arXiv Computation and Language

Provably Tractable NFA-Constrained Language Generation via HMMs

The paper introduces NFA-LM, a polynomial‑time method for generating language model outputs that satisfy nondeterministic finite automaton (NFA) constraints. It leverages recent results that the #NFA counting problem admits a fully polynomial randomized approximation scheme, providing theoretical guarantees under mild assumptions. Experiments demonstrate that NFA‑LM produces high‑quality outputs efficiently while keeping approximation error bounded.

arXiv Computation and Language
3d ago

Making Grid Beam Search Less Greedy

arXiv:2609.39368v1 Announce Type: new Abstract: A common formalism for constraining the output of autoregressive text generation models involves lexical constraints, words or phrases which are requir...

By Sean Papay, Roman Klinger
arXiv AI
Jun 4

Constrained Adaptive Rejection Sampling

arXiv:2510. 01902v2 Announce Type: replace Abstract: Language Models (LMs) are increasingly used in applications where generated outputs must satisfy strict semantic or syntactic constraints.

By Pawe{\l} Parys, Sairam Vaidya, Taylor Berg-Kirkpatrick, Loris D'Antoni
arXiv AI
Sep 4

Grammar-Aligned Decoding

The paper introduces Grammar‑Aligned Decoding (GAD), addressing the issue that conventional grammar‑constrained decoding (GCD) can distort a large language model’s probability distribution, yielding grammatical but low‑likelihood outputs. GAD proposes an adaptive sampling method, Approximate Expected Futures (ASAp), which uses prior samples to over‑approximate future grammaticality, ensuring outputs remain both grammatical and faithful to the model’s conditional probabilities. Experiments on code generation and structured NLP tasks demonstrate that ASAp often produces higher‑likelihood outputs than existing GCD techniques while still enforcing the required grammatical constraints.

By Kanghee Park, Jiayu Wang, Taylor Berg-Kirkpatrick, Nadia Polikarpova, Loris D'Antoni