From aeffdf909eb79dace9f12d0c38583f0dad106f54 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Wed, 16 Jan 2019 15:24:59 +0100
Subject: [PATCH] bug #1617: add unit tests for empty triangular solve.

---
 test/product_trsolve.cpp | 13 +++++++++++++
 test/sparse_solvers.cpp  | 13 +++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/test/product_trsolve.cpp b/test/product_trsolve.cpp
index 0c22cccf6..c927cb635 100644
--- a/test/product_trsolve.cpp
+++ b/test/product_trsolve.cpp
@@ -71,6 +71,19 @@ template<typename Scalar,int Size, int Cols> void trsolve(int size=Size,int cols
   int c = internal::random<int>(0,cols-1);
   VERIFY_TRSM(rmLhs.template triangularView<Lower>(), rmRhs.col(c));
   VERIFY_TRSM(cmLhs.template triangularView<Lower>(), rmRhs.col(c));
+
+  if(Size==Dynamic)
+  {
+    cmLhs.resize(0,0);
+    cmRhs.resize(0,cmRhs.cols());
+    Matrix<Scalar,Size,Cols,colmajor> res = cmLhs.template triangularView<Lower>().solve(cmRhs);
+    VERIFY_IS_EQUAL(res.rows(),0);
+    VERIFY_IS_EQUAL(res.cols(),cmRhs.cols());
+    res = cmRhs;
+    cmLhs.template triangularView<Lower>().solveInPlace(res);
+    VERIFY_IS_EQUAL(res.rows(),0);
+    VERIFY_IS_EQUAL(res.cols(),cmRhs.cols());
+  }
 }
 
 EIGEN_DECLARE_TEST(product_trsolve)
diff --git a/test/sparse_solvers.cpp b/test/sparse_solvers.cpp
index aaf3d39c9..3b7cd7788 100644
--- a/test/sparse_solvers.cpp
+++ b/test/sparse_solvers.cpp
@@ -98,6 +98,19 @@ template<typename Scalar> void sparse_solvers(int rows, int cols)
     initSparse<Scalar>(density, refMat2, m2, ForceNonZeroDiag|MakeLowerTriangular, &zeroCoords, &nonzeroCoords);
     VERIFY_IS_APPROX(refMat2.template triangularView<Lower>().solve(vec2),
                      m2.template triangularView<Lower>().solve(vec3));
+
+    // test empty triangular matrix
+    {
+      m2.resize(0,0);
+      refMatB.resize(0,refMatB.cols());
+      DenseMatrix res = m2.template triangularView<Lower>().solve(refMatB);
+      VERIFY_IS_EQUAL(res.rows(),0);
+      VERIFY_IS_EQUAL(res.cols(),refMatB.cols());
+      res = refMatB;
+      m2.template triangularView<Lower>().solveInPlace(res);
+      VERIFY_IS_EQUAL(res.rows(),0);
+      VERIFY_IS_EQUAL(res.cols(),refMatB.cols());
+    }
   }
 }