1 // This file is part of Eigen, a lightweight C++ template library
2 // for linear algebra.
3 //
4 // Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
5 //
6 // This Source Code Form is subject to the terms of the Mozilla
7 // Public License v. 2.0. If a copy of the MPL was not distributed
8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9 
10 #ifndef EIGEN_MISC_KERNEL_H
11 #define EIGEN_MISC_KERNEL_H
12 
13 namespace Eigen {
14 
15 namespace internal {
16 
17 /** \class kernel_retval_base
18   *
19   */
20 template<typename DecompositionType>
21 struct traits<kernel_retval_base<DecompositionType> >
22 {
23   typedef typename DecompositionType::MatrixType MatrixType;
24   typedef Matrix<
25     typename MatrixType::Scalar,
26     MatrixType::ColsAtCompileTime, // the number of rows in the "kernel matrix"
27                                    // is the number of cols of the original matrix
28                                    // so that the product "matrix * kernel = zero" makes sense
29     Dynamic,                       // we don't know at compile-time the dimension of the kernel
30     MatrixType::Options,
31     MatrixType::MaxColsAtCompileTime, // see explanation for 2nd template parameter
32     MatrixType::MaxColsAtCompileTime // the kernel is a subspace of the domain space,
33                                      // whose dimension is the number of columns of the original matrix
34   > ReturnType;
35 };
36 
37 template<typename _DecompositionType> struct kernel_retval_base
38  : public ReturnByValue<kernel_retval_base<_DecompositionType> >
39 {
40   typedef _DecompositionType DecompositionType;
41   typedef ReturnByValue<kernel_retval_base> Base;
42   typedef typename Base::Index Index;
43 
44   kernel_retval_base(const DecompositionType& dec)
45     : m_dec(dec),
46       m_rank(dec.rank()),
47       m_cols(m_rank==dec.cols() ? 1 : dec.cols() - m_rank)
48   {}
49 
50   inline Index rows() const { return m_dec.cols(); }
51   inline Index cols() const { return m_cols; }
52   inline Index rank() const { return m_rank; }
53   inline const DecompositionType& dec() const { return m_dec; }
54 
55   template<typename Dest> inline void evalTo(Dest& dst) const
56   {
57     static_cast<const kernel_retval<DecompositionType>*>(this)->evalTo(dst);
58   }
59 
60   protected:
61     const DecompositionType& m_dec;
62     Index m_rank, m_cols;
63 };
64 
65 } // end namespace internal
66 
67 #define EIGEN_MAKE_KERNEL_HELPERS(DecompositionType) \
68   typedef typename DecompositionType::MatrixType MatrixType; \
69   typedef typename MatrixType::Scalar Scalar; \
70   typedef typename MatrixType::RealScalar RealScalar; \
71   typedef typename MatrixType::Index Index; \
72   typedef Eigen::internal::kernel_retval_base<DecompositionType> Base; \
73   using Base::dec; \
74   using Base::rank; \
75   using Base::rows; \
76   using Base::cols; \
77   kernel_retval(const DecompositionType& dec) : Base(dec) {}
78 
79 } // end namespace Eigen
80 
81 #endif // EIGEN_MISC_KERNEL_H
82