arXiv AI

CDAE: Enhancing Perturbation Robustness in Pretrained Language Models with Contrastive Denoising

The paper introduces CDAE, a lightweight Contrastive Denoising Autoencoder that refines pre-trained BERT embeddings by jointly optimizing contrastive and reconstruction objectives. It aims to produce perturbation‑invariant sentence representations, addressing sensitivity to textual perturbations such as synonym substitution, masking, and word dropout. Experiments across various perturbation strategies and strengths show that CDAE consistently maintains higher embedding similarity than original BERT and SimCSE, with the advantage growing as perturbation strength increases.

arXiv Machine Learning
Aug 28

When Is Noise Response Universal? Tokenization as the Hidden Variable in Language Models

The study investigates how textual neural models degrade when inputs contain noise such as typos, OCR errors, or dropped words. It finds that model performance decline is largely consistent across architectures under word‑level noise but diverges under character‑level noise, a difference attributed to tokenization rather than architecture. By applying a short contrastive training recipe, diverse encoders converge to a common robustness curve, enabling prediction of a model’s noise resilience and the ability to enhance robustness at specific noise scales through targeted training.

By Yefan Tao, Gerald Friedland, Luyang Kong
arXiv AI
Aug 18

Invariant Pretraining for Robust Code Representations

arXiv:2608. 15412v1 Announce Type: cross Abstract: Encoder-based code representation models remain widely deployed for discriminative tasks such as clone detection and code classification, where their small size and low inference cost are decisive.

By Yifeng He, Yundi Xu, Christopher Castro Gaw Gonzalo, Zili Wang, Hao Chen
arXiv AI
Sep 28

Achieving Tokenizer Flexibility in Language Models through Heuristic Adaptation and Supertoken Learning

The paper introduces TokenAdapt, a model‑agnostic tokenizer transplantation method that uses a hybrid heuristic to initialize new token embeddings, and a novel pre‑tokenization learning approach for multi‑word Supertokens to improve compression. TokenAdapt combines local subword decomposition and global semantic similarity to preserve semantics while reducing retraining needs. Empirical results show that TokenAdapt outperforms existing baselines such as Transtokenizer and ReTok, achieving lower perplexity ratios and significant compression gains.

By Shaurya Sharthak, Vinayak Pahalwan, Adithya Kamath, Adarsh Shirawalmath
arXiv Machine Learning
Sep 24

Repurposing Pre-trained LLMs as High Fidelity Continuous Text Autoencoders

The paper introduces LLMAE, a technique that transforms a pretrained decoder-only language model into a continuous text autoencoder by inserting a fixed-length latent bottleneck into its internal activations. Using a 270M Gemma 3 model with structured attention masks, LoRA adaptation, and KL regularization, LLMAE achieves near-perfect reconstruction of text sequences up to 1024 tokens. The authors further show that the resulting latent representation can be leveraged to train a latent text diffusion model for detailed image captioning, demonstrating downstream utility.

By Arkanath Pathak, Unnat Jain, Alexander C. Berg
arXiv Computation and Language
Aug 27

Generative vs. Encoder Large Language Models for ASR Evaluation: A Comparative Study

The paper compares encoder‑based and generative decoder‑based large language models for evaluating automatic speech recognition (ASR). It examines BERTScore and SemDist across various LLMs, layers, and pooling strategies, finding that both metrics can strongly correlate with human judgments when properly configured. For generative LLMs, the study explores pairwise hypothesis selection via prompting and direct error classification, showing that while encoder‑based metrics remain competitive, generative models excel in hypothesis comparison and enhance interpretability of ASR evaluation.

By Thibault Ba\~neras-Roux, Shashi Kumar, Driss Khalil, Sergio Burdisso, Petr Motlicek, Shiran Liu, Mickael Rouvier, Jane Wottawa, Richard Dufour