FormalEvolve: Neuro-Symbolic Evolutionary Search for Diverse Autoformalization

Haijian Lu, Wei Wang, Jing Liu


Abstract
Autoformalization aims to produce formal statements that compile and faithfully preserve the intended meaning of informal mathematics. Yet standard single-output evaluation collapses this many-to-many structure into a single prediction. For downstream proving, this granularity is too coarse: a formal statement is not merely a faithful translation endpoint, but also a prover-facing interface whose structure can alter proof search under a fixed budget. We therefore recast autoformalization as budgeted test-time search: FormalEvolve maintains a compilation-feasible archive for reuse and returns a deduplicated, semantically accepted repertoire for evaluation and downstream proving. It expands the archive with LLM-driven mutation, crossover, bounded patch repair, and symbolic abstract syntax tree (AST) rewrites for structural diversity. Under a generator-call budget of T=100 with a fixed LLM semantic judge, FormalEvolve reaches SH@100 of 58.0% on CombiBench and 84.9% on ProofNet, improving over all no-archive controls while reducing the cross-problem concentration of semantic successes. Under a fixed B=64 prover budget, these repertoires improve theorem-complete proving over the matched no-archive control. Additional stronger-base statement-generation experiments show that archive-search gains persist with stronger seed and repair models.
Anthology ID:
2026.findings-emnlp.317
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
6694–6722
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.317/
DOI:
Bibkey:
Cite (ACL):
Haijian Lu, Wei Wang, and Jing Liu. 2026. FormalEvolve: Neuro-Symbolic Evolutionary Search for Diverse Autoformalization. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 6694–6722, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
FormalEvolve: Neuro-Symbolic Evolutionary Search for Diverse Autoformalization (Lu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.317.pdf