研究强化学习后训练中计算资源如何分配,提升模型效率。
Where Should RL Post-Training Compute Go? Model Size, Search, Learning, and Feedback

- 提出FLOP分解框架,区分策略更新、搜索、反馈评估的计算开销。
- 相同预算下,大模型需更少训练轮次,小模型可更长时间训练。
- 适合关注推理优化与资源分配的研究者,尤其在机器人学习场景。
强化学习(RL)后训练被广泛用于适配基础模型以实现推理、规划和反馈驱动的机器人学习流程,但受限的后训练资源通常仅以总浮点运算量(FLOP)预算来概括。本文研究这一实践背后的固定预算决策问题:在相同后训练预算下,应选择更大规模的策略模型、延长小模型的训练时间、生成更多轨迹搜索,还是投入更多算力于更强的奖励反馈?我们引入一个针对GRPO后训练的FLOP会计框架,将计算量分解为轨迹/搜索、策略更新/学习以及奖励或反馈模型评估三部分。在基于LoRA适配的Qwen2.5模型上,发现条件性分配前沿:最佳分配方案随模型规模、预算大小、奖励系统及评估目标而变化。相同FLOP条件下,模型规模与训练分配相互耦合,因大模型每标记消耗更多计算,导致在相同预算下获得更少更新或轨迹。奖励系统也影响分配结构:规则型奖励几乎将所有非更新计算用于策略轨迹生成,而PRM类反馈则明显将部分预算分配给奖励模型推理。我们提出RACE作为诊断性网格协议,用于在昂贵验证前识别分配范式;结果表明,未来RL后训练论文应报告总FLOPs及各类计算的分配比例。
原文摘要 · Abstract (English)
Reinforcement Learning (RL) post-training is increasingly used to adapt foundation models for reasoning, planning, and feedback-driven robot-learning pipelines, but constrained post-training resources are often summarized by a single total FLOP budget. We study the fixed-budget decision problem behind this practice: under the same post-training budget, should one use a larger policy, train a smaller policy longer, generate more rollout search, or spend compute on stronger reward feedback? We introduce a FLOP-accounting framework for GRPO post-training that decomposes compute into rollout/search, policy-update/learning, and reward- or feedback-model evaluation. Across LoRA-adapted Qwen2.5 policies, we find conditional allocation frontiers: the best observed allocation changes with model size, compute budget, reward system, and evaluation target. Same-FLOP model-size comparisons show that model choice and training allocation are coupled because larger policies consume more per-token compute and therefore buy fewer updates or rollouts under the same budget. Reward systems also change the accounting: rule-based rewards spend nearly all non-update compute on policy rollouts, while PRM-style feedback allocates a visible part of the budget to reward-model inference. We present RACE as a diagnostic pilot-grid protocol, not a guarantee of held-out improvement, for identifying allocation regimes before expensive validation runs; our results suggest that RL post-training papers should report total FLOPs together with how compute is divided among model size, search, learning, and feedback.
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