Synchronize pruning rules in search and sp_search

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 96a945e666ed66b8d54acca97791cd37f1d665c5..0fe242dd120f9afe15a827c1d8a0b0805640d1e7 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -288,7 +288,7 @@ namespace {
   bool move_is_killer(Move m, const SearchStack& ss);
   Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
   bool ok_to_do_nullmove(const Position& pos);
-  bool ok_to_prune(const Position& pos, Move m, Move threat, Depth d);
+  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);
   void update_history(const Position& pos, Move m, Depth depth, Move movesSearched[], int moveCount);
   void update_killers(Move m, SearchStack& ss);
@@ -1510,9 +1510,9 @@ namespace {
           && !captureOrPromotion
           &&  move != ttMove)
       {
-          // History pruning. See ok_to_prune() definition
+          // Move count based pruning
           if (   moveCount >= FutilityMoveCountMargin
-              && ok_to_prune(pos, move, ss[ply].threatMove, depth)
+              && ok_to_prune(pos, move, ss[ply].threatMove)
               && bestValue > value_mated_in(PLY_MAX))
               continue;
 
@@ -1814,6 +1814,7 @@ namespace {
     bool useFutilityPruning =     sp->depth < SelectiveDepth
                               && !isCheck;
 
+    const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
     const int FutilityValueMargin = 112 * bitScanReverse32(int(sp->depth) * int(sp->depth) / 2);
 
     while (    sp->bestValue < sp->beta
@@ -1841,32 +1842,31 @@ namespace {
           && !dangerous
           && !captureOrPromotion)
       {
-          // History pruning. See ok_to_prune() definition
-          if (   moveCount >= 2 + int(sp->depth)
-              && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth)
+          // Move count based pruning
+          if (   moveCount >= FutilityMoveCountMargin
+              && ok_to_prune(pos, move, ss[sp->ply].threatMove)
               && sp->bestValue > value_mated_in(PLY_MAX))
               continue;
 
           // Value based pruning
-          if (sp->approximateEval < sp->beta)
+          if (sp->futilityValue == VALUE_NONE)
           {
-              if (sp->futilityValue == VALUE_NONE)
-              {
-                  EvalInfo ei;
-                  sp->futilityValue = evaluate(pos, ei, threadID) + FutilityValueMargin;
-              }
+              EvalInfo ei;
+              sp->futilityValue = evaluate(pos, ei, threadID) + FutilityValueMargin;
+          }
+
+          Value futilityValueScaled = sp->futilityValue - moveCount * IncrementalFutilityMargin;
 
-              if (sp->futilityValue < sp->beta)
+          if (futilityValueScaled < sp->beta)
+          {
+              if (futilityValueScaled > sp->bestValue) // Less then 1% of cases
               {
-                  if (sp->futilityValue > sp->bestValue) // Less then 1% of cases
-                  {
-                      lock_grab(&(sp->lock));
-                      if (sp->futilityValue > sp->bestValue)
-                          sp->bestValue = sp->futilityValue;
-                      lock_release(&(sp->lock));
-                  }
-                  continue;
+                  lock_grab(&(sp->lock));
+                  if (futilityValueScaled > sp->bestValue)
+                      sp->bestValue = futilityValueScaled;
+                  lock_release(&(sp->lock));
               }
+              continue;
           }
       }
 
@@ -2464,7 +2464,7 @@ namespace {
   // non-tactical moves late in the move list close to the leaves are
   // candidates for pruning.
 
-  bool ok_to_prune(const Position& pos, Move m, Move threat, Depth d) {
+  bool ok_to_prune(const Position& pos, Move m, Move threat) {
 
     assert(move_is_ok(m));
     assert(threat == MOVE_NONE || move_is_ok(threat));
@@ -2498,11 +2498,7 @@ namespace {
         && pos.move_attacks_square(m, tto))
         return false;
 
-    // Case 4: Don't prune moves with good history
-    if (!H.ok_to_prune(pos.piece_on(mfrom), mto, d))
-        return false;
-
-    // Case 5: If the moving piece in the threatened move is a slider, don't
+    // Case 4: If the moving piece in the threatened move is a slider, don't
     // prune safe moves which block its ray.
     if (  !PruneBlockingMoves
         && threat != MOVE_NONE
@@ -2543,7 +2539,7 @@ namespace {
     {
         assert(m != movesSearched[i]);
         if (!pos.move_is_capture_or_promotion(movesSearched[i]))
-            H.failure(pos.piece_on(move_from(movesSearched[i])), move_to(movesSearched[i]));
+            H.failure(pos.piece_on(move_from(movesSearched[i])), move_to(movesSearched[i]), depth);
     }
   }