From 2067b54b135adede6fb9124f3d457cac53538913 Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Mon, 13 Mar 2023 18:25:22 +0000
Subject: [PATCH] Fix bug in minmax_coeff_visitor for matrix of all NaNs.

---
 Eigen/src/Core/Visitor.h | 11 +++++++++--
 test/visitor.cpp         | 21 ++++++++++++++++++++-
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/Core/Visitor.h b/Eigen/src/Core/Visitor.h
index 4e9a85e80..7b29dae22 100644
--- a/Eigen/src/Core/Visitor.h
+++ b/Eigen/src/Core/Visitor.h
@@ -453,6 +453,7 @@ struct minmax_compare<Scalar, NaNPropagation, false> {
   static EIGEN_DEVICE_FUNC inline Scalar predux(const Packet& p) { return predux_max<NaNPropagation>(p); }
 };
 
+// Default imlementatio
 template <typename Derived, bool is_min, int NaNPropagation>
 struct minmax_coeff_visitor : coeff_visitor<Derived> {
   using Scalar = typename Derived::Scalar;
@@ -489,8 +490,8 @@ struct minmax_coeff_visitor : coeff_visitor<Derived> {
   }
 };
 
-// Suppress NaN. The only case in which we return NaN is if the matrix is all NaN, in which case,
-// the row=0, col=0 is returned for the location.
+// Suppress NaN. The only case in which we return NaN is if the matrix is all NaN,
+// in which case, row=0, col=0 is returned for the location.
 template <typename Derived, bool is_min>
 struct minmax_coeff_visitor<Derived, is_min, PropagateNumbers> : coeff_visitor<Derived> {
   typedef typename Derived::Scalar Scalar;
@@ -520,6 +521,12 @@ struct minmax_coeff_visitor<Derived, is_min, PropagateNumbers> : coeff_visitor<D
   EIGEN_DEVICE_FUNC inline void initpacket(const Packet& p, Index i, Index j) {
     const Index PacketSize = packet_traits<Scalar>::size;
     Scalar value = Comparator::predux(p);
+    if ((numext::isnan)(value)) {
+      this->res = value;
+      this->row = 0;
+      this->col = 0;
+      return;
+    }
     const Packet range = preverse(plset<Packet>(Scalar(1)));
     /* mask will be zero for NaNs, so they will be ignored. */
     Packet mask = pcmp_eq(pset1<Packet>(value), p);
diff --git a/test/visitor.cpp b/test/visitor.cpp
index 9586539a2..174a1bb1d 100644
--- a/test/visitor.cpp
+++ b/test/visitor.cpp
@@ -92,8 +92,27 @@ template<typename MatrixType> void matrixVisitor(const MatrixType& p)
     VERIFY(maxrow != eigen_maxrow || maxcol != eigen_maxcol);
     VERIFY((numext::isnan)(eigen_minc));
     VERIFY((numext::isnan)(eigen_maxc));
-  }
 
+    // Test matrix of all NaNs.
+    m.fill(NumTraits<Scalar>::quiet_NaN());
+    eigen_minc = m.template minCoeff<PropagateNumbers>(&eigen_minrow, &eigen_mincol);
+    eigen_maxc = m.template maxCoeff<PropagateNumbers>(&eigen_maxrow, &eigen_maxcol);
+    VERIFY(eigen_minrow == 0);
+    VERIFY(eigen_maxrow == 0);
+    VERIFY(eigen_mincol == 0);
+    VERIFY(eigen_maxcol == 0);
+    VERIFY((numext::isnan)(eigen_minc));
+    VERIFY((numext::isnan)(eigen_maxc));
+
+    eigen_minc = m.template minCoeff<PropagateNaN>(&eigen_minrow, &eigen_mincol);
+    eigen_maxc = m.template maxCoeff<PropagateNaN>(&eigen_maxrow, &eigen_maxcol);
+    VERIFY(eigen_minrow == 0);
+    VERIFY(eigen_maxrow == 0);
+    VERIFY(eigen_mincol == 0);
+    VERIFY(eigen_maxcol == 0);
+    VERIFY((numext::isnan)(eigen_minc));
+    VERIFY((numext::isnan)(eigen_maxc));
+  }
 }
 
 template<typename VectorType> void vectorVisitor(const VectorType& w)