On Accelerating Diffusion-Based Sampling Process via Improved Integration Approximation
This work accelerates sampling for diffusion models, which is a bottleneck in practical applications like image generation, though it is incremental as it builds on existing ODE-based methods.
The paper tackles the problem of slow sampling in diffusion-based generative models by optimizing coefficients in ODE solvers via improved integration approximation, achieving better FID scores with small computational overhead when neural function evaluations are low (e.g., less than 25).
A popular approach to sample a diffusion-based generative model is to solve an ordinary differential equation (ODE). In existing samplers, the coefficients of the ODE solvers are pre-determined by the ODE formulation, the reverse discrete timesteps, and the employed ODE methods. In this paper, we consider accelerating several popular ODE-based sampling processes (including EDM, DDIM, and DPM-Solver) by optimizing certain coefficients via improved integration approximation (IIA). We propose to minimize, for each time step, a mean squared error (MSE) function with respect to the selected coefficients. The MSE is constructed by applying the original ODE solver for a set of fine-grained timesteps, which in principle provides a more accurate integration approximation in predicting the next diffusion state. The proposed IIA technique does not require any change of a pre-trained model, and only introduces a very small computational overhead for solving a number of quadratic optimization problems. Extensive experiments show that considerably better FID scores can be achieved by using IIA-EDM, IIA-DDIM, and IIA-DPM-Solver than the original counterparts when the neural function evaluation (NFE) is small (i.e., less than 25).