From 0ac2a2df9ffa81f2e5575dfdb3e56ad8a5f50893 Mon Sep 17 00:00:00 2001
From: Chip Kerchner <ckerchner@tenstorrent.com>
Date: Sun, 8 Feb 2026 13:19:45 -0500
Subject: [PATCH] Prevent predux_half for DoublePacket from accidentally
 catching complex Packets of size >= 16

libeigen/eigen!2125
---
 Eigen/src/Core/products/GeneralBlockPanelKernel.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/products/GeneralBlockPanelKernel.h b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
index 7238fcd23..c2a4eab29 100644
--- a/Eigen/src/Core/products/GeneralBlockPanelKernel.h
+++ b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
@@ -650,7 +650,9 @@ const DoublePacket<Packet>& predux_half(const DoublePacket<Packet>& a,
 
 template <typename Packet>
 DoublePacket<typename unpacket_traits<Packet>::half> predux_half(
-    const DoublePacket<Packet>& a, std::enable_if_t<unpacket_traits<Packet>::size == 16>* = 0) {
+    const DoublePacket<Packet>& a,
+    std::enable_if_t<unpacket_traits<Packet>::size >= 16 &&
+                     !NumTraits<typename unpacket_traits<Packet>::type>::IsComplex>* = 0) {
   // yes, that's pretty hackish :(
   DoublePacket<typename unpacket_traits<Packet>::half> res;
   typedef std::complex<typename unpacket_traits<Packet>::type> Cplx;