From b36d39de3d61b8f31c11d85233631aafaf760ee1 Mon Sep 17 00:00:00 2001
From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Sun, 9 Apr 2023 09:18:29 +0200
Subject: [PATCH] Fix rootComplexity calculation

The calculation of rootComplexity can't call eval when in check.
Doing so triggers an assert if compiled in debug mode when
the rootpos is evaluated using classical eval.

Fixes https://github.com/official-stockfish/Stockfish/issues/4512

Passed STC:
https://tests.stockfishchess.org/tests/view/6432697431feee5c6d306876
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 41096 W: 11017 L: 10815 D: 19264
Ptnml(0-2): 113, 4172, 11780, 4366, 117

Running LTC:
https://tests.stockfishchess.org/tests/view/6432974d31feee5c6d306fc0
LLR: 1.76 (-2.94,2.94) <-1.75,0.25>
Total: 73200 W: 19792 L: 19728 D: 33680
Ptnml(0-2): 24, 6659, 23182, 6699, 36

closes https://github.com/official-stockfish/Stockfish/pull/4515

No functional change
---
 src/evaluate.cpp |  2 ++
 src/search.cpp   | 10 ++++++----
 src/thread.cpp   |  1 +
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 703cf869..2d0df89c 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1048,6 +1048,8 @@ make_v:
 
 Value Eval::evaluate(const Position& pos, int* complexity) {
 
+  assert(!pos.checkers());
+
   Value v;
   Value psq = pos.psq_eg_stm();
 
diff --git a/src/search.cpp b/src/search.cpp
index fba9685b..5d54a15d 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -295,10 +295,12 @@ void Thread::search() {
   if (mainThread)
   {
 
-      int rootComplexity;
-      Eval::evaluate(rootPos, &rootComplexity);
-
-      mainThread->complexity = std::min(1.03 + (rootComplexity - 241) / 1552.0, 1.45);
+      if (!rootPos.checkers())
+      {
+          int rootComplexity;
+          Eval::evaluate(rootPos, &rootComplexity);
+          mainThread->complexity = std::min(1.03 + (rootComplexity - 241) / 1552.0, 1.45);
+      }
 
       if (mainThread->bestPreviousScore == VALUE_INFINITE)
           for (int i = 0; i < 4; ++i)
diff --git a/src/thread.cpp b/src/thread.cpp
index c680393e..202768c8 100644
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -160,6 +160,7 @@ void ThreadPool::clear() {
   main()->bestPreviousScore = VALUE_INFINITE;
   main()->bestPreviousAverageScore = VALUE_INFINITE;
   main()->previousTimeReduction = 1.0;
+  main()->complexity = 1.0;
 }
 
 
-- 
2.39.2