From eedb87f4ba7fa835808168952f70acac6e458452 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Mon, 14 Nov 2016 14:05:53 +0100
Subject: [PATCH] Fix regression in SparseMatrix::ReverseInnerIterator

---
 Eigen/src/SparseCore/SparseCompressedBase.h | 11 ++++----
 test/sparse_basic.cpp                       | 30 +++++++++++++++++++++
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/Eigen/src/SparseCore/SparseCompressedBase.h b/Eigen/src/SparseCore/SparseCompressedBase.h
index 55ad91f46..febd9039e 100644
--- a/Eigen/src/SparseCore/SparseCompressedBase.h
+++ b/Eigen/src/SparseCore/SparseCompressedBase.h
@@ -224,11 +224,11 @@ class SparseCompressedBase<Derived>::ReverseInnerIterator
       }
       else
       {
-        m_start.value() = mat.outerIndexPtr()[outer];
+        m_start = mat.outerIndexPtr()[outer];
         if(mat.isCompressed())
           m_id = mat.outerIndexPtr()[outer+1];
         else
-          m_id = m_start.value() + mat.innerNonZeroPtr()[outer];
+          m_id = m_start + mat.innerNonZeroPtr()[outer];
       }
     }
 
@@ -254,14 +254,15 @@ class SparseCompressedBase<Derived>::ReverseInnerIterator
     inline Index row() const { return IsRowMajor ? m_outer.value() : index(); }
     inline Index col() const { return IsRowMajor ? index() : m_outer.value(); }
 
-    inline operator bool() const { return (m_id > m_start.value()); }
+    inline operator bool() const { return (m_id > m_start); }
 
   protected:
     const Scalar* m_values;
     const StorageIndex* m_indices;
-    const internal::variable_if_dynamic<Index,Derived::IsVectorAtCompileTime?0:Dynamic> m_outer;
+    typedef internal::variable_if_dynamic<Index,Derived::IsVectorAtCompileTime?0:Dynamic> OuterType;
+    const OuterType m_outer;
     Index m_id;
-    const internal::variable_if_dynamic<Index,Derived::IsVectorAtCompileTime?0:Dynamic> m_start;
+    Index m_start;
 };
 
 namespace internal {
diff --git a/test/sparse_basic.cpp b/test/sparse_basic.cpp
index 7b5f3eb38..552bbac4d 100644
--- a/test/sparse_basic.cpp
+++ b/test/sparse_basic.cpp
@@ -219,6 +219,36 @@ template<typename SparseMatrixType> void sparse_basic(const SparseMatrixType& re
     }
   }
 
+  // test reverse iterators
+  {
+    DenseMatrix refMat2 = DenseMatrix::Zero(rows, cols);
+    SparseMatrixType m2(rows, cols);
+    initSparse<Scalar>(density, refMat2, m2);
+    std::vector<Scalar> ref_value(m2.innerSize());
+    std::vector<Index> ref_index(m2.innerSize());
+    if(internal::random<bool>())
+      m2.makeCompressed();
+    for(Index j = 0; j<m2.outerSize(); ++j)
+    {
+      Index count_forward = 0;
+
+      for(typename SparseMatrixType::InnerIterator it(m2,j); it; ++it)
+      {
+        ref_value[ref_value.size()-1-count_forward] = it.value();
+        ref_index[ref_index.size()-1-count_forward] = it.index();
+        count_forward++;
+      }
+      Index count_reverse = 0;
+      for(typename SparseMatrixType::ReverseInnerIterator it(m2,j); it; --it)
+      {
+        VERIFY_IS_APPROX( std::abs(ref_value[ref_value.size()-count_forward+count_reverse])+1, std::abs(it.value())+1);
+        VERIFY_IS_EQUAL( ref_index[ref_index.size()-count_forward+count_reverse] , it.index());
+        count_reverse++;
+      }
+      VERIFY_IS_EQUAL(count_forward, count_reverse);
+    }
+  }
+
   // test transpose
   {
     DenseMatrix refMat2 = DenseMatrix::Zero(rows, cols);