Simplify extensions

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 4384b58dd5c89a21ab10d40ccb0de6c88525fc82..789492fd95225965194b8262affc992978ea53de 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -236,17 +236,19 @@ void Search::think() {
   }
 
   // Reset the threads, still sleeping: will be wake up at split time
-  for (size_t i = 0; i < Threads.size(); i++)
+  for (size_t i = 0; i < Threads.size(); ++i)
       Threads[i]->maxPly = 0;
 
   Threads.sleepWhileIdle = Options["Idle Threads Sleep"];
 
   // Set best timer interval to avoid lagging under time pressure. Timer is
-  // used to check for remaining available thinking time. Timer will be started
-  // at the end of first iteration to avoid returning with a random move.
+  // used to check for remaining available thinking time.
   Threads.timer->msec =
   Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) :
-                  Limits.nodes ? 2 * TimerResolution : 100;
+                  Limits.nodes ? 2 * TimerResolution
+                               : 100;
+
+  Threads.timer->notify_one(); // Wake up the recurring timer
 
   id_loop(RootPos); // Let's start searching !
 
@@ -335,7 +337,7 @@ namespace {
 
         // Save last iteration's scores before first PV line is searched and all
         // the move scores but the (new) PV are set to -VALUE_INFINITE.
-        for (size_t i = 0; i < RootMoves.size(); i++)
+        for (size_t i = 0; i < RootMoves.size(); ++i)
             RootMoves[i].prevScore = RootMoves[i].score;
 
         // MultiPV loop. We perform a full root search for each PV line
@@ -365,7 +367,7 @@ namespace {
 
                 // Write PV back to transposition table in case the relevant
                 // entries have been overwritten during the search.
-                for (size_t i = 0; i <= PVIdx; i++)
+                for (size_t i = 0; i <= PVIdx; ++i)
                     RootMoves[i].insert_pv_in_tt(pos);
 
                 // If search has been stopped return immediately. Sorting and
@@ -400,10 +402,6 @@ namespace {
                 assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
             }
 
-            // Wake up the recurring timer after first iteration is finished
-            if (depth == 1)
-                Threads.timer->notify_one();
-
             // Sort the PV lines searched so far and update the GUI
             std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
 
@@ -611,8 +609,7 @@ namespace {
 
         // Can ttValue be used as a better position evaluation?
         if (ttValue != VALUE_NONE)
-            if (   ((tte->bound() & BOUND_LOWER) && ttValue > eval)
-                || ((tte->bound() & BOUND_UPPER) && ttValue < eval))
+            if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER))
                 eval = ttValue;
     }
     else
@@ -832,13 +829,10 @@ moves_loop: // When in check and at SpNode search starts from here
                  || pos.is_passed_pawn_push(move)
                  || type_of(move) == CASTLE;
 
-      // Step 12. Extend checks and, in PV nodes, also dangerous moves
-      if (PvNode && dangerous)
+      // Step 12. Extend checks
+      if (givesCheck && pos.see_sign(move) >= 0)
           ext = ONE_PLY;
 
-      else if (givesCheck && pos.see_sign(move) >= 0)
-          ext = inCheck || ss->staticEval <= alpha ? ONE_PLY : ONE_PLY / 2;
-
       // Singular extension search. If all moves but one fail low on a search of
       // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
       // is singular and should be extended. To verify this we do a reduced search
@@ -951,8 +945,11 @@ moves_loop: // When in check and at SpNode search starts from here
           if (!PvNode && cutNode)
               ss->reduction += ONE_PLY;
 
+          else if (History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
+              ss->reduction += ONE_PLY / 2;
+
           if (move == countermoves[0] || move == countermoves[1])
-              ss->reduction = std::max(DEPTH_ZERO, ss->reduction-ONE_PLY);
+              ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
 
           Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
           if (SpNode)
@@ -1104,7 +1101,7 @@ moves_loop: // When in check and at SpNode search starts from here
         // played non-capture moves.
         Value bonus = Value(int(depth) * int(depth));
         History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
-        for (int i = 0; i < quietCount - 1; i++)
+        for (int i = 0; i < quietCount - 1; ++i)
         {
             Move m = quietsSearched[i];
             History.update(pos.piece_moved(m), to_sq(m), -bonus);
@@ -1458,7 +1455,7 @@ moves_loop: // When in check and at SpNode search starts from here
     // Choose best move. For each move score we add two terms both dependent on
     // weakness, one deterministic and bigger for weaker moves, and one random,
     // then we choose the move with the resulting highest score.
-    for (size_t i = 0; i < PVSize; i++)
+    for (size_t i = 0; i < PVSize; ++i)
     {
         int s = RootMoves[i].score;
 
@@ -1491,11 +1488,11 @@ moves_loop: // When in check and at SpNode search starts from here
     size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
     int selDepth = 0;
 
-    for (size_t i = 0; i < Threads.size(); i++)
+    for (size_t i = 0; i < Threads.size(); ++i)
         if (Threads[i]->maxPly > selDepth)
             selDepth = Threads[i]->maxPly;
 
-    for (size_t i = 0; i < uciPVSize; i++)
+    for (size_t i = 0; i < uciPVSize; ++i)
     {
         bool updated = (i <= PVIdx);
 
@@ -1732,7 +1729,7 @@ void check_time() {
 
       // Loop across all split points and sum accumulated SplitPoint nodes plus
       // all the currently active positions nodes.
-      for (size_t i = 0; i < Threads.size(); i++)
+      for (size_t i = 0; i < Threads.size(); ++i)
           for (int j = 0; j < Threads[i]->splitPointsSize; j++)
           {
               SplitPoint& sp = Threads[i]->splitPoints[j];