From 945b80c83e3bb7320667e8a9a45fc4912af85c79 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 6 Oct 2015 11:57:03 +0200
Subject: [PATCH] Optimize Ref<SparseMatrix> by removing useless default
 initialisation of SparseMapBase and SparseMatrix

---
 Eigen/src/SparseCore/SparseMap.h |  6 ++++++
 Eigen/src/SparseCore/SparseRef.h | 12 +++++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/Eigen/src/SparseCore/SparseMap.h b/Eigen/src/SparseCore/SparseMap.h
index 2ef4181bc..058a6d62b 100644
--- a/Eigen/src/SparseCore/SparseMap.h
+++ b/Eigen/src/SparseCore/SparseMap.h
@@ -120,6 +120,9 @@ class SparseMapBase<Derived,ReadOnlyAccessors>
 
     /** Empty destructor */
     inline ~SparseMapBase() {}
+
+  protected:
+    inline SparseMapBase() {}
 };
 
 template<typename Derived>
@@ -172,6 +175,9 @@ class SparseMapBase<Derived,WriteAccessors>
 
     /** Empty destructor */
     inline ~SparseMapBase() {}
+
+  protected:
+    inline SparseMapBase() {}
 };
 
 template<typename MatScalar, int MatOptions, typename MatIndex, int Options, typename StrideType>
diff --git a/Eigen/src/SparseCore/SparseRef.h b/Eigen/src/SparseCore/SparseRef.h
index 08268b9e1..fbd489a13 100644
--- a/Eigen/src/SparseCore/SparseRef.h
+++ b/Eigen/src/SparseCore/SparseRef.h
@@ -182,8 +182,9 @@ class Ref<const SparseMatrix<MatScalar,MatOptions,MatIndex>, Options, StrideType
     {
       if((Options & int(StandardCompressedFormat)) && (!expr.isCompressed()))
       {
-        m_object = expr;
-        Base::construct(m_object);
+        TPlainObjectType* obj = reinterpret_cast<TPlainObjectType*>(m_object_bytes);
+        ::new (obj) TPlainObjectType(expr);
+        Base::construct(*obj);
       }
       else
       {
@@ -194,12 +195,13 @@ class Ref<const SparseMatrix<MatScalar,MatOptions,MatIndex>, Options, StrideType
     template<typename Expression>
     void construct(const Expression& expr, internal::false_type)
     {
-      m_object = expr;
-      Base::construct(m_object);
+      TPlainObjectType* obj = reinterpret_cast<TPlainObjectType*>(m_object_bytes);
+      ::new (obj) TPlainObjectType(expr);
+      Base::construct(*obj);
     }
 
   protected:
-    TPlainObjectType m_object;
+    char m_object_bytes[sizeof(TPlainObjectType)];
 };