gelss.hpp

Go to the documentation of this file.

// Copyright (c) 2020--present, The Simons Foundation
// This file is part of TRIQS/nda and is licensed under the Apache License, Version 2.0.
// SPDX-License-Identifier: Apache-2.0
// See LICENSE in the root of this distribution for details.

 
#pragma once
 
#include "./interface/cxx_interface.hpp"
#include "../basic_array.hpp"
#include "../basic_functions.hpp"
#include "../blas/tools.hpp"
#include "../concepts.hpp"
#include "../declarations.hpp"
#include "../macros.hpp"
#include "../mem/address_space.hpp"
#include "../traits.hpp"
 
#include <algorithm>
#include <cmath>
#include <complex>
#include <type_traits>
 
namespace nda::lapack {

  template <BlasArray<2> A, BlasArrayFor<A> B, BlasArrayRealFor<A, 1> S, BlasArrayFor<A, 1> W1 = vector_value_t<A>,
            BlasArrayRealFor<A, 1> W2 = vector_fp_t<A>>
    requires(mem::have_host_compatible_addr_space<A> and (get_rank<B> == 1 or get_rank<B> == 2) and has_F_layout<A, B>)
  int gelss(A &&a, B &&b, S &&s, get_fp_t<A> rcond, int &rank, W1 &&work = vector_value_t<A>{}, W2 &&rwork = vector_fp_t<A>{}) { // NOLINT
    // check the dimensions of the input/output arrays/views and resize if necessary
    auto const [m, n] = a.shape();
    auto const k      = std::min(m, n);
    resize_or_check_if_view(s, {k});
    resize_or_check_work_buffer(rwork, 5 * k);
    EXPECTS(b.extent(0) >= std::max(m, n));
 
    // arrays/views must be LAPACK compatible
    EXPECTS(a.indexmap().min_stride() == 1);
    EXPECTS(b.indexmap().min_stride() == 1);
    EXPECTS(s.indexmap().min_stride() == 1);
 
    // first call to get the optimal buffer size
    auto tmp_lwork = get_value_t<A>{};
    int info       = 0;
    int nrhs       = (get_rank<B> == 2 ? b.extent(1) : 1);
    f77::gelss(m, n, nrhs, a.data(), get_ld(a), b.data(), get_ld(b), s.data(), rcond, rank, &tmp_lwork, -1, rwork.data(), info);
    int lwork = static_cast<int>(std::ceil(std::real(tmp_lwork)));
 
    // resize/check work buffer
    resize_or_check_work_buffer(work, lwork);
 
    // perform actual library call
    f77::gelss(m, n, nrhs, a.data(), get_ld(a), b.data(), get_ld(b), s.data(), rcond, rank, work.data(), lwork, rwork.data(), info);
 
    return info;
  }
 
} // namespace nda::lapack