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Investigating Layer Importance in Large Language Models

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arxiv 2409.14381 v1 pith:VITLZQIE submitted 2024-09-22 cs.CL cs.LG

Investigating Layer Importance in Large Language Models

classification cs.CL cs.LG
keywords layersllmscornerstonelayermodelsperformanceimportanceinvestigating
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Large language models (LLMs) have gained increasing attention due to their prominent ability to understand and process texts. Nevertheless, LLMs largely remain opaque. The lack of understanding of LLMs has obstructed the deployment in safety-critical scenarios and hindered the development of better models. In this study, we advance the understanding of LLM by investigating the significance of individual layers in LLMs. We propose an efficient sampling method to faithfully evaluate the importance of layers using Shapley values, a widely used explanation framework in feature attribution and data valuation. In addition, we conduct layer ablation experiments to assess the performance degradation resulting from the exclusion of specific layers. Our findings reveal the existence of cornerstone layers, wherein certain early layers can exhibit a dominant contribution over others. Removing one cornerstone layer leads to a drastic collapse of the model performance, often reducing it to random guessing. Conversely, removing non-cornerstone layers results in only marginal performance changes. This study identifies cornerstone layers in LLMs and underscores their critical role for future research.

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Cited by 8 Pith papers

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