OneRec: Unifying Retrieve and Rank with Generative Recommender and
  Iterative Preference Alignment
Authors: name: Jiaxin Deng, name: Shiyao Wang, name: Kuo Cai, name: Lejian Ren, name: Qigen Hu, name: Weifeng Ding, name: Qiang Luo, name: Guorui Zhou

Recently, generative retrieval-based recommendation systems have emerged as a
promising paradigm. However, most modern recommender systems adopt a
retrieve-and-rank strategy, where the generative model functions only as a
selector during the retrieval stage. In this paper, we propose OneRec, which
replaces the cascaded learning framework with a unified generative model. To
the best of our knowledge, this is the first end-to-end generative model that
significantly surpasses current complex and well-designed recommender systems
in real-world scenarios. Specifically, OneRec includes: 1) an encoder-decoder
structure, which encodes the user's historical behavior sequences and gradually
decodes the videos that the user may be interested in. We adopt sparse
Mixture-of-Experts (MoE) to scale model capacity without proportionally
increasing computational FLOPs. 2) a session-wise generation approach. In
contrast to traditional next-item prediction, we propose a session-wise
generation, which is more elegant and contextually coherent than point-by-point
generation that relies on hand-crafted rules to properly combine the generated
results. 3) an Iterative Preference Alignment module combined with Direct
Preference Optimization (DPO) to enhance the quality of the generated results.
Unlike DPO in NLP, a recommendation system typically has only one opportunity
to display results for each user's browsing request, making it impossible to
obtain positive and negative samples simultaneously. To address this
limitation, We design a reward model to simulate user generation and customize
the sampling strategy. Extensive experiments have demonstrated that a limited
number of DPO samples can align user interest preferences and significantly
improve the quality of generated results. We deployed OneRec in the main scene
of Kuaishou, achieving a 1.6\% increase in watch-time, which is a substantial
improvement.