Non-Normal Diffusion Models
This work addresses a foundational limitation in diffusion models for machine learning researchers, offering incremental improvements by expanding design choices.
The authors tackled the problem of limited flexibility in diffusion models by generalizing the framework to allow non-normal distributions for diffusion steps, which expanded the class of diffusion processes and enabled greater flexibility in loss functions during training. They demonstrated effectiveness on density estimation and generative modeling tasks with standard image datasets, showing that different distributions produce qualitatively different generated samples.
Diffusion models generate samples by incrementally reversing a process that turns data into noise. We show that when the step size goes to zero, the reversed process is invariant to the distribution of these increments. This reveals a previously unconsidered parameter in the design of diffusion models: the distribution of the diffusion step $Δx_k := x_{k} - x_{k + 1}$. This parameter is implicitly set by default to be normally distributed in most diffusion models. By lifting this assumption, we generalize the framework for designing diffusion models and establish an expanded class of diffusion processes with greater flexibility in the choice of loss function used during training. We demonstrate the effectiveness of these models on density estimation and generative modeling tasks on standard image datasets, and show that different choices of the distribution of $Δx_k$ result in qualitatively different generated samples.