arXiv:2603.12596cs.LGcs.AI2026-03

用并行多副本聚合提升强化学习优化效率,不增加环境交互。

Optimize Wider, Not Deeper: Consensus Aggregation for Policy Optimization

  • 多个相同策略并行训练后取共识,避免单路径迭代偏差。
  • 在连续控制任务上性能比标准PPO高8.6倍,且样本量不变。
  • 适合追求高效训练的强化学习研究者与工程实践者。

近端策略优化(PPO)通过多轮裁剪梯度下降近似信任区域更新,每轮可能偏离自然梯度方向,产生路径依赖噪声。利用费舍尔信息几何可将策略更新分解为信号(自然梯度投影)和浪费(费舍尔正交残差,消耗信任区域预算但无一阶代理收益)。实验发现,信号随轮次增长趋于饱和,而浪费持续增加,形成优化深度困境。本文提出共识聚合策略优化(CAPO),将计算资源从深度转向宽度:在同一批数据上运行K个仅随机打乱顺序不同的PPO副本,再聚合为共识。研究了欧氏参数空间和自然参数空间(通过对数意见池)两种聚合方式。在自然参数空间中,共识在KL惩罚代理目标上优于平均专家,且信任区域约束更紧;参数平均近似继承这些优势。在连续控制任务中,CAPO在固定样本预算下性能优于PPO及计算量相当的更深基线,最高提升8.6倍。结果表明,无需额外环境交互,通过拓宽而非加深模型即可改进策略优化。

原文摘要 · Abstract (English)

Proximal policy optimization (PPO) approximates the trust region update using multiple epochs of clipped SGD. Each epoch may drift further from the natural gradient direction, creating path-dependent noise. To understand this drift, we can use Fisher information geometry to decompose policy updates into signal (the natural gradient projection) and waste (the Fisher-orthogonal residual that consumes trust region budget without first-order surrogate improvement). Empirically, signal saturates but waste grows with additional epochs, creating an optimization-depth dilemma. We propose Consensus Aggregation for Policy Optimization (CAPO), which redirects compute from depth to width: $K$ PPO replicates are optimized on the same batch, differing only in minibatch shuffling order, and then aggregated into a consensus. We study aggregation in two spaces: Euclidean parameter space, and the natural parameter space of the policy distribution via the logarithmic opinion pool. In natural parameter space, the consensus provably achieves higher KL-penalized surrogate and tighter trust region compliance than the mean expert; parameter averaging inherits these guarantees approximately. On continuous control tasks, CAPO outperforms PPO and compute-matched deeper baselines under fixed sample budgets by up to 8.6x. CAPO demonstrates that policy optimization can be improved by optimizing wider, rather than deeper, without additional environment interactions.

强化学习策略优化并行训练自然梯度

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