Fix a segfault.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 6a63fcaa338910a221d2770374faea8ead35f183..5b6a048500b0842c1b59a97f7913532139ae54e0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -303,6 +303,7 @@ void MainThread::search() {
 void Thread::search() {
 
   Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2)
+  Move  pv[MAX_PLY+1];
   Value bestValue, alpha, beta, delta;
   Move  lastBestMove = MOVE_NONE;
   Depth lastBestMoveDepth = DEPTH_ZERO;
@@ -314,6 +315,7 @@ void Thread::search() {
   std::memset(ss-4, 0, 7 * sizeof(Stack));
   for (int i = 4; i > 0; i--)
      (ss-i)->continuationHistory = &this->continuationHistory[NO_PIECE][0]; // Use as sentinel
+  ss->pv = pv;
 
   bestValue = delta = alpha = -VALUE_INFINITE;
   beta = VALUE_INFINITE;
@@ -448,7 +450,7 @@ void Thread::search() {
               {
                   beta = std::min(bestValue + delta, VALUE_INFINITE);
                   if (mainThread)
-                         ++failedHighCnt;
+                      ++failedHighCnt;
               }
               else
                   break;
@@ -756,15 +758,16 @@ namespace {
     }
 
     // Step 7. Razoring (~2 Elo)
-    if (   depth < 2 * ONE_PLY
-        && eval <= alpha - RazorMargin)
+    if (   !rootNode // The required rootNode PV handling is not available in qsearch
+        &&  depth < 2 * ONE_PLY
+        &&  eval <= alpha - RazorMargin)
         return qsearch<NT>(pos, ss, alpha, beta);
 
     improving =   ss->staticEval >= (ss-2)->staticEval
                || (ss-2)->staticEval == VALUE_NONE;
 
     // Step 8. Futility pruning: child node (~30 Elo)
-    if (   !rootNode
+    if (   !PvNode
         &&  depth < 7 * ONE_PLY
         &&  eval - futility_margin(depth, improving) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
@@ -826,8 +829,8 @@ namespace {
         &&  depth >= 5 * ONE_PLY
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY)
     {
-        Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
-        MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory);
+        Value raisedBeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
+        MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory);
         int probCutCount = 0;
 
         while (  (move = mp.next_move()) != MOVE_NONE
@@ -844,15 +847,15 @@ namespace {
                 pos.do_move(move, st);
 
                 // Perform a preliminary qsearch to verify that the move holds
-                value = -qsearch<NonPV>(pos, ss+1, -rbeta, -rbeta+1);
+                value = -qsearch<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1);
 
                 // If the qsearch held perform the regular search
-                if (value >= rbeta)
-                    value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode);
+                if (value >= raisedBeta)
+                    value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4 * ONE_PLY, !cutNode);
 
                 pos.undo_move(move);
 
-                if (value >= rbeta)
+                if (value >= raisedBeta)
                     return value;
             }
     }
@@ -928,18 +931,18 @@ moves_loop: // When in check, search starts from here
       if (    depth >= 8 * ONE_PLY
           &&  move == ttMove
           && !rootNode
-          && !excludedMove // Recursive singular search is not allowed
+          && !excludedMove // Avoid recursive singular search
           &&  ttValue != VALUE_NONE
           && (tte->bound() & BOUND_LOWER)
           &&  tte->depth() >= depth - 3 * ONE_PLY
           &&  pos.legal(move))
       {
-          Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
+          Value reducedBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
           ss->excludedMove = move;
-          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+          value = search<NonPV>(pos, ss, reducedBeta - 1, reducedBeta, depth / 2, cutNode);
           ss->excludedMove = MOVE_NONE;
 
-          if (value < rBeta)
+          if (value < reducedBeta)
               extension = ONE_PLY;
       }
       else if (    givesCheck // Check extension (~2 Elo)
@@ -960,7 +963,7 @@ moves_loop: // When in check, search starts from here
       {
           if (   !captureOrPromotion
               && !givesCheck
-              && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000)))
+              && !pos.advanced_pawn_push(move))
           {
               // Move count based pruning (~30 Elo)
               if (moveCountPruning)
@@ -973,7 +976,7 @@ moves_loop: // When in check, search starts from here
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
-              if (   lmrDepth < 3 + ((ss-1)->statScore > 0)
+              if (   lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
                   && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;
@@ -1185,15 +1188,12 @@ moves_loop: // When in check, search starts from here
 
         update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
 
-        // Extra penalty for a quiet TT move in previous ply when it gets refuted
-        if ((ss-1)->moveCount == 1 && !pos.captured_piece())
-            update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+        // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted
+        if (   (ss-1)->moveCount == 1
+            || ((ss-1)->currentMove == (ss-1)->killers[0] && (ss-1)->killers[0]))
+            if (!pos.captured_piece())
+                update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
 
-        // Extra penalty for killer move in previous ply when it gets refuted
-        else if (  (ss-1)->killers[0]
-                && (ss-1)->currentMove == (ss-1)->killers[0]
-                && !pos.captured_piece())
-            update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth));
     }
     // Bonus for prior countermove that caused the fail low
     else if (   (depth >= 3 * ONE_PLY || PvNode)