From Local to Global: Revisiting Structured Pruning Paradigms for Large Language Models
Paper · 2026 · Ziyan Wang, Enmao Diao, Qi Le et al.
Summary
Most structured pruning methods for LLMs work locally. They rebuild each layer's outputs separately from calibration data. This keeps perplexity and generic zero-shot behaviour reasonable, but it does not tie the pruning to a downstream task, so task-specific calibration data adds little. The authors return to global pruning and propose GISP (Global Iterative Structured Pruning). It is a post-training method that drops attention heads and MLP channels. Their importance scores are first-order, loss-based estimates, combined per structure and normalized within blocks. Pruning proceeds gradually over a scheduled series of ratios, with no fine-tuning between steps. This avoids the instability of one-shot global pruning and produces nested subnetworks: one pruning run gives models at many sparsity levels ("prune-once, deploy-many"). The loss can be perplexity or a task-oriented margin objective, so pruning can follow a target task. On several Llama, Mistral and reasoning models, GISP lowers perplexity and raises accuracy compared with local baselines, most clearly at high sparsity. This makes compact, deployable LLMs more practical.
Key points
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Models and benchmarks: Llama2-7B/13B, Llama3-8B and Mistral-0.3-7B were tested on WikiText-2 perplexity and downstream accuracy (CMQA). The largest gains appear at 40–50% sparsity.
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Reasoning models: On DeepSeek-R1-Distill-Llama-3-8B and Qwen3-8B, task-aligned calibration on GSM8K clearly improves exact-match accuracy. With default C4 calibration, the Wanda-sp baseline drops to 0% at 20% pruning.
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LoRA fine-tuning: Pruned Llama2-7B models were fine-tuned with LoRA on 2M extra CMQA samples, and GISP stays ahead of Wanda-sp:
Sparsity Wanda-sp GISP 20% 67.43 68.93 40% 58.66 60.52 -
Calibration robustness: Cutting the 512K-token CMQA calibration set to 1% shifts accuracy by at most 0.66 points. Resampling with different seeds gives a standard deviation of at most 0.56.
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Limitations:
- Gradient-based scoring is costly in memory and compute.
- Mixture-of-Experts models have not yet been tested.
Institutions
Fields, topics and concepts
📚 Shelves 5The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksArts and Humanities · 16,039 worksLanguage and Linguistics · 15,891 worksComputer Vision and Pattern Recognition · 2,869 works
🧭 Topics 2Research subjects and languages the work is about.Language models & pretraining · 3,320 worksEfficient models & compression · 242 works
Cite
Cite as Ziyan Wang, Enmao Diao, Qi Le, Pu Wang, Minwoo Lee, Shu-ping Yeh, Evgeny Stupachenko, Hao Feng and Li Yang. 2026. From Local to Global: Revisiting Structured Pruning Paradigms for Large Language Models. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers).
@inproceedings{wang2026local,
title = {{From Local to Global: Revisiting Structured Pruning Paradigms for Large Language Models}},
author = {Ziyan Wang, Enmao Diao, Qi Le, Pu Wang, Minwoo Lee, Shu-ping Yeh, Evgeny Stupachenko, Hao Feng and Li Yang},
booktitle = {Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)},
year = {2026},
doi = {10.18653/v1/2026.acl-long.1653},
url = {https://doi.org/10.18653/v1/2026.acl-long.1653}
}References
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