Add Stacked accessor

alpaka-group · Aug 1, 2023 · d65fee7 · d65fee7
1 parent 6564102
commit d65fee7
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diff --git a/docs/pages/api.rst b/docs/pages/api.rst
@@ -177,6 +177,7 @@ Acessors
 .. doxygenstruct:: llama::accessor::Const
 .. doxygenstruct:: llama::accessor::Restrict
 .. doxygenstruct:: llama::accessor::Atomic
+.. doxygenstruct:: llama::accessor::Stacked
 
 RecordDim flattener
 ^^^^^^^^^^^^^^^^^^^

diff --git a/include/llama/Accessors.hpp b/include/llama/Accessors.hpp
@@ -111,4 +111,42 @@ namespace llama::accessor
         }
     };
 #endif
+
+    namespace internal
+    {
+        template<std::size_t I, typename Accessor>
+        struct StackedLeave : Accessor
+        {
+        };
+    } // namespace internal
+
+    /// Accessor combining multiple other accessors. The contained accessors are applied in left to right order to the
+    /// memory location when forming the reference returned from a view.
+    template<typename... Accessors>
+    struct Stacked : internal::StackedLeave<0, Default>
+    {
+    };
+
+    template<typename FirstAccessor, typename... MoreAccessors>
+    struct Stacked<FirstAccessor, MoreAccessors...>
+        : internal::StackedLeave<1 + sizeof...(MoreAccessors), FirstAccessor>
+        , Stacked<MoreAccessors...>
+    {
+        using First = internal::StackedLeave<1 + sizeof...(MoreAccessors), FirstAccessor>;
+        using Rest = Stacked<MoreAccessors...>;
+
+        LLAMA_FN_HOST_ACC_INLINE Stacked() = default;
+
+        LLAMA_FN_HOST_ACC_INLINE explicit Stacked(FirstAccessor first, MoreAccessors... rest)
+            : First{std::move(first)}
+            , Rest{std::move(rest)...}
+        {
+        }
+
+        template<typename Reference>
+        LLAMA_FN_HOST_ACC_INLINE auto operator()(Reference&& r) const -> decltype(auto)
+        {
+            return static_cast<const Rest&>(*this)(static_cast<const First&>(*this)(std::forward<Reference>(r)));
+        }
+    };
 } // namespace llama::accessor
diff --git a/tests/accessor.cpp b/tests/accessor.cpp
@@ -160,3 +160,15 @@ TEST_CASE("view.withAccessor.OffsetFloatAccessor")
     CHECK(view2(0)(tag::Pos{})(tag::X{}) == 2.0);
     CHECK(view2(0)(tag::Mass{}) == 12.0f);
 }
+
+TEST_CASE("view.allocView.Stacked")
+{
+    auto mapping = llama::mapping::AoS{llama::ArrayExtents{3, 4}, Particle{}};
+
+    auto view = llama::allocView(
+        mapping,
+        llama::bloballoc::Vector{},
+        llama::accessor::Stacked<llama::accessor::Default, llama::accessor::Restrict, llama::accessor::Default>{});
+    iotaFillView(view);
+    iotaCheckView(view);
+}