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Simple Policy Optimization

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arxiv 2401.16025 v9 pith:6D7RG46C submitted 2024-01-29 cs.LG

Simple Policy Optimization

classification cs.LG
keywords policyoptimizationratioregionsimpletheoreticaltrustclipping
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Model-free reinforcement learning algorithms have seen remarkable progress, but key challenges remain. Trust Region Policy Optimization (TRPO) is known for ensuring monotonic policy improvement through conservative updates within a trust region, backed by strong theoretical guarantees. However, its reliance on complex second-order optimization limits its practical efficiency. Proximal Policy Optimization (PPO) addresses this by simplifying TRPO's approach using ratio clipping, improving efficiency but sacrificing some theoretical robustness. This raises a natural question: Can we combine the strengths of both methods? In this paper, we introduce Simple Policy Optimization (SPO), a novel unconstrained first-order algorithm. By slightly modifying the policy loss used in PPO, SPO can achieve the best of both worlds. Our new objective improves upon ratio clipping, offering stronger theoretical properties and better constraining the probability ratio within the trust region. Empirical results demonstrate that SPO outperforms PPO with a simple implementation, particularly for training large, complex network architectures end-to-end.

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Forward citations

Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Bounded Ratio Reinforcement Learning

    cs.LG 2026-04 conditional novelty 7.0

    BRRL derives an analytic optimal policy for regularized constrained RL that guarantees monotonic improvement and yields the BPO algorithm that matches or exceeds PPO.

  2. Predictive Divergence Masks for LLM RL

    cs.LG 2026-07 conditional novelty 6.0

    Using the first-order change of KL divergence, not the sampled importance ratio, as the mask direction criterion improves LLM RL stability and performance over DPPO.

  3. OGPO: Sample Efficient Full-Finetuning of Generative Control Policies

    cs.LG 2026-05 unverdicted novelty 6.0

    OGPO is a sample-efficient off-policy method for full finetuning of generative control policies that reaches SOTA on robotic manipulation tasks and can recover from poor behavior-cloning initializations without expert data.

  4. OGPO: Sample Efficient Full-Finetuning of Generative Control Policies

    cs.LG 2026-05 unverdicted novelty 6.0

    OGPO enables sample-efficient full-finetuning of generative control policies via off-policy critics and modified PPO, achieving SOTA on robot manipulation tasks while rescuing poorly initialized behavior cloning polic...

  5. Rethinking the Divergence Regularization in LLM RL

    cs.LG 2026-06 unverdicted novelty 5.0

    DRPO introduces a smooth quadratic regularizer on policy divergence that preserves DPPO's trust-region geometry while providing continuous corrective gradients instead of hard masking.

  6. Local Guidance, Global Impact: Gaussian-Reshaped Trust Region Unlocks Behavior Transitions

    cs.LG 2026-06 unverdicted novelty 5.0

    GTR introduces a bounded non-monotonic Gaussian trust region and Mixture Gaussian Anchor to enable effective behavior transitions in non-stationary RL where standard PPO fails.

  7. Ratio-Variance Regularized Policy Optimization

    cs.LG 2026-05 unverdicted novelty 5.0

    R²VPO uses ratio-variance regularization as a distributional soft brake on policy updates, claiming better performance than PPO on math reasoning and robotic control without hard clipping.