Use TT refined value to stand pat

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index dcf3e6134a4a5d4c83c48a1542f85f8ec3ebb23f..4683a006ffe42c93f613a384f83df61b26418bcf 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -84,7 +84,7 @@ namespace {
 
   size_t PVSize, PVIdx;
   TimeManager TimeMgr;
-  float BestMoveChanges;
+  double BestMoveChanges;
   Value DrawValue[COLOR_NB];
   HistoryStats History;
   GainsStats Gains;
@@ -333,7 +333,7 @@ namespace {
     while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
     {
         // Age out PV variability metric
-        BestMoveChanges *= 0.8f;
+        BestMoveChanges *= 0.8;
 
         // 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.
@@ -1188,6 +1188,11 @@ moves_loop: // When in check and at SpNode search starts from here
             if (  (ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE
                 ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE)
                 ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
+
+            // Can ttValue be used as a better position evaluation?
+            if (ttValue != VALUE_NONE)
+                if (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER))
+                    bestValue = ttValue;
         }
         else
             ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
@@ -1205,7 +1210,7 @@ moves_loop: // When in check and at SpNode search starts from here
         if (PvNode && bestValue > alpha)
             alpha = bestValue;
 
-        futilityBase = ss->staticEval + ss->evalMargin + Value(128);
+        futilityBase = bestValue + ss->evalMargin + Value(128);
     }
 
     // Initialize a MovePicker object for the current position, and prepare