Remove useless variable 'PostFutilityValueMargin'

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c894403cc452337c87abfc2d3cd99227b892a645..7b9b5b370b5aac62a916e6dcb3d020dbaa065e10 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -185,6 +185,8 @@ namespace {
   // and near frontier nodes.
   const Value FutilityMarginQS = Value(0x80);
 
+  Value FutilityMargins[2 * PLY_MAX_PLUS_2]; // Initialized at startup.
+
   // Each move futility margin is decreased
   const Value IncrementalFutilityMargin = Value(0x8);
 
@@ -286,6 +288,7 @@ namespace {
   bool ok_to_prune(const Position& pos, Move m, Move threat);
   bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
   Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
+  Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor);
   void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
   void update_killers(Move m, SearchStack& ss);
   void update_gains(const Position& pos, Move move, Value before, Value after);
@@ -575,6 +578,14 @@ void init_threads() {
   for (i = 0; i < THREAD_MAX; i++)
       Threads[i].activeSplitPoints = 0;
 
+  // Init futility margins array
+  FutilityMargins[0] = FutilityMargins[1] = Value(0);
+
+  for (i = 2; i < 2 * PLY_MAX_PLUS_2; i++)
+  {
+      FutilityMargins[i] = Value(112 * bitScanReverse32(i * i / 2)); // FIXME: test using log instead of BSR
+  }
+
   // Initialize global locks
   lock_init(&MPLock, NULL);
   lock_init(&IOLock, NULL);
@@ -988,10 +999,9 @@ namespace {
                 && !captureOrPromotion
                 && !move_is_castle(move))
             {
-                double red = 0.5 + ln(RootMoveNumber - MultiPV + 1) * ln(depth / 2) / 6.0;
-                if (red >= 1.0)
+                ss[0].reduction = calculate_reduction(0.5, RootMoveNumber - MultiPV + 1, depth, 6.0);
+                if (ss[0].reduction)
                 {
-                    ss[0].reduction = Depth(int(floor(red * int(OnePly))));
                     value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
                     doFullDepthSearch = (value > alpha);
                 }
@@ -999,6 +1009,7 @@ namespace {
 
             if (doFullDepthSearch)
             {
+                ss[0].reduction = Depth(0);
                 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
 
                 if (value > alpha)
@@ -1301,13 +1312,12 @@ namespace {
             && !move_is_castle(move)
             && !move_is_killer(move, ss[ply]))
         {
-          double red = 0.5 + ln(moveCount) * ln(depth / 2) / 6.0;
-          if (red >= 1.0)
-          {
-              ss[ply].reduction = Depth(int(floor(red * int(OnePly))));
-              value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
-              doFullDepthSearch = (value > alpha);
-          }
+            ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 6.0);
+            if (ss[ply].reduction)
+            {
+                value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
+                doFullDepthSearch = (value > alpha);
+            }
         }
 
         if (doFullDepthSearch) // Go with full depth non-pv search
@@ -1458,7 +1468,6 @@ namespace {
 
     // Calculate depth dependant futility pruning parameters
     const int FutilityMoveCountMargin = 3 + (1 << (3 * int(depth) / 8));
-    const int PostFutilityValueMargin = 112 * bitScanReverse32(int(depth) * int(depth) / 2);
 
     // Evaluate the position statically
     if (!isCheck)
@@ -1472,7 +1481,7 @@ namespace {
         }
 
         ss[ply].eval = staticValue;
-        futilityValue = staticValue + PostFutilityValueMargin; //FIXME: Remove me, only for split
+        futilityValue = staticValue + FutilityMargins[int(depth)]; //FIXME: Remove me, only for split
         staticValue = refine_eval(tte, staticValue, ply); // Enhance accuracy with TT value if possible
         update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
     }
@@ -1483,8 +1492,8 @@ namespace {
     // FIXME: test with modified condition 'depth < RazorDepth'
     if (  !isCheck
         && depth < SelectiveDepth
-        && staticValue - PostFutilityValueMargin >= beta)
-        return staticValue - PostFutilityValueMargin;
+        && staticValue - FutilityMargins[int(depth)] >= beta)
+        return staticValue - FutilityMargins[int(depth)];
 
