Fix Singular extension condition to handle mate scores

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cb502f077109ef58c3500ea2c3cd0bdbd24a66cb..8f9a369ae23d86a9a4d62d046a8f35ea4c9f6013 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -42,7 +42,6 @@ namespace Search {
   LimitsType Limits;
   std::vector<RootMove> RootMoves;
   Position RootPos;
-  Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
 }
@@ -180,12 +179,11 @@ uint64_t Search::perft(Position& pos, Depth depth) {
 
 void Search::think() {
 
-  RootColor = RootPos.side_to_move();
-  TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
+  TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
 
   int cf = Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
-  DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
-  DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
+  DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf);
+  DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf);
 
   if (RootMoves.empty())
   {
@@ -203,8 +201,8 @@ void Search::think() {
       log << "\nSearching: "  << RootPos.fen()
           << "\ninfinite: "   << Limits.infinite
           << " ponder: "      << Limits.ponder
-          << " time: "        << Limits.time[RootColor]
-          << " increment: "   << Limits.inc[RootColor]
+          << " time: "        << Limits.time[RootPos.side_to_move()]
+          << " increment: "   << Limits.inc[RootPos.side_to_move()]
           << " moves to go: " << Limits.movestogo
           << "\n" << std::endl;
   }
@@ -272,7 +270,6 @@ namespace {
     Value bestValue, alpha, beta, delta;
 
     std::memset(ss-2, 0, 5 * sizeof(Stack));
-    (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
 
     depth = 0;
     BestMoveChanges = 0;
@@ -547,7 +544,9 @@ namespace {
     }
     else
     {
-        eval = ss->staticEval = evaluate(pos);
+        eval = ss->staticEval =
+        (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
+
         TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);
     }
 
@@ -555,6 +554,7 @@ namespace {
         &&  ss->staticEval != VALUE_NONE
         && (ss-1)->staticEval != VALUE_NONE
         && (move = (ss-1)->currentMove) != MOVE_NULL
+        &&  move != MOVE_NONE
         &&  type_of(move) == NORMAL)
     {
         Square to = to_sq(move);
@@ -566,7 +566,6 @@ namespace {
         &&  depth < 4 * ONE_PLY
         &&  eval + razor_margin(depth) <= alpha
         &&  ttMove == MOVE_NONE
-        &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         && !pos.pawn_on_7th(pos.side_to_move()))
     {
         if (   depth <= ONE_PLY
@@ -594,7 +593,6 @@ namespace {
         && !ss->skipNullMove
         &&  depth >= 2 * ONE_PLY
         &&  eval >= beta
-        &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         &&  pos.non_pawn_material(pos.side_to_move()))
     {
         ss->currentMove = MOVE_NULL;
@@ -604,7 +602,8 @@ namespace {
         // Null move dynamic reduction based on depth and value
         Depth R =  3 * ONE_PLY
                  + depth / 4
-                 + int(eval - beta) / PawnValueMg * ONE_PLY;
+                 + (abs(beta) < VALUE_KNOWN_WIN ? int(eval - beta) / PawnValueMg * ONE_PLY
+                                                : DEPTH_ZERO);
 
         pos.do_null_move(st);
         (ss+1)->skipNullMove = true;
@@ -619,7 +618,7 @@ namespace {
             if (nullValue >= VALUE_MATE_IN_MAX_PLY)
                 nullValue = beta;
 
-            if (depth < 12 * ONE_PLY)
+            if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN)
                 return nullValue;
 
             // Do verification search at high depths
@@ -699,7 +698,10 @@ moves_loop: // When in check and at SpNode search starts from here
     singularExtensionNode =   !RootNode
                            && !SpNode
                            &&  depth >= 8 * ONE_PLY
+                           &&  abs(beta) < VALUE_KNOWN_WIN
                            &&  ttMove != MOVE_NONE
+                       /*  &&  ttValue != VALUE_NONE Already implicit in the next condition */
+                           &&  abs(ttValue) < VALUE_KNOWN_WIN
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
@@ -764,11 +766,8 @@ moves_loop: // When in check and at SpNode search starts from here
       if (    singularExtensionNode
           &&  move == ttMove
           && !ext
-          &&  pos.legal(move, ci.pinned)
-          &&  abs(ttValue) < VALUE_KNOWN_WIN)
+          &&  pos.legal(move, ci.pinned))
       {
-          assert(ttValue != VALUE_NONE);
-
           Value rBeta = ttValue - int(depth);
           ss->excludedMove = move;
           ss->skipNullMove = true;
@@ -870,8 +869,9 @@ moves_loop: // When in check and at SpNode search starts from here
 
           // Decrease reduction for moves that escape a capture
           if (   ss->reduction
+              && type_of(move) == NORMAL
               && type_of(pos.piece_on(to_sq(move))) != PAWN
-              && pos.see_sign(make_move(to_sq(move), from_sq(move))) < 0)
+              && pos.see(make_move(to_sq(move), from_sq(move))) < 0)
               ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
 
           Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
@@ -1109,7 +1109,8 @@ moves_loop: // When in check and at SpNode search starts from here
                     bestValue = ttValue;
         }
         else
-            ss->staticEval = bestValue = evaluate(pos);
+            ss->staticEval = bestValue =
+            (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
 
         // Stand pat. Return immediately if static value is at least beta
         if (bestValue >= beta)