SynCode: LLM Generation with Grammar Augmentation (2403.01632v4)

Abstract: LLMs are widely used in complex AI applications. These applications underscore the need for LLM outputs to adhere to a specific format, for their integration with other components in the systems. Typically the format rules e.g., for data serialization formats such as JSON, YAML, or Code in Programming Language are expressed as context-free grammar (CFG). Due to the hallucinations and unreliability of LLMs, instructing LLMs to adhere to specified syntax becomes an increasingly important challenge. We present SynCode, a novel framework for efficient and general syntactical decoding with LLMs, to address this challenge. SynCode ensures soundness and completeness with respect to the CFG of a formal language, effectively retaining valid tokens while filtering out invalid ones. SynCode uses an offline-constructed, efficient lookup table, the DFA mask store, derived from the DFA of the language's grammar for efficient generation. SynCode seamlessly integrates with any language defined by CFG, as evidenced by experiments focusing on generating JSON, Python, and Go outputs. Our experiments evaluating the effectiveness of SynCode for JSON generation demonstrate that SynCode eliminates all syntax errors and significantly outperforms state-of-the-art baselines. Furthermore, our results underscore how SynCode significantly reduces 96.07% of syntax errors in generated Python and Go code, showcasing its substantial impact on enhancing syntactical precision in LLM generation. Our code is available at https://github.com/uiuc-focal-lab/syncode

Enhancing Syntactical Accuracy in LLM-Generated Code with Grammar Augmentation

Introduction

The exponential rise in capabilities and applications of LLMs has been instrumental in automating various aspects of software development, including code generation. However, the integrity of LLM-generated code, specifically its adherence to programming language syntax, remains a significant challenge. Existing methods, despite their innovative approaches, encounter limitations in speed, scalability, and applicability, particularly when transitioning from domain-specific languages (DSLs) to general-purpose programming languages. In light of these limitations, we introduce SynCode, a novel framework designed to address the gap in generating syntactically correct code across a wider spectrum of programming languages effectively.

SynCode Framework

SynCode operates by leveraging the grammar of programming languages, incorporating an offline-constructed DFA mask store based on the grammar's terminals. This strategic approach allows SynCode to integrate effortlessly with various LLM decoding algorithms, offering a robust solution for enhancing syntactical precision in code generation. The core innovation lies in SynCode's ability to iteratively parse partially generated code, identify syntactically valid token sequences via an efficient DFA mask store lookup, and consequently guide the LLM towards generating syntactically sound code.

Experimental Evaluation

Our evaluation spans several state-of-the-art LLMs, including CodeGen, WizardCoder, and Llama, applying SynCode to both Python and Go languages using the HumanEval and MBXP datasets. The results are compelling, demonstrating an average reduction of syntax errors by 96.07% across different models and languages compared to standard generation methods. Notably, SynCode exhibits its substantial impact in scenarios where programming languages are underrepresented in the LLM's training data, significantly decreasing the syntax error rate and thereby underscoring its versatility and effectiveness.

Theoretical Underpinnings

SynCode's foundational strength is rooted in its sound and complete approach towards syntactical decoding, given the context-free grammar (CFG) of the target programming language. We rigorously define the constructs of partial programs, acceptable sequences, and DFA mask stores, elaborating on how SynCode judiciously employs these constructs to ascertain syntactically valid extensions of partially generated code. Through theorem-based validations, we establish SynCode's soundness—its capability to retain all syntactically valid tokens, and under specific conditions, its completeness in rejecting syntactically invalid tokens.

Practical Implications and Future Outlook

SynCode not only marks a significant advancement in the quality of LLM-generated code but also opens avenues for further research and development towards fully realizing the potential of LLMs in software development. Its methodological efficiency and scalability portend well for its integration into existing development workflows, potentially reducing debugging efforts and accelerating the development cycle. Looking ahead, the exploration of SynCode's application to a broader array of programming languages and its adaptability to evolving LLM architectures present promising areas for further investigation.

Conclusion

In summation, SynCode represents a pivotal stride towards mitigating the syntactical errors prevalent in LLM-generated code. By marrying the intrinsic grammar of programming languages with the generative prowess of LLMs, SynCode not only illuminates the path to more syntactically accurate code generation but also reinforces the symbiotic potential between formal language theory and machine learning in advancing software development methodologies.