Retire easy move

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 7075c3373a2c90eec8a021e45d8552544f529ab7..be82568a2179f03eb9bce512617950a7abad8f50 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -43,7 +43,7 @@ namespace Search {
   std::vector<RootMove> RootMoves;
   Position RootPos;
   Color RootColor;
-  Time::point SearchTime;
+  Time::point SearchTime, IterationTime;
   StateStackPtr SetupStates;
 }
 
@@ -396,6 +396,8 @@ namespace {
                 sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
         }
 
+        IterationTime = Time::now() - SearchTime;
+
         // If skill levels are enabled and time is up, pick a sub-optimal best move
         if (skill.enabled() && skill.time_to_pick(depth))
             skill.pick_move();
@@ -426,32 +428,13 @@ namespace {
             if (depth > 4 && depth < 50 &&  PVSize == 1)
                 TimeMgr.pv_instability(BestMoveChanges);
 
-            // Stop the search if most of the available time has been used. We
-            // probably don't have enough time to search the first move at the
-            // next iteration anyway.
-            if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
+            // Stop the search if only one legal move is available or most
+            // of the available time has been used. We probably don't have
+            // enough time to search the first move at the next iteration anyway.
+            if (   RootMoves.size() == 1
+                || IterationTime > (TimeMgr.available_time() * 62) / 100)
                 stop = true;
 
-            // Stop the search early if one move seems to be much better than others
-            if (    depth >= 12
-                &&  BestMoveChanges <= DBL_EPSILON
-                && !stop
-                &&  PVSize == 1
-                &&  bestValue > VALUE_MATED_IN_MAX_PLY
-                && (   RootMoves.size() == 1
-                    || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100))
-            {
-                Value rBeta = bestValue - 2 * PawnValueMg;
-                ss->excludedMove = RootMoves[0].pv[0];
-                ss->skipNullMove = true;
-                Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true);
-                ss->skipNullMove = false;
-                ss->excludedMove = MOVE_NONE;
-
-                if (v < rBeta)
-                    stop = true;
-            }
-
             if (stop)
             {
                 // If we are allowed to ponder do not stop the search now but
@@ -1629,7 +1612,8 @@ void check_time() {
   Time::point elapsed = Time::now() - SearchTime;
   bool stillAtFirstMove =    Signals.firstRootMove
                          && !Signals.failedLowAtRoot
-                         &&  elapsed > TimeMgr.available_time();
+                         &&  elapsed > (TimeMgr.available_time() * 62) / 100
+                         &&  elapsed > IterationTime * 1.4;
 
   bool noMoreTime =   elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
                    || stillAtFirstMove;