From 7f62ac8fd541016021231225958d2c40512ada14 Mon Sep 17 00:00:00 2001
From: Michael Chaly <Vizvezdenec@gmail.com>
Date: Tue, 23 Jul 2024 16:36:49 +0300
Subject: [PATCH] Introduce pre-qsearch ttmove extensions at pv nodes

The idea is that we are about to dive into qsearch (next search depth is <= 0)
but since we have the move in transposition table we should extend that move
and evaluate it with more precise search - because branch seems important.
---
 src/search.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/search.cpp b/src/search.cpp
index 3fbbbc54..b689f582 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1113,6 +1113,10 @@ Value Search::Worker::search(
             (ss + 1)->pv    = pv;
             (ss + 1)->pv[0] = Move::none();
 
+            // Extend move from transposition table if we are about to dive into qsearch.
+            if (move == ttData.move && ss->ply <= thisThread->rootDepth * 2)
+                newDepth = std::max(newDepth, 1);
+
             value = -search<PV>(pos, ss + 1, -beta, -alpha, newDepth, false);
         }