Dropping the Anchor: Statistical Context Summarization for Distributed Systems via Pulsar Attention

Aryan Sood, Shantanu Acharya, Gaurav Kumar Nayak


Abstract
Inference with large language models (LLMs) on long sequences is computationally expensive due to the quadratic complexity of self-attention. Distributed blockwise methods such as Star Attention reduce this cost by sharding context across hosts, but rely on prepending a static, content-blind copy of the first block to every host. We propose Pulsar Attention, which replaces the static anchor with two lightweight, content-aware components: a small attention-sink prefix that stabilizes softmax, and compact cross-block summaries built via a Max-IDF heuristic that selects chunks containing globally rare tokens. This reduces the Phase 1 per-GPU FLOPs by up to 3.3× over Star Attention while retaining an identical KV cache footprint. On RULER with Llama-3.1-8B-Instruct, Pulsar Attention outperforms Star Attention at sequence lengths up to 128K tokens and remains competitive with dense attention across most tasks, with task-dependent absolute gains of up to 4.7% over the dense baseline.
Anthology ID:
2026.findings-emnlp.1330
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
28176–28191
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1330/
DOI:
10.18653/2026.findings-emnlp.1330
Bibkey:
Cite (ACL):
Aryan Sood, Shantanu Acharya, and Gaurav Kumar Nayak. 2026. Dropping the Anchor: Statistical Context Summarization for Distributed Systems via Pulsar Attention. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 28176–28191, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Dropping the Anchor: Statistical Context Summarization for Distributed Systems via Pulsar Attention (Sood et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1330.pdf