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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
// Copyright 2008-2016 National ICT Australia (NICTA)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ------------------------------------------------------------------------
namespace newarp
{
//! Calculate the eigenvalues and eigenvectors of a symmetric tridiagonal matrix.
//! This class is a wrapper of the Lapack functions `_steqr`.
template<typename eT>
class TridiagEigen
{
private:
blas_int n;
Col<eT> main_diag; // Main diagonal elements of the matrix
Col<eT> sub_diag; // Sub-diagonal elements of the matrix
Mat<eT> evecs; // To store eigenvectors
bool computed;
public:
//! Default constructor. Computation can
//! be performed later by calling the compute() method.
inline TridiagEigen();
//! Constructor to create an object that calculates the eigenvalues
//! and eigenvectors of a symmetric tridiagonal matrix `mat_obj`.
inline TridiagEigen(const Mat<eT>& mat_obj);
//! Compute the eigenvalue decomposition of a symmetric tridiagonal matrix.
inline void compute(const Mat<eT>& mat_obj);
//! Retrieve the eigenvalues.
inline Col<eT> eigenvalues();
//! Retrieve the eigenvectors.
inline Mat<eT> eigenvectors();
};
} // namespace newarp
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