Function get_update_function_2_moment

include/core/optimizer.h:262–269

 */
template<class Float, OptimizerType optimizer_type>
__host__ __device__ decltype(&Optimizer::adam_update<Float>) get_update_function_2_moment() {
    switch (optimizer_type) {
        case kAdam:
            return &Optimizer::adam_update<Float>;
        default:
            return nullptr;
    }
}

/** Helper class for SGD */
class SGD : public Optimizer {