  As pre-trained models automate many code intelligence tasks, a widely used
paradigm is to fine-tune a model on the task dataset for each programming
language. A recent study reported that multilingual fine-tuning benefits a
range of tasks and models. However, we find that multilingual fine-tuning leads
to performance degradation on recent models UniXcoder and CodeT5.
  To alleviate the potentially catastrophic forgetting issue in multilingual
models, we fix all pre-trained model parameters, insert the parameter-efficient
structure adapter, and fine-tune it. Updating only 0.6\% of the overall
parameters compared to full-model fine-tuning for each programming language,
adapter tuning yields consistent improvements on code search and summarization
tasks, achieving state-of-the-art results. In addition, we experimentally show
its effectiveness in cross-lingual and low-resource scenarios. Multilingual
fine-tuning with 200 samples per programming language approaches the results
fine-tuned with the entire dataset on code summarization. Our experiments on
three probing tasks show that adapter tuning significantly outperforms
full-model fine-tuning and effectively overcomes catastrophic forgetting.

Software Engineering;Artificial Intelligence