From a39e0f7438aee78766a5875f2d29f7c54aff68dc Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 16 Oct 2018 01:04:25 +0200
Subject: [PATCH] bug #1612: fix regression in "outer-vectorization" of partial
 reductions for PacketSize==1 (aka complex<double>)

---
 Eigen/src/Core/PartialReduxEvaluator.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Eigen/src/Core/PartialReduxEvaluator.h b/Eigen/src/Core/PartialReduxEvaluator.h
index e524f32a6..0be694259 100644
--- a/Eigen/src/Core/PartialReduxEvaluator.h
+++ b/Eigen/src/Core/PartialReduxEvaluator.h
@@ -205,6 +205,13 @@ struct evaluator<PartialReduxExpr<ArgType, MemberOp, Direction> >
                     Direction==Vertical ? idx : 0,
                     Direction==Vertical ? m_arg.rows() : Index(PacketSize),
                     Direction==Vertical ? Index(PacketSize) : m_arg.cols());
+
+    // FIXME
+    // See bug 1612, currently if PacketSize==1 (i.e. complex<double> with 128bits registers) then the storage-order of panel get reversed
+    // and methods like packetByOuterInner do not make sense anymore in this context.
+    // So let's just by pass "vectorization" in this case:
+    if(PacketSize==1)
+      return internal::pset1<PacketType>(coeff(idx));
     
     typedef typename internal::redux_evaluator<PanelType> PanelEvaluator;
     PanelEvaluator panel_eval(panel);