Remove 4*IncrementalFutilityMargin from futilityValue

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d654fec9c414a75be3fd6d406fdaf8fc24053613..faac36ce966727734c0109bf42fda9ef20dac9c1 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -176,6 +176,9 @@ namespace {
   // and near frontier nodes.
   const Value FutilityMarginQS = Value(0x80);
 
+  // Each move futility margin is decreased
+  const Value IncrementalFutilityMargin = Value(0xA);
+
   // Remaining depth:                  1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
   const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270),
   //                                   4 ply         4.5 ply       5 ply         5.5 ply       6 ply         6.5 ply
@@ -1260,7 +1263,7 @@ namespace {
     const TTEntry* tte;
     Move ttMove, move;
     Depth ext, newDepth;
-    Value approximateEval, nullValue, value, futilityValue;
+    Value approximateEval, nullValue, value, futilityValue, futilityValueScaled;
     bool isCheck, useFutilityPruning, singleReply, moveIsCheck, captureOrPromotion, dangerous;
     bool mateThreat = false;
     int moveCount = 0;
@@ -1314,7 +1317,13 @@ namespace {
         ss[ply].currentMove = MOVE_NULL;
 
         pos.do_null_move(st);
-        int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
+
+        // Null move dynamic reduction based on depth
+        int R = (depth >= 5 * OnePly ? 4 : 3);
+
+        // Null move dynamic reduction based on value
+        if (approximateEval - beta > PawnValueMidgame)
+            R++;
 
         nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
 
@@ -1354,8 +1363,9 @@ namespace {
              && ttMove == MOVE_NONE
              && !pos.has_pawn_on_7th(pos.side_to_move()))
     {
-        Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
-        if (v < beta - RazorMargins[int(depth) - 2])
+        Value rbeta = beta - RazorMargins[int(depth) - 2];
+        Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
+        if (v < rbeta)
           return v;
     }
 
@@ -1378,6 +1388,9 @@ namespace {
     if (tte && (tte->type() & VALUE_TYPE_EVAL))
         futilityValue = value_from_tt(tte->value(), ply) + FutilityMargins[int(depth) - 2];
 
+    // Move count pruning limit
+    const int MCLimit = 3 + (1 << (3*int(depth)/8));
+
     // Loop through all legal moves until no moves remain or a beta cutoff
     // occurs.
     while (   bestValue < beta
@@ -1402,8 +1415,55 @@ namespace {
           && !captureOrPromotion
           &&  move != ttMove)
       {
+          //std::cout << std::endl;
+          //for (int d = 2; d < 14; d++)
+          //    std::cout << d << ", " << 64*(1+bitScanReverse32(d*d)) << std::endl;
+
+          //std::cout << std::endl;
+/*
+            64*(1+bitScanReverse32(d*d))
+
+            2 -> 256 -  256
+            3 -> 288 -  320
+            4 -> 512 -  384
+            5 -> 544 -  384
+            6 -> 592 -  448
+            7 -> 624 -  448
+            8 -> 672 -  512
+            9 -> 704 -  512
+           10 -> 832 -  512
+           11 -> 864 -  512
+           12 -> 928 -  576
+           13 -> 960 -  576
+
+            300 + 2*(1 << (3*d/4))
+
+            2 -> 256 -  304
+            3 -> 288 -  308
+            4 -> 512 -  316
+            5 -> 544 -  316
+            6 -> 592 -  332
+            7 -> 624 -  364
+            8 -> 672 -  428
+            9 -> 704 -  428
+           10 -> 832 -  556
+           11 -> 864 -  812
+           12 -> 928 -  1324
+           13 -> 960 -  1324
+
+
+            3 + (1 << (3*int(depth)/8))
+
+            1 * onePly - > moveCount >= 4
+            2 * onePly - > moveCount >= 5
+            3 * onePly - > moveCount >= 7
+            4 * onePly - > moveCount >= 11
+            5 * onePly - > moveCount >= 11
+            6 * onePly - > moveCount >= 19
+            7 * onePly - > moveCount >= 35
+*/
           // History pruning. See ok_to_prune() definition
-          if (   moveCount >= 2 + int(depth)
+          if (   moveCount >= MCLimit
               && ok_to_prune(pos, move, ss[ply].threatMove, depth)
               && bestValue > value_mated_in(PLY_MAX))
               continue;
@@ -1413,12 +1473,14 @@ namespace {
           {
               if (futilityValue == VALUE_NONE)
                   futilityValue =  evaluate(pos, ei, threadID)
-                                 + FutilityMargins[int(depth) - 2];
+                                 + 64*(1+bitScanReverse32(int(depth) * int(depth)));
+
+              futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin;
 
-              if (futilityValue < beta)
+              if (futilityValueScaled < beta)
               {
-                  if (futilityValue > bestValue)
-                      bestValue = futilityValue;
+                  if (futilityValueScaled > bestValue)
+                      bestValue = futilityValueScaled;
                   continue;
               }
           }