X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=cd815c2af266e679294ff81ba0f5806f7b548d4a;hp=0068cbcac2e609079da443003ca267a87745c933;hb=5413fda7397f8ffe32e41b9c7f13297c39929f5c;hpb=a1f39c1ef906bb2e6bb75485f5469831cee32522

diff --git a/src/search.cpp b/src/search.cpp
index 0068cbca..cd815c2a 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -45,7 +45,6 @@ namespace Search {
   Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
-  Value Contempt[2]; // [bestValue > VALUE_DRAW]
 }
 
 using std::string;
@@ -186,9 +185,9 @@ void Search::think() {
   RootColor = RootPos.side_to_move();
   TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
 
-  DrawValue[0] = DrawValue[1] = VALUE_DRAW;
-  Contempt[0] =  Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
-  Contempt[1] = (Options["Contempt Factor"] + 12) * PawnValueEg / 100;
+  int cf = Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
+  DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
+  DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
 
   if (RootMoves.empty())
   {
@@ -340,9 +339,6 @@ namespace {
             {
                 bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
 
-                DrawValue[ RootColor] = VALUE_DRAW - Contempt[bestValue > VALUE_DRAW];
-                DrawValue[~RootColor] = VALUE_DRAW + Contempt[bestValue > VALUE_DRAW];
-
                 // Bring the best move to the front. It is critical that sorting
                 // is done with a stable algorithm because all the values but the
                 // first and eventually the new best one are set to -VALUE_INFINITE
@@ -936,12 +932,11 @@ moves_loop: // When in check and at SpNode search starts from here
           alpha = splitPoint->alpha;
       }
 
-      // Finished searching the move. If Signals.stop is true, the search
-      // was aborted because the user interrupted the search or because we
-      // ran out of time. In this case, the return value of the search cannot
-      // be trusted, and we don't update the best move and/or PV.
+      // Finished searching the move. If a stop or a cutoff occurred, the return
+      // value of the search cannot be trusted, and we return immediately without
+      // updating best move, PV and TT.
       if (Signals.stop || thisThread->cutoff_occurred())
-          return value; // To avoid returning VALUE_INFINITE
+          return VALUE_ZERO;
 
       if (RootNode)
       {
@@ -994,10 +989,14 @@ moves_loop: // When in check and at SpNode search starts from here
           &&  Threads.available_slave(thisThread)
           &&  thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
       {
-          assert(bestValue < beta);
+          assert(bestValue > -VALUE_INFINITE && bestValue < beta);
 
           thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
                                        depth, moveCount, &mp, NT, cutNode);
+
+          if (Signals.stop || thisThread->cutoff_occurred())
+              return VALUE_ZERO;
+
           if (bestValue >= beta)
               break;
       }
@@ -1006,21 +1005,22 @@ moves_loop: // When in check and at SpNode search starts from here
     if (SpNode)
         return bestValue;
 
+    // Following condition would detect a stop or a cutoff set only after move
+    // loop has been completed. But in this case bestValue is valid because we
+    // have fully searched our subtree, and we can anyhow save the result in TT.
+    /*
+       if (Signals.stop || thisThread->cutoff_occurred())
+        return VALUE_DRAW;
+    */
+
     // Step 20. Check for mate and stalemate
     // All legal moves have been searched and if there are no legal moves, it
-    // must be mate or stalemate. Note that we can have a false positive in
-    // case of Signals.stop or thread.cutoff_occurred() are set, but this is
-    // harmless because return value is discarded anyhow in the parent nodes.
-    // If we are in a singular extension search then return a fail low score.
-    // A split node has at least one move - the one tried before to be split.
+    // must be mate or stalemate. If we are in a singular extension search then
+    // return a fail low score.
     if (!moveCount)
         return  excludedMove ? alpha
               : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
 
-    // If we have pruned all the moves without searching return a fail-low score
-    if (bestValue == -VALUE_INFINITE)
-        bestValue = alpha;
-
     TT.store(posKey, value_to_tt(bestValue, ss->ply),
              bestValue >= beta  ? BOUND_LOWER :
              PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,