From a255ad59e3ab9bc0e806954e1ee0205da13b4030 Mon Sep 17 00:00:00 2001
From: mstembera <5421953+mstembera@users.noreply.github.com>
Date: Thu, 16 Jul 2026 08:18:06 +0200
Subject: [PATCH] Optimize evasions in Position::pseudo_legal()

STC: https://tests.stockfishchess.org/tests/view/6a4be17d5529b8472df7fa60
LLR: 3.68 (-2.94,2.94) <0.00,2.00>
Total: 405888 W: 105701 L: 104837 D: 195350
Ptnml(0-2): 872, 42472, 115373, 43374, 853

closes https://github.com/official-stockfish/Stockfish/pull/6968

No functional change
---
 src/position.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/position.cpp b/src/position.cpp
index 4279f89d4..42bb871a4 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -745,8 +745,16 @@ bool Position::pseudo_legal(const Move m) const {
     else if (!(attacks_bb(type_of(pc), from, pieces()) & to))
         return false;
 
-    if (checkers())
-        return MoveList<EVASIONS>(*this).contains(m);
+    if (checkers() && type_of(pc) != KING)
+    {
+        // In double check, only a king move can evade
+        if (more_than_one(checkers()))
+            return false;
+
+        // The move must block the check or capture the checker
+        if (!(between_bb(square<KING>(us), lsb(checkers())) & to))
+            return false;
+    }
 
     return true;
 }