MCMC-Correction of Score-Based Diffusion Models for Model Composition
While energy-parameterized diffusion models support Metropolis-Hastings (MH)-based MCMC sampling—yielding substantially improved sample quality under model composition—standard score-parameterized models lack an explicit energy function, preventing direct MH correction. Method: We propose Score-MCMC, a framework that reconstructs energy differences via line-integral approximations of the pre-trained score function, enabling derivation of a computable MH acceptance probability without modifying the underlying score model. Contribution/Results: Score-MCMC theoretically and practically bridges score-based and energy-based MCMC sampling. By coupling the diffusion reverse process with MH correction, it achieves sampling fidelity and diversity on par with energy-parameterized models across multiple benchmarks—particularly enhancing compositional distribution modeling in terms of both accuracy and sample diversity.