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Learning to Generate via Understanding: Understanding-Driven Intrinsic Rewarding for Unified Multimodal Models
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Proposes GvU, a self-supervised GRPO-based RL method where a unified multimodal model (X-Omni) uses its own understanding branch's token-level text-image likelihood as an intrinsic reward to improve text-to-image generation.
Problem
Unified multimodal models understand images better than they generate them; the understanding-generation gap limits T2I quality, and existing rewards are coarse or prone to hacking.
Approach
Use the UMM's own understanding branch to compute the geometric-mean token probability of the ground-truth prompt given the generated image, and use this token-level intrinsic likelihood as the GRPO reward, with no external reward model or image data.
Key results
- GenEval overall improves from 0.68 to 0.81 without LLM rewriting (0.84 with rewriter) after GvU RL.
- GenEval++ overall rises from 0.282 to 0.404 (43.3% relative gain), the top score in its comparison table.
- DPG-Bench overall reaches 85.68, the best among compared models; on MMT-Bench overall the base improves from 49.76 to 49.92, with larger gains on fine-grained subtasks such as VI (+5.06).
Surprising findings
- Training from a weaker base model yields a much larger relative gain on GenEval (+138.1% vs +19.1% for the regular base), suggesting a larger understanding-generation gap helps.
- Gains on understanding benchmarks are modest, and the method is trained without any image-understanding supervision yet still improves some fine-grained MMT-Bench subtasks.
Limitations
- Understanding gains are relatively modest.
- Results reported primarily on a single base model (X-Omni) with a self-built RL framework.
- Reward is a likelihood proxy; sensitivity analysis is only qualitative on prompt-term removal.
Experimental setup
Datasets: self-generated text prompt dataset (50,000 samples)
Benchmarks: GenEval DPG-Bench GenEval++ POPE GQA MMBench SEED DocVQA OCRBench MMT-Bench
Metrics: overall score accuracy
Baselines: SD3-medium FLUX.1-dev BAGEL Janus-Pro OmniGen2 XOmni GPT-4o BLIP3-o 8B UniWorld-V1
Builds on: GRPO X-Omni TRL LoRA
Closest papers by meaning
- Generation Enhances Understanding in Unified Multimodal Models via Multi-Representation Generation (ICML 2026 · similarity 0.90)
- Towards Unified Multimodal Interleaved Generation via Group Relative Policy Optimization (NeurIPS 2025 · similarity 0.90)
- Janus-Pro-R1: Advancing Collaborative Visual Comprehension and Generation via Reinforcement Learning (NeurIPS 2025 · similarity 0.90)
- DuoGen: Towards Autonomous Interleaved Multimodal Generation (CVPR 2026 · similarity 0.90)
- Vision as a Dialect: Unifying Visual Understanding and Generation via Text-Aligned Representations (NeurIPS 2025 · similarity 0.89)
- Janus: Decoupling Visual Encoding for Unified Multimodal Understanding and Generation (CVPR 2025 · similarity 0.89)
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