There is a stochastic element to diffusion models which is not present in PFGMs. Further, recall that Diffusion Models and PFGMs alike are "metamodels" - mathem

There is a stochastic element to diffusion models which is not present in PFGMs. Further, recall that Diffusion Models and PFGMs alike are "metamodels" - mathematical frameworks in which any function approximator can, in theory, be placed. They are not an architecture. In this case, the authors use the DDPM++ backbone which is the specific function approximator that they implement in their PFGM framework.