     // Null move search
     if (    allowNullmove
@@ -1626,7 +1635,7 @@ namespace {
           int preFutilityValueMargin = 0;
 
           if (newDepth >= OnePly)
-              preFutilityValueMargin = 112 * bitScanReverse32(int(newDepth) * int(newDepth) / 2);
+              preFutilityValueMargin = FutilityMargins[int(newDepth)];
 
           Value futilityCaptureValue = ss[ply].eval + pos.endgame_value_of_piece_on(move_to(move)) + preFutilityValueMargin + ei.futilityMargin + 90;
 
@@ -1654,16 +1663,16 @@ namespace {
           // Value based pruning
           Depth predictedDepth = newDepth;
 
-          //FIXME HACK: awful code duplication
-          double red = 0.5 + ln(moveCount) * ln(depth / 2) / 3.0;
-          if (red >= 1.0)
-              predictedDepth -= int(floor(red * int(OnePly)));
+          //FIXME: We are ignoring condition: depth >= 3*OnePly, BUG??
+          ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 3.0);
+          if (ss[ply].reduction)
+              predictedDepth -= ss[ply].reduction;
 
           if (predictedDepth < SelectiveDepth)
           {
               int preFutilityValueMargin = 0;
               if (predictedDepth >= OnePly)
-                  preFutilityValueMargin = 112 * bitScanReverse32(int(predictedDepth) * int(predictedDepth) / 2);
+                  preFutilityValueMargin = FutilityMargins[int(predictedDepth)];
 
               preFutilityValueMargin += H.gain(pos.piece_on(move_from(move)), move_from(move), move_to(move)) + 45;
 
@@ -1689,13 +1698,11 @@ namespace {
           && !dangerous
           && !captureOrPromotion
           && !move_is_castle(move)
-          && !move_is_killer(move, ss[ply])
-          /* && move != ttMove*/)
+          && !move_is_killer(move, ss[ply]))
       {
-          double red = 0.5 + ln(moveCount) * ln(depth / 2) / 3.0;
-          if (red >= 1.0)
+          ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 3.0);
+          if (ss[ply].reduction)
           {
-              ss[ply].reduction = Depth(int(floor(red * int(OnePly))));
               value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
               doFullDepthSearch = (value >= beta);
           }
@@ -2037,10 +2044,9 @@ namespace {
           && !move_is_castle(move)
           && !move_is_killer(move, ss[sp->ply]))
       {
-          double red = 0.5 + ln(moveCount) * ln(sp->depth / 2) / 3.0;
-          if (red >= 1.0)
+          ss[sp->ply].reduction = calculate_reduction(0.5, moveCount, sp->depth, 3.0);
+          if (ss[sp->ply].reduction)
           {
-              ss[sp->ply].reduction = Depth(int(floor(red * int(OnePly))));
               value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
               doFullDepthSearch = (value >= sp->beta);
           }
@@ -2151,11 +2157,10 @@ namespace {
           && !move_is_castle(move)
           && !move_is_killer(move, ss[sp->ply]))
       {
-          double red = 0.5 + ln(moveCount) * ln(sp->depth / 2) / 6.0;
-          if (red >= 1.0)
+          ss[sp->ply].reduction = calculate_reduction(0.5, moveCount, sp->depth, 6.0);
+          if (ss[sp->ply].reduction)
           {
               Value localAlpha = sp->alpha;
-              ss[sp->ply].reduction = Depth(int(floor(red * int(OnePly))));
               value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
               doFullDepthSearch = (value > localAlpha);
           }
@@ -2679,6 +2684,20 @@ namespace {
       return defaultEval;
   }
 
+  // calculate_reduction() returns reduction in plies based on
+  // moveCount and depth. Reduction is always at least one ply.
+
+  Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor) {
+
+    double red = baseReduction + ln(moveCount) * ln(depth / 2) / reductionInhibitor;
+
+    if (red >= 1.0)
+        return Depth(int(floor(red * int(OnePly))));
+    else
+        return Depth(0);
+
+  }
+
   // update_history() registers a good move that produced a beta-cutoff
   // in history and marks as failures all the other moves of that ply.