教普通人设计符合人类偏好的奖励函数,三步搞定。
A Framework for Designing Reward Functions: From Objectives to Features to Human-Aligned Reward Functions

- 把任务目标拆成可测量的变量,形成奖励项基础。
- 用因果图优化选择关键变量,高效求解最优组合。
- 通过交互式反馈精准调权重,保证结果始终合理。
我们提出一个形式化流程,让非专家也能快速构建和迭代符合人类偏好的奖励函数——即遵循特定轨迹偏好排序的奖励函数。给定自然语言描述的任务,该流程分三步生成线性奖励函数:首先将任务目标提炼为基本目标,并推导出可度量的结果变量;其次从结果变量中选出具有因果代表性的子集作为奖励项;最后通过偏好获取拟合各奖励项的权重。本文贡献包括:第一步提供引导式工作流以推导结果变量;第二步将奖励项选择转化为因果有向无环图上的最小代价部分覆盖问题,可通过最大流在多项式时间内求解;第三步将权重拟合建模为几何凸可行性问题,通过偏好查询逐步缩小可行区域,利用现有分离预言机方法求解。据我们所知,这是首个能保持确定无冲突可行权重区域的方法,且仅需 O(n log κ) 次偏好查询即可收敛至指定精度。
原文摘要 · Abstract (English)
We present a formal process to enable non-experts to instantiate and iterate on human-aligned reward functions, i.e. reward functions that adhere to a given preference ordering over trajectories. Given a task described in natural language, our process produces a linear reward function in three steps: distill the task's objectives into a set of fundamental objectives and derive measurable outcome variables that capture those fundamental objectives, select a causally representative subset of outcome variables as the reward terms, and fit weights to those reward terms via preference elicitation. Our contributions describe the first step and formalize the latter two steps. The first is a guided workflow for deriving outcome variables. The second is a reduction of reward term selection to minimum-cost partial cover on a causal DAG, solved in polynomial time via max-flow. The third is a geometric framing of weight fitting as a convex feasibility problem iteratively narrowed by preference queries, solved by existing separation oracle methods. To the best of our knowledge, this is the first reward-design method that maintains a deterministically conflict-free feasible weight region, narrowed to a desired tolerance via a separation oracle with O(n log κ) preference queries.
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