Correctly track down pv even in fail-high case

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 8d325a8e71d7b7faca4c8cdb0fec89a6840571ea..5445256f3a85d0a0537f985c987674729a995c86 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -757,7 +757,7 @@ namespace {
         && (ss-1)->currentMove != MOVE_NULL
         && (ss-1)->statScore < 23200
         &&  eval >= beta
-        &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+        &&  pureStaticEval >= beta - 36 * depth / ONE_PLY + 225
         && !excludedMove
         &&  pos.non_pawn_material(us)
         && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -863,7 +863,7 @@ moves_loop: // When in check, search starts from here
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
 
     skipQuiets = false;
-    ttCapture = false;
+    ttCapture = ttMove && pos.capture_or_promotion(ttMove);
     pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;
 
     // Step 12. Loop through all pseudo-legal moves until no moves remain
@@ -905,7 +905,7 @@ moves_loop: // When in check, search starts from here
       // Singular extension search (~60 Elo). If all moves but one fail low on a
       // search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
       // then that move is singular and should be extended. To verify this we do
-      // a reduced search on on all the other moves but the ttMove and if the
+      // a reduced search on all the other moves but the ttMove and if the
       // result is lower than ttValue minus a margin then we will extend the ttMove.
       if (    depth >= 8 * ONE_PLY
           &&  move == ttMove
@@ -982,9 +982,6 @@ moves_loop: // When in check, search starts from here
           continue;
       }
 
-      if (move == ttMove && captureOrPromotion)
-          ttCapture = true;
-
       // Update the current move (this must be done after singular extension search)
       ss->currentMove = move;
       ss->continuationHistory = &thisThread->continuationHistory[movedPiece][to_sq(move)];
@@ -1128,6 +1125,8 @@ moves_loop: // When in check, search starts from here
                   break;
               }
           }
+          else if (PvNode && !rootNode && value == alpha)
+              update_pv(ss->pv, move, (ss+1)->pv);
       }
 
       if (move != bestMove)