Singular extension and check extension tweak

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cb16798dc427fcc30162a9f346c0402aac680a95..7029ae032ef8ba2703a7fa5080f4f319628fcf46 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -82,7 +82,7 @@ namespace {
   // History and stats update bonus, based on depth
   Value stat_bonus(Depth depth) {
     int d = depth / ONE_PLY ;
-    return Value(d * d + 2 * d - 2);
+    return d > 17 ? VALUE_ZERO : Value(d * d + 2 * d - 2);
   }
 
   // Skill structure is used to implement strength limit
@@ -163,7 +163,7 @@ void Search::init() {
       for (int d = 1; d < 64; ++d)
           for (int mc = 1; mc < 64; ++mc)
           {
-              double r = log(d) * log(mc) / 2;
+              double r = log(d) * log(mc) / 1.95;
 
               Reductions[NonPV][imp][d][mc] = int(std::round(r));
               Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
@@ -542,7 +542,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;
     Piece moved_piece;
     int moveCount, quietCount;
 
@@ -829,10 +829,11 @@ moves_loop: // When in check search starts from here
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
+    skipQuiets = false;
 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
-    while ((move = mp.next_move()) != MOVE_NONE)
+    while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
     {
       assert(is_ok(move));
 
@@ -867,12 +868,7 @@ moves_loop: // When in check search starts from here
       moveCountPruning =   depth < 16 * ONE_PLY
                         && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
 
-      // Step 12. Extensions
-      // Extend checks
-      if (    givesCheck
-          && !moveCountPruning
-          &&  pos.see_ge(move, VALUE_ZERO))
-          extension = ONE_PLY;
+      // Step 12. Singular and Gives Check Extensions
 
       // Singular extension search. If all moves but one fail low on a search of
       // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
@@ -881,7 +877,6 @@ moves_loop: // When in check search starts from here
       // ttValue minus a margin then we extend the ttMove.
       if (    singularExtensionNode
           &&  move == ttMove
-          && !extension
           &&  pos.legal(move))
       {
           Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
@@ -893,6 +888,10 @@ moves_loop: // When in check search starts from here
           if (value < rBeta)
               extension = ONE_PLY;
       }
+      else if (   givesCheck
+               && !moveCountPruning
+               &&  pos.see_ge(move, VALUE_ZERO))
+          extension = ONE_PLY;
 
       // Calculate new depth for this move
       newDepth = depth - ONE_PLY + extension;
@@ -906,8 +905,10 @@ moves_loop: // When in check search starts from here
               && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= 5000))
           {
               // Move count based pruning
-              if (moveCountPruning)
+              if (moveCountPruning) {
+                  skipQuiets = true;
                   continue;
+              }
 
               // Reduced depth of the next LMR search
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;