From 8a06c699d0f8d47f4fc4f259a21574b4719792b2 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 29 Jan 2019 10:27:13 +0100
Subject: bug #1669: fix PartialPivLU/inverse with zero-sized matrices.

---
 Eigen/src/LU/PartialPivLU.h |  5 ++++-
 test/inverse.cpp            | 17 +++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/LU/PartialPivLU.h b/Eigen/src/LU/PartialPivLU.h
index 8726bf895..b414b5c46 100644
--- a/Eigen/src/LU/PartialPivLU.h
+++ b/Eigen/src/LU/PartialPivLU.h
@@ -511,7 +511,10 @@ void PartialPivLU<MatrixType>::compute()
   // the row permutation is stored as int indices, so just to be sure:
   eigen_assert(m_lu.rows()<NumTraits<int>::highest());
 
-  m_l1_norm = m_lu.cwiseAbs().colwise().sum().maxCoeff();
+  if(m_lu.cols()>0)
+    m_l1_norm = m_lu.cwiseAbs().colwise().sum().maxCoeff();
+  else
+    m_l1_norm = RealScalar(0);
 
   eigen_assert(m_lu.rows() == m_lu.cols() && "PartialPivLU is only for square (and moreover invertible) matrices");
   const Index size = m_lu.rows();
diff --git a/test/inverse.cpp b/test/inverse.cpp
index 8754cb7e5..99f9e0c9b 100644
--- a/test/inverse.cpp
+++ b/test/inverse.cpp
@@ -105,6 +105,22 @@ template<typename MatrixType> void inverse(const MatrixType& m)
   }
 }
 
+template<typename Scalar>
+void inverse_zerosized()
+{
+  Matrix<Scalar,Dynamic,Dynamic> A(0,0);
+  {
+    Matrix<Scalar,0,1> b, x;
+    x = A.inverse() * b;
+  }
+  {
+    Matrix<Scalar,Dynamic,Dynamic> b(0,1), x;
+    x = A.inverse() * b;
+    VERIFY_IS_EQUAL(x.rows(), 0);
+    VERIFY_IS_EQUAL(x.cols(), 1);
+  }
+}
+
 EIGEN_DECLARE_TEST(inverse)
 {
   int s = 0;
@@ -118,6 +134,7 @@ EIGEN_DECLARE_TEST(inverse)
     s = internal::random<int>(50,320); 
     CALL_SUBTEST_5( inverse(MatrixXf(s,s)) );
     TEST_SET_BUT_UNUSED_VARIABLE(s)
+    CALL_SUBTEST_5( inverse_zerosized<float>() );
     
     s = internal::random<int>(25,100);
     CALL_SUBTEST_6( inverse(MatrixXcd(s,s)) );
-- 
cgit v1.2.3