hessenberg.hpp

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//
// Copyright (c) 2021-2023, University of Colorado Denver. All rights reserved.
//
// This file is part of <T>LAPACK.
// <T>LAPACK is free software: you can redistribute it and/or modify it under
// the terms of the BSD 3-Clause license. See the accompanying LICENSE file.
 
#ifndef TLAPACK_HESSENBERG_HH
#define TLAPACK_HESSENBERG_HH
 
#include "tlapack/base/utils.hpp"
#include "tlapack/lapack/gehd2.hpp"
#include "tlapack/lapack/gehrd.hpp"
 
namespace tlapack {
 
enum class HessenbergVariant : char { Level2 = '2', Blocked = 'B' };
 
struct HessenbergOpts : public GehrdOpts {
    HessenbergVariant variant = HessenbergVariant::Blocked;
};
 
template <class T, TLAPACK_SMATRIX matrix_t, TLAPACK_SVECTOR vector_t>
constexpr WorkInfo hessenberg_worksize(size_type<matrix_t> ilo,
                                       size_type<matrix_t> ihi,
                                       const matrix_t& A,
                                       const vector_t& tau,
                                       const HessenbergOpts& opts = {})
{
    // Call variant
    if (opts.variant == HessenbergVariant::Level2)
        return gehd2_worksize<T>(ilo, ihi, A, tau);
    else
        return gehrd_worksize<T>(ilo, ihi, A, tau, opts);
}
 
template <TLAPACK_SMATRIX matrix_t,
          TLAPACK_SVECTOR vector_t,
          TLAPACK_WORKSPACE work_t>
int hessenberg_work(size_type<matrix_t> ilo,
                    size_type<matrix_t> ihi,
                    matrix_t& A,
                    vector_t& tau,
                    work_t& work,
                    const HessenbergOpts& opts = {})
{
    // Call variant
    if (opts.variant == HessenbergVariant::Level2)
        return gehd2_work(ilo, ihi, A, tau, work);
    else
        return gehrd_work(ilo, ihi, A, tau, work, opts);
}
 
template <TLAPACK_SMATRIX matrix_t, TLAPACK_SVECTOR vector_t>
int hessenberg(size_type<matrix_t> ilo,
               size_type<matrix_t> ihi,
               matrix_t& A,
               vector_t& tau,
               const HessenbergOpts& opts = {})
{
    // Call variant
    if (opts.variant == HessenbergVariant::Level2)
        return gehd2(ilo, ihi, A, tau);
    else
        return gehrd(ilo, ihi, A, tau, opts);
}
 
}  // namespace tlapack
 
#endif