Simplify futility margins formula

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index dcf3e6134a4a5d4c83c48a1542f85f8ec3ebb23f..442f7f5ddc3e4fda6592ac903407d3f4f04550a4 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;
@@ -143,11 +143,14 @@ void Search::init() {
 
       if (Reductions[0][0][hd][mc] > 2 * ONE_PLY)
           Reductions[0][0][hd][mc] += ONE_PLY;
+
+      else if (Reductions[0][0][hd][mc] > 1 * ONE_PLY)
+          Reductions[0][0][hd][mc] += ONE_PLY / 2;
   }
 
   // Init futility margins array
   for (d = 1; d < 16; ++d) for (mc = 0; mc < 64; ++mc)
-      FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
+      FutilityMargins[d][mc] = Value(112 * int(2.9 * log(double(d))) - 8 * mc + 45);
 
   // Init futility move count array
   for (d = 0; d < 32; ++d)
@@ -333,7 +336,7 @@ 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 +1191,11 @@ 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 +1213,7 @@ 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