Diversifying to Verify: When Task-Equivalent Programs Differ in Verifiability

2026-07-10

AI Summary

This work addresses the significant disparity in verifiability among semantically equivalent yet structurally diverse programs, a key bottleneck in generating high-assurance software. The authors propose Diversify2Verify, a novel approach that leverages large language models to synthesize diverse recursive and imperative implementations of the same task, integrates the Why3 platform for automatic contract inference and formal verification, and introduces a verifier-guided annotation repair mechanism to enhance verifiability. This study is the first to systematically expose the verifiability gap across equivalent program variants and establishes a new paradigm wherein implementation diversity drives improved verification success. Evaluated on a benchmark of 73 tasks, the method yields 154 verifiable programs after two rounds of repair, with at least one successfully verified variant for 67.1% of the tasks—substantially outperforming baseline approaches.

Abstract

Program verification is crucial for software correctness, but producing fully verified programs remains difficult in practice. This paper studies whether implementation structure affects automated verifiability when multiple generated programs are intended to satisfy the same task-level semantics. We present Diversify2Verify, a staged LLM-based pipeline for Why3 that infers representation-specific contracts, generates and tests diverse recursive and imperative array/list implementations, and attempts verification with bounded verifier-guided annotation repair. We also construct a verification-oriented benchmark of 73 tasks over integers, arrays, and lists, yielding 292 implementation variants. Diversify2Verify verifies 96 artifacts initially and 154 after two repair passes, improving artifact-level verification from 32.9% to 52.7%. At the task level, at least one variant verifies for 49 of 73 tasks, a 67.1% success rate. These results show that task-equivalent implementations can differ substantially in verifiability and that implementation diversity helps find verification-friendly artifacts.

Problem

• program verification
• implementation diversity
• automated verifiability
• task-equivalent programs
• verification-friendly artifacts

Innovation

• program verification
• implementation diversity
• LLM-based synthesis
• verifiability
• contract inference