From 53125902e461ae129b408a81ada07aaf44810c6c Mon Sep 17 00:00:00 2001
From: Moez Jellouli <37274752+MJZ1977@users.noreply.github.com>
Date: Sun, 24 Nov 2019 21:57:09 +0100
Subject: [PATCH] Extend last non-pawn captures

Extend last non-pawn captures at principal variation nodes because
they are in general decisive moves with clear endgame result.

STC
http://tests.stockfishchess.org/tests/view/5ddafc86e75c0005326d2140
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 9892 W: 2238 L: 2099 D: 5555

LTC
http://tests.stockfishchess.org/tests/view/5ddb0401e75c0005326d2150
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 30369 W: 5013 L: 4756 D: 20600

Closes https://github.com/official-stockfish/Stockfish/pull/2425

Bench: 5059526
---
 src/search.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/search.cpp b/src/search.cpp
index d3f38aae..e976274f 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1049,6 +1049,12 @@ moves_loop: // When in check, search starts from here
                && pos.pawn_passed(us, to_sq(move)))
           extension = 1;
 
+      // Last captures extension
+      else if (   PvNode
+               && PieceValue[EG][pos.captured_piece()] > PawnValueEg
+               && pos.non_pawn_material() <= 2 * RookValueMg)
+          extension = 1;
+
       // Castling extension
       if (type_of(move) == CASTLING)
           extension = 1;
-- 
2.39.2