arXiv Computation and Language

Distance generalization in transformers: why bother with positional encoding?

The paper investigates distance generalization in transformer models, focusing on how well they can handle changes in inter-token distances between training and inference while keeping context length fixed. Using two synthetic delay-copy tasks that require copying tokens after finite delays, the authors evaluate the impact of positional encoding schemes (RoPE, ALiBi, and NoPE), the diversity of distances seen during training, and the conditions under which distance transfer learning is beneficial or detrimental. Their comprehensive study highlights the importance of understanding the underlying mechanisms that govern distance generalization in transformers.

arXiv Machine Learning
Oct 22

Copying Under Repetition: From Prefix Matching to Position Hashing

The paper investigates how large language models can accurately copy long repeated strings, a task that standard transformers struggle with due to overrun or truncation. It proposes a two‑layer transformer using RoPE‑style rotations (VO‑rotations) with small prime periods to encode distances modulo primes, enabling the model to distinguish all necessary positions via the Chinese Remainder Theorem and correctly terminate copying. Experiments show that baseline transformers fail on long repeats, while the VO‑based model generalizes to lengths up to about 5005 with near‑perfect accuracy.

By Anxin Guo, Tianlong Huang, Chenxiao Yang, Zhiyuan Li
arXiv Machine Learning
Sep 10

Content-Based Addressing for Long Context

The paper proposes a content‑based addressing scheme for long‑context models that replaces the growing token counter in Rotary Position Embedding (RoPE) with unit‑level addresses derived from the content of each unit. By dividing the token stream into units, the method preserves local RoPE behavior while allowing new units to be addressed via learned content maps, avoiding positional mismatches when extending context length. Experiments on character‑level Tiny Shakespeare show that a model trained on 256‑character contexts achieves lower perplexity at 4096 characters using this scheme, and a second diagnostic demonstrates retrieval of multiple serialized facts.

By Mahesh Godavarti
arXiv AI
2d ago

Quantitative Generalization Bounds for Multi-Layer Transformers: A Few Long Strings can Beat Many Short Ones

The paper presents quantitative generalization bounds for fixed‑precision transformer models, addressing both in‑distribution statistical generalization and length generalization. It derives guarantees based on model parameters, quantization space, and alphabet size, and shows how training length and sample size trade off, with longer training being exponentially more efficient. Experiments confirm the theoretical predictions.

By Marius Henry, Michael Rizvi-Martel, Michael Hahn
arXiv Machine Learning
Oct 9

Remember to Forget: Gated Adaptive Positional Encoding

The paper introduces GAPE (Gated Adaptive Positional Encoding), a drop‑in augmentation for rotary positional encodings that adds content‑aware bias to attention logits while preserving rotary geometry. GAPE uses a query‑dependent gate to contract irrelevant context and a key‑dependent gate to keep salient distant tokens, leading to exponential attenuation of weakly protected context. Experiments show that GAPE improves long‑context robustness, extrapolating up to eight times the training length, and can be retrofitted into a pretrained 7B model without losing benchmark performance.

By Riccardo Ali, Alessio Borgi, Mario Severino, Pietro Li\`o, Christopher Irwin
arXiv Machine Learning
Jun 25

Why Do Accumulated Transformations Extrapolate?

arXiv:2606. 24975v1 Announce Type: new Abstract: PaTH Attention showed that replacing RoPE's position-indexed rotations with accumulated data-dependent Householder reflections yields strong length extrapolation, though performance degrades at extreme context lengths.

By Mahesh Godavarti
arXiv Machine Learning
Sep 25

Transformers as Cross-Task Learners: Shared Structure Drives Sample Efficiency in In-Context Learning

Transformers can learn broad families of tasks during pretraining and adapt to unseen tasks from a short prompt, but a rigorous understanding of this capability is limited. This paper studies how shared cross‑task structure influences the sample complexity of in‑context learning (ICL) by characterizing task‑space complexity through covering numbers, yielding a set of anchor functions that localize unseen tasks and predict responses. The authors construct a Transformer with Softmax attention to approximate this procedure and derive an error bound that separates the effects of pretraining tasks and prompt length, showing that once enough tasks are available the dependence on prompt length becomes dimension‑free.

By Zhongjie Shi, Rongjie Lai, Alexander Cloninger, Wenjing Liao