MuFi modeling is used to optimally combine the previously mentioned LoFi and HiFi methods. This is done by GPR, which predicts posterior, i.e. not yet known data (in the following marked by an asterisk) for test points based on prior, i.e. known data n. The probability p that the model takes the function value f * at unknown positions x x x * when already data pairs y y y n , x x x n are known is then computed from a multivariate Gaussian distribution.