Fix random moves when time < 10ms

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c9f1aee0685be46653a04758ed1693ef6f6f1995..4b0a9fe8b60676b96c7c5dcc9bda19f9d5bcd6b8 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -242,13 +242,11 @@ void Search::think() {
   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.
+  // 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.
   Threads.timer->msec =
   Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) :
-                  Limits.nodes ? 2 * TimerResolution
-                               : 100;
-
-  Threads.timer->notify_one(); // Wake up the recurring timer
+                  Limits.nodes ? 2 * TimerResolution : 100;
 
   id_loop(RootPos); // Let's start searching !
 
@@ -333,7 +331,7 @@ namespace {
     while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
     {
         // Age out PV variability metric
-        BestMoveChanges *= 0.8;
+        BestMoveChanges *= 0.8f;
 
         // 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.
@@ -402,6 +400,10 @@ 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);
 
@@ -780,7 +782,7 @@ moves_loop: // When in check and at SpNode search starts from here
 
     singularExtensionNode =   !RootNode
                            && !SpNode
-                           &&  depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
+                           &&  depth >= 8 * ONE_PLY
                            &&  ttMove != MOVE_NONE
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
@@ -937,7 +939,7 @@ moves_loop: // When in check and at SpNode search starts from here
 
       // Step 15. Reduced depth search (LMR). If the move fails high will be
       // re-searched at full depth.
-      if (    depth > 3 * ONE_PLY
+      if (    depth >= 3 * ONE_PLY
           && !pvMove
           && !captureOrPromotion
           &&  move != ttMove
@@ -1361,7 +1363,10 @@ moves_loop: // When in check and at SpNode search starts from here
     Square m2to = to_sq(second);
 
     // The piece is the same or second's destination was vacated by the first move
-    if (m1to == m2from || m2to == m1from)
+    // We exclude the trivial case where a sliding piece does in two moves what
+    // it could do in one move: eg. Ra1a2, Ra2a3.
+    if (    m2to == m1from
+        || (m1to == m2from && !squares_aligned(m1from, m2from, m2to)))
         return true;
 
     // Second one moves through the square vacated by first one