Retriever and Ranker Framework with Probabilistic Hard Negative Sampling for Code Search
share
Pretrained Language Models (PLMs) have emerged as the state-of-the-art paradigm for code search tasks. The paradigm involves pretraining the model on search-irrelevant tasks such as masked language modeling, followed by the finetuning stage, which focuses on the search-relevant task. The typical finetuning method is to employ a dual-encoder architecture to encode semantic embeddings of query and code separately, and then calculate their similarity based on the embeddings. However, the typical dual-encoder architecture falls short in modeling token-level interactions between query and code, which limits the model's capabilities. In this paper, we propose a novel approach to address this limitation, introducing a cross-encoder architecture for code search that jointly encodes the semantic matching of query and code. We further introduce a Retriever-Ranker (RR) framework that cascades the dual-encoder and cross-encoder to promote the efficiency of evaluation and online serving. Moreover, we present a probabilistic hard negative sampling method to improve the cross-encoder's ability to distinguish hard negative codes, which further enhances the cascade RR framework. Experiments on four datasets using three code PLMs demonstrate the superiority of our proposed method.
READ FULL TEXT
