More extensions if SE search is very low.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1d84102303989cce47a9e3ea2615ec623d8fd159..5542fc87366a0923a5f2122ad91144c0def70a1f 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1130,6 +1130,8 @@ moves_loop: // When in check, search starts from here
           {
               extension = 1;
               singularQuietLMR = !ttCapture;
+              if (!PvNode && value < singularBeta - 140)
+                  extension = 2;
           }
 
           // Multi-cut pruning
@@ -1185,7 +1187,8 @@ moves_loop: // When in check, search starts from here
               || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
               || cutNode
               || (!PvNode && !formerPv && captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 3678)
-              || thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
+              || thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024)
+          && (!PvNode || ss->ply > 1 || thisThread->id() % 4 != 3))
       {
           Depth r = reduction(improving, depth, moveCount);