# Non-autoregressive Machine Translation with Probabilistic Context-free Grammar

arXiv: https://arxiv.org/abs/2311.07941 · HTML: https://mlsanity.com/paper/2311.07941/

## Key facts

- Cited by 4 papers in the map (data through 14 Oct 2026).
- Builds on 31 of its 42 references that are in the map.
- First posted on arXiv 14 Nov 2023.

## Builds on (most cited first, 30 of 31)

- [Attention Is All You Need](https://mlsanity.com/paper/1706.03762/) (2017)
- [Neural Machine Translation of Rare Words with Subword Units](https://mlsanity.com/paper/1508.07909/) (2015)
- [A Call for Clarity in Reporting BLEU Scores](https://mlsanity.com/paper/1804.08771/) (2018)
- [fairseq: A Fast, Extensible Toolkit for Sequence Modeling](https://mlsanity.com/paper/1904.01038/) (2019)
- [Non-Autoregressive Neural Machine Translation](https://mlsanity.com/paper/1711.02281/) (2017)
- [Fast Decoding in Sequence Models using Discrete Latent Variables](https://mlsanity.com/paper/1803.03382/) (2018)
- [Glancing Transformer for Non-Autoregressive Neural Machine Translation](https://mlsanity.com/paper/2008.07905/) (2020)
- [Fully Non-autoregressive Neural Machine Translation: Tricks of the Trade](https://mlsanity.com/paper/2012.15833/) (2020)
- [Non-Autoregressive Machine Translation with Latent Alignments](https://mlsanity.com/paper/2004.07437/) (2020)
- [FlowSeq: Non-Autoregressive Conditional Sequence Generation with Generative Flow](https://mlsanity.com/paper/1909.02480/) (2019)
- [End-to-End Non-Autoregressive Neural Machine Translation with Connectionist Temporal Classification](https://mlsanity.com/paper/1811.04719/) (2018)
- [Aligned Cross Entropy for Non-Autoregressive Machine Translation](https://mlsanity.com/paper/2004.01655/) (2020)
- [Latent-Variable Non-Autoregressive Neural Machine Translation with Deterministic Inference Using a Delta Posterior](https://mlsanity.com/paper/1908.07181/) (2019)
- [Order-Agnostic Cross Entropy for Non-Autoregressive Machine Translation](https://mlsanity.com/paper/2106.05093/) (2021)
- [Theory and Experiments on Vector Quantized Autoencoders](https://mlsanity.com/paper/1805.11063/) (2018)
- [Directed Acyclic Transformer for Non-Autoregressive Machine Translation](https://mlsanity.com/paper/2205.07459/) (2022)
- [Guiding Non-Autoregressive Neural Machine Translation Decoding with Reordering Information](https://mlsanity.com/paper/1911.02215/) (2019)
- [Semi-Autoregressive Training Improves Mask-Predict Decoding](https://mlsanity.com/paper/2001.08785/) (2020)
- [Sequence-to-Sequence Learning with Latent Neural Grammars](https://mlsanity.com/paper/2109.01135/) (2021)
- [Non-Autoregressive Translation by Learning Target Categorical Codes](https://mlsanity.com/paper/2103.11405/) (2021)
- [AligNART: Non-autoregressive Neural Machine Translation by Jointly Learning to Estimate Alignment and Translate](https://mlsanity.com/paper/2109.06481/) (2021)
- [textitlatent-GLAT: Glancing at Latent Variables for Parallel Text Generation](https://mlsanity.com/paper/2204.02030/) (2022)
- [Towards String-to-Tree Neural Machine Translation](https://mlsanity.com/paper/1704.04743/) (2017)
- [Syntactically Supervised Transformers for Faster Neural Machine Translation](https://mlsanity.com/paper/1906.02780/) (2019)
- [Non-Autoregressive Machine Translation with Disentangled Context Transformer](https://mlsanity.com/paper/2001.05136/) (2020)
- [Enriching Non-Autoregressive Transformer with Syntactic and SemanticStructures for Neural Machine Translation](https://mlsanity.com/paper/2101.08942/) (2021)
- [Viterbi Decoding of Directed Acyclic Transformer for Non-Autoregressive Machine Translation](https://mlsanity.com/paper/2210.05193/) (2022)
- [Fuzzy Alignments in Directed Acyclic Graph for Non-Autoregressive Machine Translation](https://mlsanity.com/paper/2303.06662/) (2023)
- [DASpeech: Directed Acyclic Transformer for Fast and High-quality Speech-to-Speech Translation](https://mlsanity.com/paper/2310.07403/) (2023)
- [Hierarchical Phrase-based Sequence-to-Sequence Learning](https://mlsanity.com/paper/2211.07906/) (2022)

## Built on by (most cited first, 4 of 4)

- [Continuous Autoregressive Language Models](https://mlsanity.com/paper/2510.27688/) (2025)
- [Beyond Next Token Prediction: Patch-Level Training for Large Language Models](https://mlsanity.com/paper/2407.12665/) (2024)
- [COrAL: Order-Agnostic Language Modeling for Efficient Iterative Refinement](https://mlsanity.com/paper/2410.09675/) (2024)
- [Fully Rotation-Equivariant Spectral-Spatial Learning for Multispectral Object Detection](https://mlsanity.com/paper/2607.05148/) (2026)

## Abstract (arXiv)

Non-autoregressive Transformer(NAT) significantly accelerates the inference of neural machine translation. However, conventional NAT models suffer from limited expression power and performance degradation compared to autoregressive (AT) models due to the assumption of conditional independence among target tokens. To address these limitations, we propose a novel approach called PCFG-NAT, which leverages a specially designed Probabilistic Context-Free Grammar (PCFG) to enhance the ability of NAT models to capture complex dependencies among output tokens. Experimental results on major machine translation benchmarks demonstrate that PCFG-NAT further narrows the gap in translation quality between NAT and AT models. Moreover, PCFG-NAT facilitates a deeper understanding of the generated sentences, addressing the lack of satisfactory explainability in neural machine translation.Code is publicly available at https://github.com/ictnlp/PCFG-NAT.