Futility tweak

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d1b717b47124fece1fc71255ad68f6a4da90f2e7..64e9028b10bd82fd1c7bc2d77e52bb960f17048f 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -65,7 +65,7 @@ namespace {
 
   // Razoring and futility margin based on depth
   const int razor_margin[4] = { 483, 570, 603, 554 };
-  Value futility_margin(Depth d) { return Value(200 * d); }
+  Value futility_margin(Depth d) { return Value(150 * d); }
 
   // Futility and reductions lookup tables, initialized at startup
   int FutilityMoveCounts[2][16];  // [improving][depth]
@@ -549,6 +549,7 @@ namespace {
     assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
     assert(PvNode || (alpha == beta - 1));
     assert(DEPTH_ZERO < depth && depth < DEPTH_MAX);
+    assert(!(PvNode && cutNode));
 
     Move pv[MAX_PLY+1], quietsSearched[64];
     StateInfo st;
@@ -728,8 +729,8 @@ namespace {
 
     // Step 8. Null move search with verification search (is omitted in PV nodes)
     if (   !PvNode
-        &&  depth >= 2 * ONE_PLY
         &&  eval >= beta
+        && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
         &&  pos.non_pawn_material(pos.side_to_move()))
     {
         ss->currentMove = MOVE_NULL;
@@ -814,7 +815,6 @@ namespace {
 
 moves_loop: // When in check search starts from here
 
-    Square prevSq = to_sq((ss-1)->currentMove);
     const CounterMoveStats* cmh  = (ss-1)->counterMoves;
     const CounterMoveStats* fmh  = (ss-2)->counterMoves;
     const CounterMoveStats* fmh2 = (ss-4)->counterMoves;
@@ -823,7 +823,7 @@ moves_loop: // When in check search starts from here
     CheckInfo ci(pos);
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
     improving =   ss->staticEval >= (ss-2)->staticEval
-               || ss->staticEval == VALUE_NONE
+            /* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */
                ||(ss-2)->staticEval == VALUE_NONE;
 
     singularExtensionNode =   !rootNode
@@ -926,12 +926,19 @@ moves_loop: // When in check search starts from here
 
           // Futility pruning: parent node
           if (   predictedDepth < 7 * ONE_PLY
-              && ss->staticEval + futility_margin(predictedDepth) + 256 <= alpha)
+              && ss->staticEval + 256 + 200 * predictedDepth / ONE_PLY <= alpha)
               continue;
 
-          // Prune moves with negative SEE at low depths
-          if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
-              continue;
+          // Prune moves with negative SEE at low depths and below a decreasing
+          // threshold at higher depths.
+          if (predictedDepth < 8 * ONE_PLY)
+          {
+              Value see_v = predictedDepth < 4 * ONE_PLY ? VALUE_ZERO
+                            : -PawnValueMg * 2 * int(predictedDepth - 3 * ONE_PLY);
+
+              if (pos.see_sign(move) < see_v)
+                  continue;
+          }
       }
 
       // Speculative prefetch as early as possible
@@ -963,7 +970,7 @@ moves_loop: // When in check search starts from here
                      +    (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO);
 
           // Increase reduction for cut nodes
-          if (!PvNode && cutNode)
+          if (cutNode)
               r += 2 * ONE_PLY;
 
           // Decrease reduction for moves that escape a capture. Filter out
@@ -1105,10 +1112,10 @@ moves_loop: // When in check search starts from here
     // Bonus for prior countermove that caused the fail low
     else if (    depth >= 3 * ONE_PLY
              && !bestMove
-             && !inCheck
              && !pos.captured_piece_type()
              && is_ok((ss-1)->currentMove))
     {
+        Square prevSq = to_sq((ss-1)->currentMove);
         Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + 2 * depth / ONE_PLY - 2);
         if ((ss-2)->counterMoves)
             (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);
@@ -1573,16 +1580,16 @@ bool RootMove::extract_ponder_from_tt(Position& pos)
 
     pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos)));
     TTEntry* tte = TT.probe(pos.key(), ttHit);
-    pos.undo_move(pv[0]);
 
     if (ttHit)
     {
         Move m = tte->move(); // Local copy to be SMP safe
         if (MoveList<LEGAL>(pos).contains(m))
-           return pv.push_back(m), true;
+            pv.push_back(m);
     }
 
-    return false;
+    pos.undo_move(pv[0]);
+    return pv.size() > 1;
 }
 
 void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) {