Alpaka: Unit Test atomic can not be compiled with CUDA

[psychocoderHPC]

The test case is not compiling if CUDA is available

$ cmake alpaka/test/unit/atomic/
$ make
[ 20%] Building CXX object CMakeFiles/common.dir/alpaka/test/common/src/Dummy.cpp.o
[ 40%] Linking CXX static library libcommon.a
[ 40%] Built target common
[ 80%] Building NVCC (Device) object CMakeFiles/atomic.dir/src/atomic_generated_AtomicTest.cpp.o
[ 80%] Building NVCC (Device) object CMakeFiles/atomic.dir/src/atomic_generated_main.cpp.o
alpaka/include/alpaka/atomic/AtomicCudaBuiltIn.hpp(108) Error: unsupported operation

CMake Error at atomic_generated_AtomicTest.cpp.o.cmake:279 (message):
  Error generating file
  /bigdata/hplsim/scratch/widera/buildAlpaka/CMakeFiles/atomic.dir/src/./atomic_generated_AtomicTest.cpp.o

module li
Currently Loaded Modulefiles:
  1) gcc/5.3.0              4) cuda/8.0               7) pngwriter/0.7.0
  2) cmake/3.10.1           5) openmpi/2.1.2.cuda80   8) hdf5-parallel/1.8.20
  3) boost/1.62.0           6) zlib/1.2.8             9) libsplash/1.7.0

[BenjaminW3]

This test has some special casing for CUDA. The other accelerators support many different primitive types for atomic operations, but CUDA should be checked only for std::uint32_t. At least this is what I intended with the code in AtomicTest.cpp.

[BenjaminW3]

I am currently investigating this issue and found a first mistake. The test is only executed with std::int32_t in CI but it is only enabled for CUDA when std::uint32_t is selected. So compilation of the atomic test had been disabled for CUDA in the CI...

[BenjaminW3]

I have done some tests in CI and for now I can say that the error is limited to sm_20 which is only available in CUDA 8.0. I will try to figure out more.

[BenjaminW3]

It seems to be a nvcc problem. Clang with CUDA 8.0 and sm_20 works.

[BenjaminW3]

Hmm... It is not even related to sm_20. It does not work with sm_30 or sm_35 either. Furthermore, it does not seem to be related to atomicAdd. Other atomic operations (e.g. atomicMin) do also fail.

[BenjaminW3]

It fails with gcc 4.9 as well as gcc 5.0 in release and in debug builds.

[BenjaminW3]

Ah... It may be related to the usage of local variables as target of the atomic operation. Atomics on registers do not seem to be supported by nvcc 8.0. I will try to fix this.

[BenjaminW3]

My test is green now. I will provide a fixed test.