+        && pos.type_of_piece_on(move_to(m)) != PAWN
+        && pos.see_sign(m) >= 0)
+    {
+        result += OnePly/2;
+        *dangerous = true;
+    }
+
+    // Do not extend at low depths
+    if (!pvNode && depth < 4*OnePly)
+        return Min(result, OnePly); // Further test with Min(result, OnePly / 2)
+
     if (pos.type_of_piece_on(move_from(m)) == PAWN)
     {
         Color c = pos.side_to_move();
@@ -2344,15 +2360,6 @@ namespace {
         *dangerous = true;
     }
 
-    if (   pvNode
-        && captureOrPromotion
-        && pos.type_of_piece_on(move_to(m)) != PAWN
-        && pos.see_sign(m) >= 0)
-    {
-        result += OnePly/2;
-        *dangerous = true;
-    }
-
     return Min(result, OnePly);
   }