From c31fc8d163ed2c5ff5697206f8a5eef65efa0044 Mon Sep 17 00:00:00 2001
From: Stefan Geschwentner <stgeschwentner@gmail.com>
Date: Mon, 6 Sep 2021 11:22:58 +0200
Subject: [PATCH] Improve history updates

If a search failed low at an expected PV or CUT node do greater history updates.

STC:
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 95112 W: 24293 L: 23982 D: 46837
Ptnml(0-2): 285, 10893, 24906, 11170, 302
https://tests.stockfishchess.org/tests/view/6132aa1a2ffb3c36aceb926f

LTC:
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 116352 W: 29450 L: 28975 D: 57927
Ptnml(0-2): 93, 12263, 32984, 12748, 88
https://tests.stockfishchess.org/tests/view/613394d12ffb3c36aceb92f4

closes https://github.com/official-stockfish/Stockfish/pull/3693

Bench: 6130736
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 0d7575aa..6affa510 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1325,7 +1325,7 @@ moves_loop: // When in check, search starts here
     // Bonus for prior countermove that caused the fail low
     else if (   (depth >= 3 || PvNode)
              && !priorCapture)
-        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
+        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth + (PvNode || cutNode)));
 
     if (PvNode)
         bestValue = std::min(bestValue, maxValue);