Diffusion Forcing: Next-token Prediction Meets Full-Sequence Diffusion
Authors: name: Boyuan Chen, name: Diego Marti Monso, name: Yilun Du, name: Max Simchowitz, name: Russ Tedrake, name: Vincent Sitzmann

This paper presents Diffusion Forcing, a new training paradigm where a
diffusion model is trained to denoise a set of tokens with independent
per-token noise levels. We apply Diffusion Forcing to sequence generative
modeling by training a causal next-token prediction model to generate one or
several future tokens without fully diffusing past ones. Our approach is shown
to combine the strengths of next-token prediction models, such as
variable-length generation, with the strengths of full-sequence diffusion
models, such as the ability to guide sampling to desirable trajectories. Our
method offers a range of additional capabilities, such as (1) rolling-out
sequences of continuous tokens, such as video, with lengths past the training
horizon, where baselines diverge and (2) new sampling and guiding schemes that
uniquely profit from Diffusion Forcing's variable-horizon and causal
architecture, and which lead to marked performance gains in decision-making and
planning tasks. In addition to its empirical success, our method is proven to
optimize a variational lower bound on the likelihoods of all subsequences of
tokens drawn from the true joint distribution. Project website:
https://boyuan.space/diffusion-forcing/