[oneDPL][ranges][L1] + ranges __pattern_reverse

Author: MikeDvorskiy

include/oneapi/dpl/pstl/algorithm_ranges_impl.h

@@ -748,7 +748,7 @@ __pattern_unique(_Tag __tag, _ExecutionPolicy&& __exec, _R&& __r, _Comp __comp,
     auto __it = oneapi::dpl::__internal::__pattern_unique(__tag, std::forward<_ExecutionPolicy>(__exec),
                                                           __beg, __end, __pred_2);
 
-    return std::ranges::borrowed_subrange_t<_R>(__it, __end);
+    return {__it, __end};
 }
 
 template <typename _Tag, typename _ExecutionPolicy, typename _R, typename _Comp, typename _Proj>
@@ -758,6 +758,27 @@ __pattern_unique(__serial_tag</*IsVector*/ std::false_type>, _ExecutionPolicy&&,
     return std::ranges::unique(std::forward<_R>(__r), __comp, __proj);
 }
 
+template <typename _Tag, typename _ExecutionPolicy, typename _R>
+std::ranges::borrowed_subrange_t<_R>
+__pattern_reverse(_Tag __tag, _ExecutionPolicy&& __exec, _R&& __r)
+{
+    auto __beg = std::ranges::begin(__r);
+    const auto __n = std::ranges::size(__r);
+    const auto __n_2 = __n / 2;
+    auto __r1 = std::ranges::take_view(__r, __n_2);
+    auto __r2 = std::ranges::take_view(std::ranges::reverse_view(__r), __n_2);
+
+    __pattern_swap_ranges(std::forward<_ExecutionPolicy>(__exec), std::move(__r1), std::move(__r2))
+    return {__beg + __n};
+}
+
+template <typename _Tag, typename _ExecutionPolicy, typename _R>
+std::ranges::borrowed_subrange_t<_R>
+__pattern_reverse(__serial_tag</*IsVector*/ std::false_type>, _ExecutionPolicy&&, _R&& __r)
+{
+    return std::ranges::reverse(std::forward<_R>(__r));
+}
+
 template <typename _Tag, typename _ExecutionPolicy, typename _R, typename _OutRange, typename _Comp, typename _Proj>
 std::ranges::unique_copy_result<std::ranges::borrowed_iterator_t<_R>, std::ranges::borrowed_iterator_t<_OutRange>>
 __pattern_unique_copy(_Tag __tag, _ExecutionPolicy&& __exec, _R&& __r, _OutRange&& __out_r, _Comp __comp, _Proj __proj)

include/oneapi/dpl/pstl/glue_algorithm_ranges_impl.h

@@ -1124,6 +1124,10 @@ struct __reverse_fn
 
         oneapi::dpl::ranges::swap_ranges(std::forward<_ExecutionPolicy>(__exec), std::move(__r1),std::move(__r2));
         return {std::ranges::begin(__r) + __n};
+        
+        const auto __dispatch_tag = oneapi::dpl::__ranges::__select_backend(__exec);
+        return oneapi::dpl::__internal::__ranges::__pattern_reverse(__dispatch_tag,
+            std::forward<_ExecutionPolicy>(__exec), std::forward<_R>(__r));
     }
 
 }; //__reverse_fn

include/oneapi/dpl/pstl/hetero/algorithm_ranges_impl_hetero.h

@@ -791,6 +791,19 @@ __pattern_unique_copy(__hetero_tag<_BackendTag> __tag, _ExecutionPolicy&& __exec
 
     return {__end, __beg_out + __idx};
 }
+
+template <typename _BackendTag, typename _ExecutionPolicy, typename _R>
+std::ranges::borrowed_iterator_t<_R>
+__pattern_reverse(__hetero_tag<_BackendTag> __tag, _ExecutionPolicy&& __exec, _R&& __r)
+{
+    auto __beg = std::ranges::begin(__r);
+
+    auto __i = oneapi::dpl::__par_backend_hetero::__parallel_for(_BackendTag{}, std::forward<_ExecutionPolicy>(__exec),
+        unseq_backend::__reverse_functor<typename std::iterator_traits<_Iterator>::difference_type>{__n}, __n / 2,
+        oneapi::dpl::__ranges::views::all(std::forward<_R>(__r))).__checked_deferrable_wait();
+
+    return {__beg + __i};
+}
 #endif //_ONEDPL_CPP20_RANGES_PRESENT
 
 //------------------------------------------------------------------------