Kokkos_Pair.hpp

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//@HEADER
// ************************************************************************
//
//                        Kokkos v. 4.0
//       Copyright (2022) National Technology & Engineering
//               Solutions of Sandia, LLC (NTESS).
//
// Under the terms of Contract DE-NA0003525 with NTESS,
// the U.S. Government retains certain rights in this software.
//
// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
// See https://kokkos.org/LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//@HEADER


#ifndef KOKKOS_PAIR_HPP
#define KOKKOS_PAIR_HPP
#ifndef KOKKOS_IMPL_PUBLIC_INCLUDE
#define KOKKOS_IMPL_PUBLIC_INCLUDE
#define KOKKOS_IMPL_PUBLIC_INCLUDE_NOTDEFINED_PAIR
#endif

#include <Kokkos_Macros.hpp>
#include <utility>

namespace Kokkos {
template <class T1, class T2>
struct pair {
  using first_type = T1;
  using second_type = T2;

  first_type first;
  second_type second;

  KOKKOS_DEFAULTED_FUNCTION constexpr pair() = default;

#ifdef KOKKOS_COMPILER_NVHPC  // FIXME_NVHPC bug in NVHPC regarding constexpr
                              // constructors used in device code
  KOKKOS_FORCEINLINE_FUNCTION
#else
  KOKKOS_FORCEINLINE_FUNCTION constexpr
#endif
  pair(first_type const& f, second_type const& s) : first(f), second(s) {}

  template <class U, class V>
#ifdef KOKKOS_COMPILER_NVHPC  // FIXME_NVHPC bug in NVHPC regarding constexpr
                              // constructors used in device code
  KOKKOS_FORCEINLINE_FUNCTION
#else
  KOKKOS_FORCEINLINE_FUNCTION constexpr
#endif
  pair(const pair<U, V>& p)
      : first(p.first), second(p.second) {
  }

#ifdef KOKKOS_ENABLE_DEPRECATED_CODE_4
  template <class U, class V>
  KOKKOS_DEPRECATED KOKKOS_FORCEINLINE_FUNCTION constexpr pair(
      const volatile pair<U, V>& p)
      : first(p.first), second(p.second) {}
#endif

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION pair<T1, T2>& operator=(const pair<U, V>& p) {
    first  = p.first;
    second = p.second;
    return *this;
  }

#ifdef KOKKOS_ENABLE_DEPRECATED_CODE_4
  template <class U, class V>
  KOKKOS_DEPRECATED KOKKOS_FORCEINLINE_FUNCTION void operator=(
      const volatile pair<U, V>& p) volatile {
    first  = p.first;
    second = p.second;
    // We deliberately do not return anything here.  See explanation
    // in public documentation above.
  }
#endif

  // from std::pair<U,V>
  template <class U, class V>
  pair(const std::pair<U, V>& p) : first(p.first), second(p.second) {}

  std::pair<T1, T2> to_std_pair() const {
    return std::make_pair(first, second);
  }
};

template <class T1, class T2>
struct pair<T1&, T2&> {
  using first_type = T1&;
  using second_type = T2&;

  first_type first;
  second_type second;

  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(first_type f, second_type s)
      : first(f), second(s) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const pair<U, V>& p)
      : first(p.first), second(p.second) {}

  // from std::pair<U,V>
  template <class U, class V>
  pair(const std::pair<U, V>& p) : first(p.first), second(p.second) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION pair<first_type, second_type>& operator=(
      const pair<U, V>& p) {
    first  = p.first;
    second = p.second;
    return *this;
  }

  std::pair<T1, T2> to_std_pair() const {
    return std::make_pair(first, second);
  }
};

template <class T1, class T2>
struct pair<T1, T2&> {
  using first_type = T1;
  using second_type = T2&;

  first_type first;
  second_type second;

  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(first_type const& f, second_type s)
      : first(f), second(s) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const pair<U, V>& p)
      : first(p.first), second(p.second) {}

  // from std::pair<U,V>
  template <class U, class V>
  pair(const std::pair<U, V>& p) : first(p.first), second(p.second) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION pair<first_type, second_type>& operator=(
      const pair<U, V>& p) {
    first  = p.first;
    second = p.second;
    return *this;
  }

  std::pair<T1, T2> to_std_pair() const {
    return std::make_pair(first, second);
  }
};

template <class T1, class T2>
struct pair<T1&, T2> {
  using first_type = T1&;
  using second_type = T2;

  first_type first;
  second_type second;

