From e404a7d97c94890dda18ca3a16cfd15b5a7ef235 Mon Sep 17 00:00:00 2001
From: Michael Chaly <Vizvezdenec@gmail.com>
Date: Mon, 6 Sep 2021 00:17:46 +0300
Subject: [PATCH] Extend captures and promotions

This patch introduces extension for captures and promotions. Every capture or
promotion that is not the first move in the list gets extended at PvNodes and
cutNodes. Special thanks to @locutus2 - all my previous attepmts that failed
on this idea were done only for PvNodes - idea to include also cutNodes was
based on his latest passed patch.

STC
https://tests.stockfishchess.org/tests/view/6134abf325b9b35584838574
LLR: 2.95 (-2.94,2.94) <-0.50,2.50>
Total: 188920 W: 47754 L: 47304 D: 93862
Ptnml(0-2): 595, 21754, 49344, 22140, 627

LTC
https://tests.stockfishchess.org/tests/view/613521de25b9b355848385d7
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 8768 W: 2283 L: 2098 D: 4387
Ptnml(0-2): 7, 866, 2452, 1053, 6

closes https://github.com/official-stockfish/Stockfish/pull/3692

bench: 5564555
---
 src/search.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/search.cpp b/src/search.cpp
index 5aa50644..0d7575aa 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1094,6 +1094,14 @@ moves_loop: // When in check, search starts here
                   return beta;
           }
       }
+
+      // Capture extensions for PvNodes and cutNodes
+      else if (   (PvNode || cutNode) 
+               && captureOrPromotion 
+               && moveCount != 1)
+          extension = 1;
+
+      // Check extensions
       else if (   givesCheck
                && depth > 6
                && abs(ss->staticEval) > Value(100))
-- 
2.39.2