message: Remove atomicAdd
diff: // Define the MFEM inner threading macros
  #if defined(MFEM_USE_CUDA) && defined(__CUDA_ARCH__)
  -#if __CUDA_ARCH__ < 600
  -__device__ double atomicAdd(double* address, double val)
  -{
  - unsigned long long int* address_as_ull =
  - (unsigned long long int*)address;
  - unsigned long long int old = *address_as_ull, assumed;
  -
  - do
  - {
  - assumed = old;
  - old = atomicCAS(address_as_ull, assumed,
  - __double_as_longlong(val +
  - __longlong_as_double(assumed)));
  -
  - // Note: uses integer comparison to avoid hang in case of NaN (since NaN != NaN)
  - }
  - while (assumed != old);
  -
  - return __longlong_as_double(old);
  -}
  -#endif
  #define MFEM_SHARED __shared__
  #define MFEM_SYNC_THREAD __syncthreads()
  #define MFEM_THREAD_ID(k) threadIdx.k
  