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- // This file is part of Eigen, a lightweight C++ template library
- // for linear algebra.
- //
- // Copyright (C) 2010 Vincent Lejeune
- // Copyright (C) 2010 Gael Guennebaud <gael.guennebaud@inria.fr>
- //
- // This Source Code Form is subject to the terms of the Mozilla
- // Public License v. 2.0. If a copy of the MPL was not distributed
- // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
- #ifndef EIGEN_BLOCK_HOUSEHOLDER_H
- #define EIGEN_BLOCK_HOUSEHOLDER_H
- // This file contains some helper function to deal with block householder reflectors
- namespace Eigen {
- namespace internal {
-
- /** \internal */
- // template<typename TriangularFactorType,typename VectorsType,typename CoeffsType>
- // void make_block_householder_triangular_factor(TriangularFactorType& triFactor, const VectorsType& vectors, const CoeffsType& hCoeffs)
- // {
- // typedef typename VectorsType::Scalar Scalar;
- // const Index nbVecs = vectors.cols();
- // eigen_assert(triFactor.rows() == nbVecs && triFactor.cols() == nbVecs && vectors.rows()>=nbVecs);
- //
- // for(Index i = 0; i < nbVecs; i++)
- // {
- // Index rs = vectors.rows() - i;
- // // Warning, note that hCoeffs may alias with vectors.
- // // It is then necessary to copy it before modifying vectors(i,i).
- // typename CoeffsType::Scalar h = hCoeffs(i);
- // // This hack permits to pass trough nested Block<> and Transpose<> expressions.
- // Scalar *Vii_ptr = const_cast<Scalar*>(vectors.data() + vectors.outerStride()*i + vectors.innerStride()*i);
- // Scalar Vii = *Vii_ptr;
- // *Vii_ptr = Scalar(1);
- // triFactor.col(i).head(i).noalias() = -h * vectors.block(i, 0, rs, i).adjoint()
- // * vectors.col(i).tail(rs);
- // *Vii_ptr = Vii;
- // // FIXME add .noalias() once the triangular product can work inplace
- // triFactor.col(i).head(i) = triFactor.block(0,0,i,i).template triangularView<Upper>()
- // * triFactor.col(i).head(i);
- // triFactor(i,i) = hCoeffs(i);
- // }
- // }
- /** \internal */
- // This variant avoid modifications in vectors
- template<typename TriangularFactorType,typename VectorsType,typename CoeffsType>
- void make_block_householder_triangular_factor(TriangularFactorType& triFactor, const VectorsType& vectors, const CoeffsType& hCoeffs)
- {
- const Index nbVecs = vectors.cols();
- eigen_assert(triFactor.rows() == nbVecs && triFactor.cols() == nbVecs && vectors.rows()>=nbVecs);
- for(Index i = nbVecs-1; i >=0 ; --i)
- {
- Index rs = vectors.rows() - i - 1;
- Index rt = nbVecs-i-1;
- if(rt>0)
- {
- triFactor.row(i).tail(rt).noalias() = -hCoeffs(i) * vectors.col(i).tail(rs).adjoint()
- * vectors.bottomRightCorner(rs, rt).template triangularView<UnitLower>();
-
- // FIXME add .noalias() once the triangular product can work inplace
- triFactor.row(i).tail(rt) = triFactor.row(i).tail(rt) * triFactor.bottomRightCorner(rt,rt).template triangularView<Upper>();
-
- }
- triFactor(i,i) = hCoeffs(i);
- }
- }
- /** \internal
- * if forward then perform mat = H0 * H1 * H2 * mat
- * otherwise perform mat = H2 * H1 * H0 * mat
- */
- template<typename MatrixType,typename VectorsType,typename CoeffsType>
- void apply_block_householder_on_the_left(MatrixType& mat, const VectorsType& vectors, const CoeffsType& hCoeffs, bool forward)
- {
- enum { TFactorSize = MatrixType::ColsAtCompileTime };
- Index nbVecs = vectors.cols();
- Matrix<typename MatrixType::Scalar, TFactorSize, TFactorSize, RowMajor> T(nbVecs,nbVecs);
-
- if(forward) make_block_householder_triangular_factor(T, vectors, hCoeffs);
- else make_block_householder_triangular_factor(T, vectors, hCoeffs.conjugate());
- const TriangularView<const VectorsType, UnitLower> V(vectors);
- // A -= V T V^* A
- Matrix<typename MatrixType::Scalar,VectorsType::ColsAtCompileTime,MatrixType::ColsAtCompileTime,
- (VectorsType::MaxColsAtCompileTime==1 && MatrixType::MaxColsAtCompileTime!=1)?RowMajor:ColMajor,
- VectorsType::MaxColsAtCompileTime,MatrixType::MaxColsAtCompileTime> tmp = V.adjoint() * mat;
- // FIXME add .noalias() once the triangular product can work inplace
- if(forward) tmp = T.template triangularView<Upper>() * tmp;
- else tmp = T.template triangularView<Upper>().adjoint() * tmp;
- mat.noalias() -= V * tmp;
- }
- } // end namespace internal
- } // end namespace Eigen
- #endif // EIGEN_BLOCK_HOUSEHOLDER_H
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