CodeT5+: Open Code Large Language Models for Code Understanding and
  Generation
Authors: name: Yue Wang, name: Hung Le, name: Akhilesh Deepak Gotmare, name: Nghi D. Q. Bui, name: Junnan Li, name: Steven C. H. Hoi

Large language models (LLMs) pretrained on vast source code have achieved
prominent progress in code intelligence. However, existing code LLMs have two
main limitations in terms of architecture and pretraining tasks. First, they
often adopt a specific architecture (encoder-only or decoder-only) or rely on a
unified encoder-decoder network for different downstream tasks. The former
paradigm is limited by inflexibility in applications while in the latter, the
model is treated as a single system for all tasks, leading to suboptimal
performance on a subset of tasks. Secondly, they often employ a limited set of
pretraining objectives which might not be relevant to some downstream tasks and
hence result in substantial performance degrade. To address these limitations,
we propose ``CodeT5+'', a family of encoder-decoder LLMs for code in which
component modules can be flexibly combined to suit a wide range of downstream
code tasks. Such flexibility is enabled by our proposed mixture of pretraining
objectives to mitigate the pretrain-finetune discrepancy. These objectives
cover span denoising, contrastive learning, text-code matching, and causal LM
pretraining tasks, on both unimodal and bimodal multilingual code corpora.
Furthermore, we propose to initialize CodeT5+ with frozen off-the-shelf LLMs
without training from scratch to efficiently scale up our models, and explore
instruction-tuning to align with natural language instructions. We extensively
evaluate CodeT5+ on over 20 code-related benchmarks in different settings,
including zero-shot, finetuning, and instruction-tuning. We observe
state-of-the-art (SoTA) model performance on various code-related tasks, such
as code generation and completion, math programming, and text-to-code retrieval
tasks. Particularly, our instruction-tuned CodeT5+ 16B achieves new SoTA
results on HumanEval code generation task against other open code LLMs.