Retire eval optimization from null search

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 35160b9665a39d6ed99bae69da65940ebf9f049b..b538897944ba7d174e17fdded262d8ddb719f0f4 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -62,10 +62,6 @@ namespace {
   // Different node types, used as template parameter
   enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
 
-  // Lookup table to check if a Piece is a slider and its access function
-  const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
-  inline bool piece_is_slider(Piece p) { return Slidings[p]; }
-
   // Dynamic razoring margin based on depth
   inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
 
@@ -222,7 +218,7 @@ void Search::think() {
   if (Options["Use Search Log"])
   {
       Log log(Options["Search Log Filename"]);
-      log << "\nSearching: "  << RootPos.to_fen()
+      log << "\nSearching: "  << RootPos.fen()
           << "\ninfinite: "   << Limits.infinite
           << " ponder: "      << Limits.ponder
           << " time: "        << Limits.time[RootColor]
@@ -395,7 +391,8 @@ namespace {
 
             // Sort the PV lines searched so far and update the GUI
             sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
-            sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+            if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000)
+                sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
         }
 
         // Do we need to pick now the sub-optimal best move ?
@@ -797,7 +794,7 @@ split_point_start: // At split points actual search starts from here
       {
           Signals.firstRootMove = (moveCount == 1);
 
-          if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000)
+          if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000)
               sync_cout << "info depth " << depth / ONE_PLY
                         << " currmove " << move_to_uci(move, pos.is_chess960())
                         << " currmovenumber " << moveCount + PVIdx << sync_endl;
@@ -896,7 +893,7 @@ split_point_start: // At split points actual search starts from here
       }
 
       // Check for legality only before to do the move
-      if (!pos.pl_move_is_legal(move, ci.pinned))
+      if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned))
       {
           moveCount--;
           continue;
@@ -1007,8 +1004,10 @@ split_point_start: // At split points actual search starts from here
                   alpha = value; // Update alpha here! Always alpha < beta
                   if (SpNode) sp->alpha = value;
               }
-              else // Fail high
+              else
               {
+                  assert(value >= beta); // Fail high
+
                   if (SpNode) sp->cutoff = true;
                   break;
               }
@@ -1020,8 +1019,12 @@ split_point_start: // At split points actual search starts from here
           &&  depth >= Threads.min_split_depth()
           &&  bestValue < beta
           &&  Threads.available_slave_exists(thisThread))
+      {
           bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
                                                depth, threatMove, moveCount, mp, NT);
+          if (bestValue >= beta)
+              break;
+      }
     }
 
     if (SpNode)
@@ -1101,10 +1104,14 @@ split_point_start: // At split points actual search starts from here
     const TTEntry* tte;
     Key posKey;
     Move ttMove, move, bestMove;
-    Value bestValue, value, ttValue, futilityValue, futilityBase;
+    Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
     bool givesCheck, enoughMaterial, evasionPrunable;
     Depth ttDepth;
 
+    // To flag BOUND_EXACT a node with eval above alpha and no available moves
+    if (PvNode)
+        oldAlpha = alpha;
+
     ss->currentMove = bestMove = MOVE_NONE;
     ss->ply = (ss-1)->ply + 1;
 
@@ -1203,9 +1210,7 @@ split_point_start: // At split points actual search starts from here
 
           if (futilityValue < beta)
           {
-              if (futilityValue > bestValue)
-                  bestValue = futilityValue;
-
+              bestValue = std::max(bestValue, futilityValue);
               continue;
           }
 
@@ -1213,7 +1218,10 @@ split_point_start: // At split points actual search starts from here
           if (   futilityBase < beta
               && depth < DEPTH_ZERO
               && pos.see(move) <= 0)
+          {
+              bestValue = std::max(bestValue, futilityBase);
               continue;
+          }
       }
 
       // Detect non-capture evasions that are candidate to be pruned
@@ -1284,7 +1292,7 @@ split_point_start: // At split points actual search starts from here
         return mated_in(ss->ply); // Plies to mate from the root
 
     TT.store(posKey, value_to_tt(bestValue, ss->ply),
-             PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+             PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
              ttDepth, bestMove, ss->staticEval, ss->evalMargin);
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
@@ -1437,10 +1445,8 @@ split_point_start: // At split points actual search starts from here
             return true;
     }
 
-    // If the threat piece is a slider, don't prune safe moves which block it
-    if (    piece_is_slider(pos.piece_on(tfrom))
-        && (between_bb(tfrom, tto) & mto)
-        &&  pos.see_sign(move) >= 0)
+    // Don't prune safe moves which block the threat path
+    if ((between_bb(tfrom, tto) & mto) && pos.see_sign(move) >= 0)
         return true;
 
     return false;