“…A recent work proposed by (Khan, Kani, & Elsheikh, 2019) focused on machine learning based hybrid multilevel multifidelity method, which utilizes the POD based approximation and gradient boosted tree surrogate model. Multifidelity methods have much broader applications, not only Monte Carlo based methods, but also more general UQ aspects, for example, optimization with uncertainty (Pang, Perdikaris, Cai, & Karniadakis, 2017;Bonfiglio, Perdikaris, Brizzolara, & Karniadakis, 2018;Heinkenschloss, Kramer, Takhtaganov, & Willcox, 2018), multifidelity surrogate modeling (Perdikaris, Venturi, Royset, & Karniadakis, 2015;Parussini, Venturi, Perdikaris, & Karniadakis, 2017;Giselle Fernández-Godino, Park, Kim, & Haftka, 2019;Guo, Song, Park, Li, & Haftka, 2018;Chaudhuri, Lam, & Willcox, 2018;Tian et al, 2020) and multifidelity information reuse, and fusion (Cook, Jarrett, & Willcox, 2018;Perdikaris, Venturi, & Karniadakis, 2016). We refer to (Park et al, 2017;Peherstorfer, Willcox, & Gunzburger, 2018) for a comprehensive introduction and in-depth discussion of multifidelity methods for uncertainty propagation.…”