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ORSO: Accelerating Reward Design via Online Reward Selection and Policy Optimization
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Proposes ORSO, which treats shaping-reward selection as online model selection (D3RB bandit-style) over LLM-generated reward candidates, trained with PPO on Isaac Gym tasks, to find good shaped rewards within a fixed interaction budget.
Problem
Choosing effective shaping reward functions from a candidate set is computationally expensive because each candidate requires lengthy RL training to evaluate under the task reward.
Approach
Frame shaping-reward selection as an online model selection problem where each candidate reward (with its policy) is a base learner, and allocate training budget with a regret-balancing algorithm (D3RB) so that compute concentrates on promising rewards, with regret guarantees.
Key results
- ORSO achieves 56% higher normalized task reward than naive selection at the highest interaction budget.
- ORSO reaches human-level performance with up to 8x fewer GPUs/less compute than naive selection.
- ORSO's normalized regret can become negative, meaning it finds rewards outperforming human-designed ones on average.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use ORSO instead of naive reward selection at the highest interaction budget | Reward design with PPO · Continuous control tasks, averaged across tasks | normalized task reward: 56% higher | Helped |
| Use ORSO rather than naive selection | Reward design with PPO · Human-level performance across continuous control tasks | number of GPUs: 8 × fewer GPUs | Helped |
| Use D³RB rather than other selection algorithms (ablation) | ORSO · Continuous control tasks | average normalized task reward | Helped |
| Use Exp3 rather than greedy selection algorithms UCB, ETC, and EG (ablation) | ORSO · Continuous control tasks | average normalized task reward | Helped |
| Use EG rather than naive reward selection (ablation) | ORSO · Continuous control tasks | average normalized task reward | Helped |
| Use ETC rather than naive reward selection (ablation) | ORSO · Continuous control tasks | average normalized task reward | Helped |
| Use D³RB with a fixed reward set of 48 or 96 candidates, without iterative improvement (ablation) | ORSO · Ant | task reward | Helped |
| Use ε-greedy, ETC, or UCB with a fixed reward set of 48 or 96 candidates, without iterative improvement (ablation) | ORSO · Ant | task reward | Hurt |
| Use Exp3 or uniform exploration with a fixed reward set of 48 or 96 candidates, without iterative improvement (ablation) | ORSO · Ant | task reward | Hurt |
| Use 8 reward functions rather than other explored set sizes (ablation) | ORSO · Continuous control tasks | task reward | Helped |
Surprising findings
- Simple selection strategies such as epsilon-greedy and explore-then-commit already substantially outperform naive uniform selection.
- On average ORSO matches or exceeds expert-designed rewards on several tasks.
Limitations
- Relies on a predefined hand-crafted task reward, which is hard to specify for qualitative tasks.
- Experiments explored at most 16 reward functions with resampling and up to 96 without; larger sets left for future work.
- Cannot be parallelized across GPUs in the current formulation.
Experimental setup
Datasets: Isaac Gym simulated tasks (Cartpole, BallBalance, Ant, Humanoid, AllegroHand, ShadowHand)
Benchmarks: Isaac Gym Cartpole Isaac Gym BallBalance Isaac Gym Ant Isaac Gym Humanoid Isaac Gym AllegroHand Isaac Gym ShadowHand
Metrics: normalized task reward time to human-level performance normalized regret
Baselines: No Design (task reward) Human-engineered rewards Naive selection Eureka explore-then-commit epsilon-greedy UCB Exp3
Builds on: Eureka D3RB PPO Exp3 CleanRL
Closest papers by meaning
- Automatic Reward Shaping from Confounded Offline Data (ICML 2025 · similarity 0.90)
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- R*: Efficient Reward Design via Reward Structure Evolution and Parameter Alignment Optimization with Large Language Models (ICML 2025 · similarity 0.89)
- Highly Efficient Self-Adaptive Reward Shaping for Reinforcement Learning (ICLR 2025 · similarity 0.88)
- STARC: A General Framework For Quantifying Differences Between Reward Functions (ICLR 2024 · similarity 0.88)
- Reward Shaping for Reinforcement Learning with An Assistant Reward Agent (ICML 2024 · similarity 0.88)
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