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Enable zip_iterator to satisfy C++20 std::input_iterator constraint #1408

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merged 16 commits into from
Apr 30, 2024
Merged

Enable zip_iterator to satisfy C++20 std::input_iterator constraint #1408

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b2ff3d4
Specialize std::basic_common_reference for std::tuple and oneapi::dpl…
mmichel11 Feb 13, 2024
118c5c8
Add comments to motivate basic_common_reference specializations
mmichel11 Feb 14, 2024
8512e47
Use _ONEDPL___cplusplus macro to detect cpp version
mmichel11 Feb 14, 2024
d47996b
Switch to using oneapi::dpl::__internal::tuple in zip_forward_iterator
mmichel11 Feb 20, 2024
854ca16
Remove non-compliant basic_common_reference for std::tuple
mmichel11 Feb 20, 2024
5e8ae8d
Keep ::std::tuple wrapper for pointer type in zip_forward_iterator
mmichel11 Feb 23, 2024
f95ae0b
Add macro for library concepts support
mmichel11 Apr 2, 2024
643a34a
Correct _LIBCPP_VERSION check
mmichel11 Apr 2, 2024
df72987
Use oneapi::dpl::__internal::tuple everywhere in zip_forward_iterator
mmichel11 Apr 3, 2024
df1344e
Only use oneapi::dpl::__internal::tuple in zip_forward_iterator with
mmichel11 Apr 16, 2024
0e2b946
Clarify comment on std::tuple and proxy references
mmichel11 Apr 17, 2024
1836d57
Adjust how we define oneDPL macros dependent on STD feature macros
mmichel11 Apr 17, 2024
c9df306
Fix lines that broke CMake parsing of onedpl_config.h
mmichel11 Apr 17, 2024
134416e
Add clarifying comment on basic_common_reference concepts dependency …
mmichel11 Apr 17, 2024
7686e3e
Add comment to remind developers to keep zip_forward_iterator internal
mmichel11 Apr 29, 2024
bb05e9b
Address comment suggestions for zip_forward_iterator
mmichel11 Apr 29, 2024
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18 changes: 13 additions & 5 deletions include/oneapi/dpl/pstl/iterator_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -79,18 +79,26 @@ struct __make_references
template <typename... _Types>
class zip_forward_iterator
{
template <typename... _Ts>
using __tuple_t =
#if _ONEDPL_CAN_USE_STD_TUPLE_PROXY_ITERATOR
::std::tuple<_Ts...>;
#else
oneapi::dpl::__internal::tuple<_Ts...>;
#endif

static const ::std::size_t __num_types = sizeof...(_Types);
typedef typename ::std::tuple<_Types...> __it_types;
typedef __tuple_t<_Types...> __it_types;
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public:
typedef ::std::make_signed_t<::std::size_t> difference_type;
typedef ::std::tuple<typename ::std::iterator_traits<_Types>::value_type...> value_type;
typedef ::std::tuple<typename ::std::iterator_traits<_Types>::reference...> reference;
typedef ::std::tuple<typename ::std::iterator_traits<_Types>::pointer...> pointer;
typedef __tuple_t<typename ::std::iterator_traits<_Types>::value_type...> value_type;
typedef __tuple_t<typename ::std::iterator_traits<_Types>::reference...> reference;
typedef __tuple_t<typename ::std::iterator_traits<_Types>::pointer...> pointer;
typedef ::std::forward_iterator_tag iterator_category;

zip_forward_iterator() : __my_it_() {}
explicit zip_forward_iterator(_Types... __args) : __my_it_(::std::make_tuple(__args...)) {}
explicit zip_forward_iterator(_Types... __args) : __my_it_(__tuple_t<_Types...>{__args...}) {}

reference operator*() const
{
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28 changes: 28 additions & 0 deletions include/oneapi/dpl/pstl/onedpl_config.h
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Expand Up @@ -16,6 +16,10 @@
#ifndef _ONEDPL_CONFIG_H
#define _ONEDPL_CONFIG_H

#if _ONEDPL___cplusplus >= 202002L && __has_include(<version>)
# include <version>
#endif

