Support oneAPI SYCL

examples/alpaka/nbody/nbody.cpp

@@ -27,15 +27,25 @@ constexpr auto steps = 5; ///< number of steps to calculate
 constexpr auto allowRsqrt = true; // rsqrt can be way faster, but less accurate
 constexpr auto runUpate = true; // run update step. Useful to disable for benchmarking the move step.
 
-#if defined(ALPAKA_ACC_CPU_B_SEQ_T_SEQ_ENABLED) || defined(ALPAKA_ACC_CPU_B_OMP2_T_SEQ_ENABLED)
-#    if defined(ALPAKA_ACC_GPU_CUDA_ENABLED) || defined(ALPAKA_ACC_GPU_HIP_ENABLED)
-#        error Cannot enable CUDA together with other backends
-#    endif
+#if defined(ALPAKA_ACC_CPU_B_SEQ_T_SEQ_ENABLED) || defined(ALPAKA_ACC_CPU_B_OMP2_T_SEQ_ENABLED)                       \
+    || (defined(ALPAKA_ACC_SYCL_ENABLED) && defined(ALPAKA_SYCL_ONEAPI_CPU))
+#    define ANY_CPU_ENABLED 1
+#endif
+#if defined(ALPAKA_ACC_GPU_CUDA_ENABLED) || defined(ALPAKA_ACC_GPU_HIP_ENABLED)                                       \
+    || (defined(ALPAKA_ACC_SYCL_ENABLED) && defined(ALPAKA_SYCL_ONEAPI_GPU))
+#    define ANY_GPU_ENABLED 1
+#endif
+
+#if ANY_CPU_ENABLED && ANY_GPU_ENABLED
+#    error Cannot enable CPU and GPU backends at the same time
+#endif
+
+#if ANY_CPU_ENABLED
 constexpr auto elementsPerThread = xsimd::batch<float>::size;
 constexpr auto threadsPerBlock = 1;
 constexpr auto sharedElementsPerBlock = 1;
 constexpr auto aosoaLanes = xsimd::batch<float>::size; // vectors
-#elif defined(ALPAKA_ACC_GPU_CUDA_ENABLED) || defined(ALPAKA_ACC_GPU_HIP_ENABLED)
+#elif ANY_GPU_ENABLED
 constexpr auto threadsPerBlock = 256;
 constexpr auto sharedElementsPerBlock = 512;
 constexpr auto elementsPerThread = 1;