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I wonder how it relates/compares to https://arxiv.org/abs/2205.08253 https://arxiv.org/abs/2205.08253 : Title: Momentum-Based Policy Gradient with Second-Order
by namibj 3y ago
I wonder how it relates/compares to https://arxiv.org/abs/2205.08253 https://arxiv.org/abs/2205.08253 :
Title:
Momentum-Based Policy Gradient with Second-Order Information
Abstract:
Variance-reduced gradient estimators for policy gradient methods have been one of the main focus of research in the reinforcement learning in recent years as they allow acceleration of the estimation process. We propose a variance-reduced policy-gradient method, called SHARP, which incorporates second-order information into stochastic gradient descent (SGD) using momentum with a time-varying learning rate. SHARP algorithm is parameter-free, achieving ϵ-approximate first-order stationary point with O(ϵ−3) number of trajectories, while using a batch size of O(1) at each iteration. Unlike most previous work, our proposed algorithm does not require importance sampling which can compromise the advantage of variance reduction process. Moreover, the variance of estimation error decays with the fast rate of O(1/t2/3) where t is the number of iterations. Our extensive experimental evaluations show the effectiveness of the proposed algorithm on various control tasks and its advantage over the state of the art in practice.
Though I guess it may be more suitable to training on more interactive tasks like those emphasizing in-context learning, to better exploit RL's ability to adequately deal with tasks where early parts of the model's output are left open, especially when used with curriculum learning to gradually build up capability. Might be more suited to diffusion models than classic GPT 's, though, as RL shines where models have more agency, even if it's just deciding in what order to write the output.
- f_devd 3y agoI'm not too familiar with SHARP but I've implemented SophiaH before, it is effectively mSGD but with the momentum being scaled by inverse of a separate hessian moment with some additional clipping. It works surprisingly well if you can afford the additional memory/compute. It seems like SHARP directly incorporates the hessian directly into the SGD momentum, and increases the 'alpha' or momentum contribution over time.