getrs.hpp

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// Copyright (c) 2021--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 "../concepts.hpp"
#include "../declarations.hpp"
#include "../macros.hpp"
#include "../mem/address_space.hpp"
#include "../traits.hpp"
 
#ifndef NDA_HAVE_DEVICE
#include "../device.hpp"
#endif // NDA_HAVE_DEVICE
 
#include <type_traits>
 
namespace nda::lapack {

  template <Matrix A, MemoryArray B, MemoryVector IPIV>
    requires((MemoryMatrix<A> or is_conj_array_expr<A>)
             and have_same_value_type_v<A, B> and mem::have_compatible_addr_space<A, B, IPIV> and is_blas_lapack_v<get_value_t<A>>)
  int getrs(A const &a, B &&b, IPIV const &ipiv) { // NOLINT (temporary views are allowed here)
    static_assert(std::is_same_v<get_value_t<IPIV>, int>, "Error in nda::lapack::getrs: Pivoting array must have elements of type int");
    static_assert(get_rank<B> == 1 || get_rank<B> == 2, "Error in nda::lapack::getrs: Right hand side must have rank 1 or 2");
    static_assert(has_F_layout<B>, "Error in nda::lapack::getrs: B must have Fortran layout");
 
    // get underlying matrix in case it is given as a lazy conjugate expression
    auto &a_mat = get_array(a);
 
    // check the dimensions of the input/output arrays/views
    EXPECTS(a_mat.shape()[0] == a_mat.shape()[1]);
    EXPECTS(b.extent(0) == a_mat.shape()[0]);
    EXPECTS(ipiv.size() == a_mat.shape()[0]);
 
    // arrays/views must be LAPACK compatible
    EXPECTS(a_mat.indexmap().min_stride() == 1);
    EXPECTS(b.indexmap().min_stride() == 1);
    EXPECTS(ipiv.indexmap().min_stride() == 1);
 
    // perform actual library call
    int info = 0;
    if constexpr (mem::have_device_compatible_addr_space<A, B, IPIV>) {
#if defined(NDA_HAVE_DEVICE)
      device::getrs(get_op<A>, get_ncols(a_mat), get_ncols(b), a_mat.data(), get_ld(a_mat), ipiv.data(), b.data(), get_ld(b), info);
#else
      compile_error_no_gpu();
#endif
    } else {
      f77::getrs(get_op<A>, get_ncols(a_mat), get_ncols(b), a_mat.data(), get_ld(a_mat), ipiv.data(), b.data(), get_ld(b), info);
    }
 
    return info;
  }
 
} // namespace nda::lapack