Method exp

dnn/include/megdnn/dtype/half.hpp:1193–1199

			/// \param arg function argument
			/// \return function value stored in single-preicision
            MEGDNN_HOST MEGDNN_DEVICE static expr exp(float arg) {
#if defined(__CUDA_ARCH__)
                return expr(expf(arg));
#else
                return expr(std::exp(arg));
#endif
            }

			/// Exponential implementation.
			/// \param arg function argument