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#ifndef _PSTL_VERSION
# define _PSTL_VERSION 11000
# define _PSTL_VERSION_MAJOR (_PSTL_VERSION / 1000)
Expand Down Expand Up @@ -296,6 +300,30 @@
#define _ONEDPL_CPP20_SHIFT_LEFT_RIGHT_PRESENT \
(_ONEDPL___cplusplus >= 202002L && (_MSC_VER >= 1921 || _GLIBCXX_RELEASE >= 10))

#if _ONEDPL___cplusplus >= 202002L && __cpp_concepts >= 201907L && __cpp_lib_concepts >= 202002L
# define _ONEDPL_CPP20_CONCEPTS_PRESENT 1
#else
# define _ONEDPL_CPP20_CONCEPTS_PRESENT 0
#endif

#if _ONEDPL___cplusplus >= 202302L && __cpp_lib_tuple_like >= 202207L
# define _ONEDPL_CPP23_TUPLE_LIKE_COMMON_REFERENCE_PRESENT 1
#else
# define _ONEDPL_CPP23_TUPLE_LIKE_COMMON_REFERENCE_PRESENT 0
#endif

#if _ONEDPL___cplusplus >= 202302L && __cpp_lib_ranges_zip >= 202110L
# define _ONEDPL_CPP23_RANGES_ZIP_PRESENT 1
#else
# define _ONEDPL_CPP23_RANGES_ZIP_PRESENT 0
#endif
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// To use std::tuple as a proxy reference and satisfy iterator concepts for C++20 and beyond, we need
// the changes to std::tuple in P2321R2 and the tuple-like basic_common_reference specialization in P2165R4.
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#define _ONEDPL_CAN_USE_STD_TUPLE_PROXY_ITERATOR \
(!_ONEDPL_CPP20_CONCEPTS_PRESENT || \
(_ONEDPL_CPP23_RANGES_ZIP_PRESENT && _ONEDPL_CPP23_TUPLE_LIKE_COMMON_REFERENCE_PRESENT))

#define _ONEDPL_BUILT_IN_STABLE_NAME_PRESENT __has_builtin(__builtin_sycl_unique_stable_name)

#if defined(_MSC_VER) && __INTEL_LLVM_COMPILER < 20240100
Expand Down
12 changes: 12 additions & 0 deletions include/oneapi/dpl/pstl/tuple_impl.h
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Expand Up @@ -669,6 +669,18 @@ get(const oneapi::dpl::__internal::tuple<_Tp...>&& __a)
{
return ::std::move(__a).template get<_Idx>();
}

// To enable oneapi::dpl::zip_iterator to satisfy the requirements for the std::input_iterator concept in C++20,
// we must provide a basic_common_reference specialization for our internal tuple implementation.
#if _ONEDPL_CPP20_CONCEPTS_PRESENT
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template <typename... TTypes, typename... UTypes, template <typename> typename TQual,
template <typename> typename UQual>
struct basic_common_reference<oneapi::dpl::__internal::tuple<TTypes...>, oneapi::dpl::__internal::tuple<UTypes...>,
TQual, UQual>
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I'm having trouble understanding TQual and UQual.

Are they just something which is required for this function for it to be of use to the Standard library implementation?
Perhaps it uses these to add type qualifiers like const to the types?

Its not very clear to me as it is written in the standard.

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They are required for this function to be used by the standard library implementation. My understanding is that they add cvref-qualifiers to the types.

It is mentioned briefly in the explanation of std::common_reference's required behavior:

"Otherwise, if std::basic_common_reference<std::remove_cvref_t<T1>, std::remove_cvref_t<T2>, T1Q, T2Q>::type exists, where TiQ is a unary alias template such that TiQ is U with the addition of Ti's cv- and reference qualifiers, then the member type type names that type;"

{
using type = oneapi::dpl::__internal::tuple<::std::common_reference_t<TQual<TTypes>, UQual<UTypes>>...>;
};
#endif
} // namespace std

#endif // _ONEDPL_TUPLE_IMPL_H
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