Do Understanding and Generation Fight? A Diagnostic Study of DPO for Unified Multimodal Models
Unified multimodal models share a language model backbone for both understanding and generating images. Can DPO align both capabilities simultaneously? We present the first systematic study of this question, applying DPO to Janus-Pro at 1B and 7B parameters under seven training strategies and two post-hoc methods. The central finding is negative: generation quality resists DPO alignment across all tested conditions on this architecture. No method improves generation CLIPScore at 7B (|Delta| < 0.2, p > 0.5 at n=200 per seed, 3 seeds); at 1B, all methods degrade generation, and the result holds across preference data types (real-vs-generated and model-vs-model) and the data volumes tested (...
| Authors | Abinav Rao, Sujan Rachuri |
|---|---|
| Primary category | cs.LG |
| Published | 17 March 2026 |
| Last updated at source | 22 May 2026 |
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