* Refactoring of the class hierarchy: introduction of DenseDirectAccessBase, removal of extra _Base/_Options template parameters.

* Introduction of strides-at-compile-time so for example the optimized code really knows when it needs to evaluate to a temporary
* StorageKind / XprKind
* Quaternion::setFromTwoVectors: use JacobiSVD instead of SVD
* ComplexSchur: support the 1x1 case

Eigen/src/Core/util/BlasUtil.h

@@ -158,7 +158,9 @@ template<typename XprType> struct ei_blas_traits
     IsComplex = NumTraits<Scalar>::IsComplex,
     IsTransposed = false,
     NeedToConjugate = false,
-    ActualAccess = int(ei_traits<XprType>::Flags)&DirectAccessBit ? HasDirectAccess : NoDirectAccess
+    ActualAccess = (    (int(ei_traits<XprType>::Flags)&DirectAccessBit)
+                     && (int(ei_inner_stride_at_compile_time<XprType>::ret) == 1)
+                   ) ?  HasDirectAccess : NoDirectAccess
   };
   typedef typename ei_meta_if<int(ActualAccess)==HasDirectAccess,
     ExtractType,

Eigen/src/Core/util/Constants.h

@@ -97,8 +97,6 @@ const unsigned int EvalBeforeAssigningBit = 0x4;
   */
 const unsigned int PacketAccessBit = 0x8;
 
-const unsigned int NestByRefBit = 0x100;
-
 #ifdef EIGEN_VECTORIZE
 /** \ingroup flags
   *
@@ -151,6 +149,7 @@ const unsigned int DirectAccessBit = 0x20;
   * means the first coefficient packet is guaranteed to be aligned */
 const unsigned int AlignedBit = 0x40;
 
+const unsigned int NestByRefBit = 0x100;
 
 // list of flags that are inherited by default
 const unsigned int HereditaryBits = RowMajorBit
@@ -266,9 +265,15 @@ namespace Architecture
   };
 }
 
-enum DenseStorageMatrix {};
-enum DenseStorageArray {};
-
 enum { CoeffBasedProductMode, LazyCoeffBasedProductMode, OuterProduct, InnerProduct, GemvProduct, GemmProduct };
 
+/** The type used to identify a dense storage. */
+struct Dense {};
+
+/** The type used to identify a matrix expression */
+struct MatrixXpr {};
+
+/** The type used to identify an array expression */
+struct ArrayXpr {};
+
 #endif // EIGEN_CONSTANTS_H

Eigen/src/Core/util/ForwardDeclarations.h

@@ -40,6 +40,9 @@ template<typename _Scalar, int _Rows, int _Cols,
          int _MaxCols = _Cols
 > class Matrix;
 
+template<typename Derived> class MatrixBase;
+template<typename Derived> class ArrayBase;
+
 template<typename ExpressionType, unsigned int Added, unsigned int Removed> class Flagged;
 template<typename ExpressionType, template <typename> class StorageBase > class NoAlias;
 template<typename ExpressionType> class NestByValue;

Eigen/src/Core/util/XprHelper.h

@@ -136,14 +136,14 @@ template<int _Rows, int _Cols> struct ei_size_at_compile_time
  * whereas ei_eval is a const reference in the case of a matrix
  */
 
-template<typename T, typename StorageType = typename ei_traits<T>::StorageType> struct ei_plain_matrix_type;
+template<typename T, typename StorageKind = typename ei_traits<T>::StorageKind> struct ei_plain_matrix_type;
 template<typename T, typename BaseClassType> struct ei_plain_matrix_type_dense;
 template<typename T> struct ei_plain_matrix_type<T,Dense>
 {
-  typedef typename ei_plain_matrix_type_dense<T,typename ei_traits<T>::DenseStorageType>::type type;
+  typedef typename ei_plain_matrix_type_dense<T,typename ei_traits<T>::XprKind>::type type;
 };
 
-template<typename T> struct ei_plain_matrix_type_dense<T,DenseStorageMatrix>
+template<typename T> struct ei_plain_matrix_type_dense<T,MatrixXpr>
 {
   typedef Matrix<typename ei_traits<T>::Scalar,
                 ei_traits<T>::RowsAtCompileTime,
@@ -154,7 +154,7 @@ template<typename T> struct ei_plain_matrix_type_dense<T,DenseStorageMatrix>
           > type;
 };
 
-template<typename T> struct ei_plain_matrix_type_dense<T,DenseStorageArray>
+template<typename T> struct ei_plain_matrix_type_dense<T,ArrayXpr>
 {
   typedef Array<typename ei_traits<T>::Scalar,
                 ei_traits<T>::RowsAtCompileTime,
@@ -169,7 +169,7 @@ template<typename T> struct ei_plain_matrix_type_dense<T,DenseStorageArray>
  * in order to avoid a useless copy
  */
 
-template<typename T, typename StorageType = typename ei_traits<T>::StorageType> struct ei_eval;
+template<typename T, typename StorageKind = typename ei_traits<T>::StorageKind> struct ei_eval;
 
 template<typename T> struct ei_eval<T,Dense>
 {
@@ -204,14 +204,16 @@ struct ei_eval<Array<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>, Dense
 template<typename T> struct ei_plain_matrix_type_column_major
 {
   enum { Rows = ei_traits<T>::RowsAtCompileTime,
-         Cols = ei_traits<T>::ColsAtCompileTime
+         Cols = ei_traits<T>::ColsAtCompileTime,
+         MaxRows = ei_traits<T>::MaxRowsAtCompileTime,
+         MaxCols = ei_traits<T>::MaxColsAtCompileTime
   };
   typedef Matrix<typename ei_traits<T>::Scalar,
                 Rows,
                 Cols,
-                (Rows==1&&Cols!=1) ? RowMajor : ColMajor,
-                ei_traits<T>::MaxRowsAtCompileTime,
-                ei_traits<T>::MaxColsAtCompileTime
+                (MaxRows==1&&MaxCols!=1) ? RowMajor : ColMajor,
+                MaxRows,
+                MaxCols
           > type;
 };
 
@@ -220,14 +222,16 @@ template<typename T> struct ei_plain_matrix_type_column_major
 template<typename T> struct ei_plain_matrix_type_row_major
 {
   enum { Rows = ei_traits<T>::RowsAtCompileTime,
-         Cols = ei_traits<T>::ColsAtCompileTime
+         Cols = ei_traits<T>::ColsAtCompileTime,
+         MaxRows = ei_traits<T>::MaxRowsAtCompileTime,
+         MaxCols = ei_traits<T>::MaxColsAtCompileTime
   };
   typedef Matrix<typename ei_traits<T>::Scalar,
                 Rows,
                 Cols,
-                (Cols==1&&Rows!=1) ? ColMajor : RowMajor,
-                ei_traits<T>::MaxRowsAtCompileTime,
-                ei_traits<T>::MaxColsAtCompileTime
+                (MaxCols==1&&MaxRows!=1) ? RowMajor : ColMajor,
+                MaxRows,
+                MaxCols
           > type;
 };