implement AccIsEnabled

- the value of AccIsEnabled indicates whether an accelerator is enabled for a specific tag

include/alpaka/acc/Tag.hpp

@@ -5,6 +5,7 @@
 #pragma once
 
 #include "alpaka/core/BoostPredef.hpp"
+#include "alpaka/dim/DimIntegralConst.hpp"
 
 #include <iostream>
 #include <type_traits>
@@ -56,3 +57,32 @@ namespace alpaka
     template<typename TAcc, typename... TTag>
     inline constexpr bool accMatchesTags = (std::is_same_v<alpaka::AccToTag<TAcc>, TTag> || ...);
 } // namespace alpaka
+
+// include all Acc's because of the struct AccIsEnabled
+// if an acc is not include, it will be not enabled independent of the compiler flags
+// include after defining the traits alpaka::AccToTag and alpaka::TagToAcc because it
+// is a circular dependency
+#include "alpaka/acc/AccCpuOmp2Blocks.hpp"
+#include "alpaka/acc/AccCpuOmp2Threads.hpp"
+#include "alpaka/acc/AccCpuSerial.hpp"
+#include "alpaka/acc/AccCpuSycl.hpp"
+#include "alpaka/acc/AccCpuTbbBlocks.hpp"
+#include "alpaka/acc/AccCpuThreads.hpp"
+#include "alpaka/acc/AccFpgaSyclIntel.hpp"
+#include "alpaka/acc/AccGpuCudaRt.hpp"
+#include "alpaka/acc/AccGpuHipRt.hpp"
+
+namespace alpaka
+{
+    /// @brief check if the accelerator is enabled for a given tag
+    /// @tparam TTag alpaka tag type
+    template<typename TTag, typename = void>
+    struct AccIsEnabled : std::false_type
+    {
+    };
+
+    template<typename TTag>
+    struct AccIsEnabled<TTag, std::void_t<TagToAcc<TTag, alpaka::DimInt<1>, int>>> : std::true_type
+    {
+    };
+} // namespace alpaka

test/unit/acc/src/AccTagTest.cpp

@@ -248,3 +248,19 @@ TEMPLATE_LIST_TEST_CASE("kernel specialization with tags", "[acc][tag]", TestAcc
 
     REQUIRE(alpaka::getPtrNative(memHost)[0] == expected_result);
 }
+
+TEMPLATE_LIST_TEST_CASE("test AccIsEnabled", "[acc][tag]", AccToTagMap)
+{
+    using TestAcc = std::tuple_element_t<0, TestType>;
+    using TestTag = std::tuple_element_t<1, TestType>;
+
+    // if the Acc is not enabled, the type is int
+    if constexpr(!std::is_same_v<TestAcc, int>)
+    {
+        STATIC_REQUIRE(alpaka::AccIsEnabled<TestTag>::value);
+    }
+    else
+    {
+        STATIC_REQUIRE_FALSE(alpaka::AccIsEnabled<TestTag>::value);
+    }
+}