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Apple Machine Learning Research1 min readpaperadvanced

Trajectory as the Teacher: Few-Step Discrete Flow Matching via Energy-Navigated Distillation

Summary

Apple researchers propose Trajectory‑Shaped Discrete Flow Matching (TS‑DFM), a training‑time distillation method that replaces blind stochastic jumps in discrete flow‑matching with an energy‑based compass to select higher‑quality intermediate tokens. On a 170 M‑parameter language model, the 8‑step student outperforms the 1 024‑step teacher by 32 % perplexity while being 128× faster, beating basel…

  • In discrete flow‑matching, the teacher’s multi‑step trajectory can be the bottleneck because early poor decisions propagate forward.
  • TS‑DFM introduces a lightweight energy evaluator at each intermediate step during training, guiding the trajectory toward more coherent continuations without affecting inference cost.
  • Empirical results on a 170 M‑parameter LM show the shaped student (8 steps) achieves 32 % lower perplexity than the 1 024‑step teacher and runs 128× faster.
  • Performance gains hold across different source data distributions and three evaluator scales, surpassing baselines trained on significantly more data or larger models.

The work reframes the limiting factor in discrete flow‑matching from model capacity to trajectory quality, offering a practical way to compress many‑step generative processes into a few steps without sacrificing output quality. This could make discrete diffusion‑style language models viable for lat…

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