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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
{
template<typename eT>
inline
TridiagEigen<eT>::TridiagEigen()
: n(0)
, computed(false)
{
arma_extra_debug_sigprint();
}
template<typename eT>
inline
TridiagEigen<eT>::TridiagEigen(const Mat<eT>& mat_obj)
: n(mat_obj.n_rows)
, computed(false)
{
arma_extra_debug_sigprint();
compute(mat_obj);
}
template<typename eT>
inline
void
TridiagEigen<eT>::compute(const Mat<eT>& mat_obj)
{
arma_extra_debug_sigprint();
arma_debug_check( (mat_obj.is_square() == false), "newarp::TridiagEigen::compute(): matrix must be square" );
n = blas_int(mat_obj.n_rows);
main_diag = mat_obj.diag();
sub_diag = mat_obj.diag(-1);
evecs.set_size(n, n);
char compz = 'I';
blas_int lwork_min = 1 + 4*n + n*n;
blas_int liwork_min = 3 + 5*n;
blas_int info = blas_int(0);
blas_int lwork_proposed = 0;
blas_int liwork_proposed = 0;
if(n >= 32)
{
eT work_query[2] = {};
blas_int lwork_query = blas_int(-1);
blas_int iwork_query[2] = {};
blas_int liwork_query = blas_int(-1);
arma_extra_debug_print("lapack::stedc()");
lapack::stedc(&compz, &n, main_diag.memptr(), sub_diag.memptr(), evecs.memptr(), &n, &work_query[0], &lwork_query, &iwork_query[0], &liwork_query, &info);
if(info != 0) { arma_stop_runtime_error("lapack::stedc(): couldn't get size of work arrays"); return; }
lwork_proposed = static_cast<blas_int>( work_query[0] );
liwork_proposed = iwork_query[0];
}
blas_int lwork = (std::max)( lwork_min, lwork_proposed);
blas_int liwork = (std::max)(liwork_min, liwork_proposed);
podarray<eT> work( static_cast<uword>( lwork) );
podarray<blas_int> iwork( static_cast<uword>(liwork) );
arma_extra_debug_print("lapack::stedc()");
lapack::stedc(&compz, &n, main_diag.memptr(), sub_diag.memptr(), evecs.memptr(), &n, work.memptr(), &lwork, iwork.memptr(), &liwork, &info);
if(info != 0) { arma_stop_runtime_error("lapack::stedc(): failed to compute all eigenvalues"); return; }
computed = true;
}
template<typename eT>
inline
Col<eT>
TridiagEigen<eT>::eigenvalues()
{
arma_extra_debug_sigprint();
arma_debug_check( (computed == false), "newarp::TridiagEigen::eigenvalues(): need to call compute() first" );
// After calling compute(), main_diag will contain the eigenvalues.
return main_diag;
}
template<typename eT>
inline
Mat<eT>
TridiagEigen<eT>::eigenvectors()
{
arma_extra_debug_sigprint();
arma_debug_check( (computed == false), "newarp::TridiagEigen::eigenvectors(): need to call compute() first" );
return evecs;
}
} // namespace newarp
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