96 lines
2.6 KiB
C++
96 lines
2.6 KiB
C++
// Copyright (C) 2020-2022 Yixuan Qiu <yixuan.qiu@cos.name>
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//
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// This Source Code Form is subject to the terms of the Mozilla
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// Public License v. 2.0. If a copy of the MPL was not distributed
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// with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
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#ifndef SPECTRA_SYM_GEIGS_SHIFT_INVERT_OP_H
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#define SPECTRA_SYM_GEIGS_SHIFT_INVERT_OP_H
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#include <Eigen/Core>
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#include "../SymShiftInvert.h"
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#include "../SparseSymMatProd.h"
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namespace Spectra {
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///
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/// \ingroup Operators
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///
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/// This class defines the matrix operation for generalized eigen solver in the
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/// shift-and-invert mode. It computes \f$y=(A-\sigma B)^{-1}Bx\f$ for any
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/// vector \f$x\f$, where \f$A\f$ is a symmetric matrix, \f$B\f$ is positive definite,
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/// and \f$\sigma\f$ is a real shift.
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/// This class is intended for internal use.
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///
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template <typename OpType = SymShiftInvert<double>,
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typename BOpType = SparseSymMatProd<double>>
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class SymGEigsShiftInvertOp
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{
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public:
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using Scalar = typename OpType::Scalar;
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private:
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using Index = Eigen::Index;
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using Vector = Eigen::Matrix<Scalar, Eigen::Dynamic, 1>;
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OpType& m_op;
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const BOpType& m_Bop;
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mutable Vector m_cache; // temporary working space
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public:
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///
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/// Constructor to create the matrix operation object.
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///
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/// \param op The \f$(A-\sigma B)^{-1}\f$ matrix operation object.
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/// \param Bop The \f$B\f$ matrix operation object.
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///
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SymGEigsShiftInvertOp(OpType& op, const BOpType& Bop) :
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m_op(op), m_Bop(Bop), m_cache(op.rows())
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{}
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///
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/// Move constructor.
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///
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SymGEigsShiftInvertOp(SymGEigsShiftInvertOp&& other) :
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m_op(other.m_op), m_Bop(other.m_Bop)
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{
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// We emulate the move constructor for Vector using Vector::swap()
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m_cache.swap(other.m_cache);
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}
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///
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/// Return the number of rows of the underlying matrix.
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///
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Index rows() const { return m_op.rows(); }
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///
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/// Return the number of columns of the underlying matrix.
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///
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Index cols() const { return m_op.rows(); }
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///
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/// Set the real shift \f$\sigma\f$.
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///
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void set_shift(const Scalar& sigma)
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{
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m_op.set_shift(sigma);
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}
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///
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/// Perform the matrix operation \f$y=(A-\sigma B)^{-1}Bx\f$.
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///
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/// \param x_in Pointer to the \f$x\f$ vector.
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/// \param y_out Pointer to the \f$y\f$ vector.
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///
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// y_out = inv(A - sigma * B) * B * x_in
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void perform_op(const Scalar* x_in, Scalar* y_out) const
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{
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m_Bop.perform_op(x_in, m_cache.data());
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m_op.perform_op(m_cache.data(), y_out);
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}
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};
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} // namespace Spectra
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#endif // SPECTRA_SYM_GEIGS_SHIFT_INVERT_OP_H
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