  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(first_type f, second_type const& s)
      : first(f), second(s) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const pair<U, V>& p)
      : first(p.first), second(p.second) {}

  // from std::pair<U,V>
  template <class U, class V>
  pair(const std::pair<U, V>& p) : first(p.first), second(p.second) {}

  template <class U, class V>
  KOKKOS_FORCEINLINE_FUNCTION pair<first_type, second_type>& operator=(
      const pair<U, V>& p) {
    first  = p.first;
    second = p.second;
    return *this;
  }

  std::pair<T1, T2> to_std_pair() const {
    return std::make_pair(first, second);
  }
};

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator==(const pair<T1, T2>& lhs,
                                                      const pair<T1, T2>& rhs) {
  return lhs.first == rhs.first && lhs.second == rhs.second;
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator!=(const pair<T1, T2>& lhs,
                                                      const pair<T1, T2>& rhs) {
  return !(lhs == rhs);
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator<(const pair<T1, T2>& lhs,
                                                     const pair<T1, T2>& rhs) {
  return lhs.first < rhs.first ||
         (!(rhs.first < lhs.first) && lhs.second < rhs.second);
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator<=(const pair<T1, T2>& lhs,
                                                      const pair<T1, T2>& rhs) {
  return !(rhs < lhs);
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator>(const pair<T1, T2>& lhs,
                                                     const pair<T1, T2>& rhs) {
  return rhs < lhs;
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator>=(const pair<T1, T2>& lhs,
                                                      const pair<T1, T2>& rhs) {
  return !(lhs < rhs);
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION constexpr pair<T1, T2> make_pair(T1 x, T2 y) {
  return (pair<T1, T2>(x, y));
}

template <class T1, class T2>
KOKKOS_FORCEINLINE_FUNCTION pair<T1&, T2&> tie(T1& x, T2& y) {
  return (pair<T1&, T2&>(x, y));
}

//
// Specialization of Kokkos::pair for a \c void second argument.  This
// is not actually a "pair"; it only contains one element, the first.
//
template <class T1>
struct pair<T1, void> {
  using first_type  = T1;
  using second_type = void;

  first_type first;
  enum { second = 0 };

  KOKKOS_DEFAULTED_FUNCTION constexpr pair() = default;

  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const first_type& f) : first(f) {}

  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const first_type& f, int)
      : first(f) {}

  template <class U>
  KOKKOS_FORCEINLINE_FUNCTION constexpr pair(const pair<U, void>& p)
      : first(p.first) {}

  template <class U>
  KOKKOS_FORCEINLINE_FUNCTION pair<T1, void>& operator=(
      const pair<U, void>& p) {
    first = p.first;
    return *this;
  }
};

//
// Specialization of relational operators for Kokkos::pair<T1,void>.
//

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator==(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return lhs.first == rhs.first;
}

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator!=(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return !(lhs == rhs);
}

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator<(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return lhs.first < rhs.first;
}

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator<=(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return !(rhs < lhs);
}

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator>(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return rhs < lhs;
}

template <class T1>
KOKKOS_FORCEINLINE_FUNCTION constexpr bool operator>=(
    const pair<T1, void>& lhs, const pair<T1, void>& rhs) {
  return !(lhs < rhs);
}

namespace Impl {

template <class T>
struct is_pair_like : std::false_type {};
template <class T, class U>
struct is_pair_like<Kokkos::pair<T, U>> : std::true_type {};
template <class T, class U>
struct is_pair_like<std::pair<T, U>> : std::true_type {};

}  // end namespace Impl

}  // namespace Kokkos

#ifdef KOKKOS_IMPL_PUBLIC_INCLUDE_NOTDEFINED_PAIR
#undef KOKKOS_IMPL_PUBLIC_INCLUDE
#undef KOKKOS_IMPL_PUBLIC_INCLUDE_NOTDEFINED_PAIR
#endif
#endif  // KOKKOS_PAIR_HPP