Function impl_sqrt

tensorflow/core/kernels/training_ops_gpu.cu.cc:44–46

// We have no choice but to implement sqrt and rsqrt by hand
template <typename T>
__device__ T impl_sqrt(T x) {
  return sqrt(x);
}
template <typename T>
__device__ T impl_rsqrt(T x) {
  return rsqrt(x);