The hierarchical framework for predicting based on knowledge transfer. (A) The predictive framework utilizes the well-established auxiliary solution, , and the discovered connection to predict . The switchable kernel in this framework, which concretizes the dependence of on , can have multiple versions, i.e., and (Eqs. 6 and 7). (B) These two versions feature different levels of error tolerance, less than 7% and 3% relative error for and , respectively. Note that the original form of in Eq. 5 shows the best approximation capability but does not provide a solid connection between and . The second kernel, , is established with a simple fully connected NN (“2/4/1”), which adds 1.3% relative error.