arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2310.03419cs.LGcs.AI

生成流网络的预训练与微调

Pre-Training and Fine-Tuning Generative Flow Networks

Mila(米拉研究所);Université de Montréal(蒙特利尔大学);CIFAR AI Chair(加拿大高等研究院人工智能讲席)

Ling Pan, Moksh Jain, Kanika Madan, Yoshua Bengio

AI总结:

针对生成流网络(GFlowNets)依赖外部奖励训练、难以高效适配下游任务的问题,提出无奖励预训练的结果条件GFlowNet(OC-GFN)及基于摊销预测器的高效微调方法,实验验证其适配与模式发现效率更优,为GFlowNets预训练研究奠定基础。

摘要:

生成流网络(Generative Flow Networks, GFlowNets)是一种摊销采样器,它学习随机策略,从给定的非归一化奖励分布中按顺序生成组合对象。它们能够生成多样化的高奖励对象集合,这在科学发现任务中是一项重要考量。然而,由于GFlowNets通常基于给定的外部奖励函数进行训练,如何利用预训练的优势、以无监督方式训练GFlowNets以高效适配下游任务,仍是一个重要的开放性挑战。受各领域无监督预训练近期取得的成功启发,我们提出了一种GFlowNets无奖励预训练的新方法。通过将训练构建为自监督问题,我们提出了结果条件生成流网络(outcome-conditioned GFlowNet, OC-GFN),用于学习探索候选空间。具体而言,OC-GFN学习到达任意目标结果,类似于强化学习中的目标条件策略。我们证明,预训练后的OC-GFN模型可以直接提取出能够从下游任务中任意新奖励函数采样的策略。尽管如此,让OC-GFN适配下游特定任务奖励的过程中,需要对所有可能的结果进行难以处理的边缘化计算。我们提出了一种新的近似该边缘化计算的方法,即学习一个摊销预测器以实现高效微调。大量实验结果验证了我们方法的有效性,证明了OC-GFN预训练的效果,以及它快速适配下游任务、更高效发现模式的能力。这项工作可为进一步探索GFlowNets背景下的预训练策略奠定基础。

英文摘要:

Generative Flow Networks (GFlowNets) are amortized samplers that learn stochastic policies to sequentially generate compositional objects from a given unnormalized reward distribution. They can generate diverse sets of high-reward objects, which is an important consideration in scientific discovery tasks. However, as they are typically trained from a given extrinsic reward function, it remains an important open challenge about how to leverage the power of pre-training and train GFlowNets in an unsupervised fashion for efficient adaptation to downstream tasks. Inspired by recent successes of unsupervised pre-training in various domains, we introduce a novel approach for reward-free pre-training of GFlowNets. By framing the training as a self-supervised problem, we propose an outcome-conditioned GFlowNet (OC-GFN) that learns to explore the candidate space. Specifically, OC-GFN learns to reach any targeted outcomes, akin to goal-conditioned policies in reinforcement learning. We show that the pre-trained OC-GFN model can allow for a direct extraction of a policy capable of sampling from any new reward functions in downstream tasks. Nonetheless, adapting OC-GFN on a downstream task-specific reward involves an intractable marginalization over possible outcomes. We propose a novel way to approximate this marginalization by learning an amortized predictor enabling efficient fine-tuning. Extensive experimental results validate the efficacy of our approach, demonstrating the effectiveness of pre-training the OC-GFN, and its ability to swiftly adapt to downstream tasks and discover modes more efficiently. This work may serve as a foundation for further exploration of pre-training strategies in the context of GFlowNets.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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