Kernel.h
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00001 // This file is part of Eigen, a lightweight C++ template library
00002 // for linear algebra.
00003 //
00004 // Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
00005 //
00006 // Eigen is free software; you can redistribute it and/or
00007 // modify it under the terms of the GNU Lesser General Public
00008 // License as published by the Free Software Foundation; either
00009 // version 3 of the License, or (at your option) any later version.
00010 //
00011 // Alternatively, you can redistribute it and/or
00012 // modify it under the terms of the GNU General Public License as
00013 // published by the Free Software Foundation; either version 2 of
00014 // the License, or (at your option) any later version.
00015 //
00016 // Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
00017 // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
00018 // FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the
00019 // GNU General Public License for more details.
00020 //
00021 // You should have received a copy of the GNU Lesser General Public
00022 // License and a copy of the GNU General Public License along with
00023 // Eigen. If not, see <http://www.gnu.org/licenses/>.
00024 
00025 #ifndef EIGEN_MISC_KERNEL_H
00026 #define EIGEN_MISC_KERNEL_H
00027 
00028 namespace Eigen { 
00029 
00030 namespace internal {
00031 
00035 template<typename DecompositionType>
00036 struct traits<kernel_retval_base<DecompositionType> >
00037 {
00038   typedef typename DecompositionType::MatrixType MatrixType;
00039   typedef Matrix<
00040     typename MatrixType::Scalar,
00041     MatrixType::ColsAtCompileTime, // the number of rows in the "kernel matrix"
00042                                    // is the number of cols of the original matrix
00043                                    // so that the product "matrix * kernel = zero" makes sense
00044     Dynamic,                       // we don't know at compile-time the dimension of the kernel
00045     MatrixType::Options,
00046     MatrixType::MaxColsAtCompileTime, // see explanation for 2nd template parameter
00047     MatrixType::MaxColsAtCompileTime // the kernel is a subspace of the domain space,
00048                                      // whose dimension is the number of columns of the original matrix
00049   > ReturnType;
00050 };
00051 
00052 template<typename _DecompositionType> struct kernel_retval_base
00053  : public ReturnByValue<kernel_retval_base<_DecompositionType> >
00054 {
00055   typedef _DecompositionType DecompositionType;
00056   typedef ReturnByValue<kernel_retval_base> Base;
00057   typedef typename Base::Index Index;
00058 
00059   kernel_retval_base(const DecompositionType& dec)
00060     : m_dec(dec),
00061       m_rank(dec.rank()),
00062       m_cols(m_rank==dec.cols() ? 1 : dec.cols() - m_rank)
00063   {}
00064 
00065   inline Index rows() const { return m_dec.cols(); }
00066   inline Index cols() const { return m_cols; }
00067   inline Index rank() const { return m_rank; }
00068   inline const DecompositionType& dec() const { return m_dec; }
00069 
00070   template<typename Dest> inline void evalTo(Dest& dst) const
00071   {
00072     static_cast<const kernel_retval<DecompositionType>*>(this)->evalTo(dst);
00073   }
00074 
00075   protected:
00076     const DecompositionType& m_dec;
00077     Index m_rank, m_cols;
00078 };
00079 
00080 } // end namespace internal
00081 
00082 #define EIGEN_MAKE_KERNEL_HELPERS(DecompositionType) \
00083   typedef typename DecompositionType::MatrixType MatrixType; \
00084   typedef typename MatrixType::Scalar Scalar; \
00085   typedef typename MatrixType::RealScalar RealScalar; \
00086   typedef typename MatrixType::Index Index; \
00087   typedef Eigen::internal::kernel_retval_base<DecompositionType> Base; \
00088   using Base::dec; \
00089   using Base::rank; \
00090   using Base::rows; \
00091   using Base::cols; \
00092   kernel_retval(const DecompositionType& dec) : Base(dec) {}
00093 
00094 } // end namespace Eigen
00095 
00096 #endif // EIGEN_MISC_KERNEL_H