Less pruning in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index a2342a3cf4f90d50eeccce10a8d25a6afceef3e2..0d823c8e02425d1cf617d7a7e1939490d4c4b600 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -944,7 +944,7 @@ namespace {
             }
          ss->ttPv = ttPv;
     }
-    
+
     // Step 11. If the position is not in TT, decrease depth by 2
     if (   PvNode
         && depth >= 6
@@ -1160,7 +1160,6 @@ moves_loop: // When in check, search starts from here
       // re-searched at full depth.
       if (    depth >= 3
           &&  moveCount > 1 + 2 * rootNode + 2 * (PvNode && abs(bestValue) < 2)
-          && (!rootNode || thisThread->best_move_count(move) == 0)
           && (  !captureOrPromotion
               || moveCountPruning
               || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
@@ -1565,7 +1564,9 @@ moves_loop: // When in check, search starts from here
       }
 
       // Do not search moves with negative SEE values
-      if (!ss->inCheck && !pos.see_ge(move))
+      if (   !ss->inCheck
+          && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))
+          && !pos.see_ge(move))
           continue;
 
       // Speculative prefetch as early as possible
@@ -1585,7 +1586,7 @@ moves_loop: // When in check, search starts from here
                                                                 [to_sq(move)];
 
       if (  !captureOrPromotion
-          && moveCount >= abs(depth) + 1
+          && moveCount
           && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
           && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold)
           continue;
@@ -1861,12 +1862,15 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
   {
       bool updated = rootMoves[i].score != -VALUE_INFINITE;
 
-      if (depth == 1 && !updated)
+      if (depth == 1 && !updated && i > 0)
           continue;
 
-      Depth d = updated ? depth : depth - 1;
+      Depth d = updated ? depth : std::max(1, depth - 1);
       Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
 
+      if (v == -VALUE_INFINITE)
+          v = VALUE_ZERO;
+
       bool tb = TB::RootInTB && abs(v) < VALUE_MATE_IN_MAX_PLY;
       v = tb ? rootMoves[i].tbScore : v;
 
@@ -1964,7 +1968,7 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
     if (RootInTB)
     {
         // Sort moves according to TB rank
-        std::sort(rootMoves.begin(), rootMoves.end(),
+        std::stable_sort(rootMoves.begin(), rootMoves.end(),
                   [](const RootMove &a, const RootMove &b) { return a.tbRank > b.tbRank; } );
 
         // Probe during search only if DTZ is not available and we are winning