LLM generation novelty through the lens of semantic similarity

Fuente: arXiv
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Auteurs principaux: Davydov, Philipp, Prabhu, Ameya, Bethge, Matthias, Nguyen, Elisa, Oh, Seong Joon
Format: Preprint
Publié: 2025
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author Davydov, Philipp
Prabhu, Ameya
Bethge, Matthias
Nguyen, Elisa
Oh, Seong Joon
author_facet Davydov, Philipp
Prabhu, Ameya
Bethge, Matthias
Nguyen, Elisa
Oh, Seong Joon
contents Generation novelty is a key indicator of an LLM's ability to generalize, yet measuring it against full pretraining corpora is computationally challenging. Existing evaluations often rely on lexical overlap, failing to detect paraphrased text, or do not consider the full pretraining corpus. We frame novelty as a semantic retrieval problem. This framing enables us to address novelty with modern embedding and indexing pipelines, allowing for efficient analysis at pre-training scale. Specifically, we propose a three-stage framework that retrieves semantically similar samples, reranks them at varying subsequence lengths, and calibrates scores using a human novelty reference for interpretability. We apply this framework to the SmolLM model family and report three key findings: (1) models draw on pre-training data across much longer sequences than previously reported; (2) some task domains systematically promote or suppress generation novelty; and (3) instruction tuning not only alters style but also increases novelty. These results highlight the value of semantic novelty analysis for studying generalization. To support reproducibility and further research, we release ~20 TB of corpus chunks and index artifacts at https://huggingface.co/datasets/stai-tuebingen/faiss-smollm
format Preprint
id arxiv_https___arxiv_org_abs_2510_27313
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle LLM generation novelty through the lens of semantic similarity
Davydov, Philipp
Prabhu, Ameya
Bethge, Matthias
Nguyen, Elisa
Oh, Seong Joon
Machine Learning
Artificial Intelligence
Computation and Language
Generation novelty is a key indicator of an LLM's ability to generalize, yet measuring it against full pretraining corpora is computationally challenging. Existing evaluations often rely on lexical overlap, failing to detect paraphrased text, or do not consider the full pretraining corpus. We frame novelty as a semantic retrieval problem. This framing enables us to address novelty with modern embedding and indexing pipelines, allowing for efficient analysis at pre-training scale. Specifically, we propose a three-stage framework that retrieves semantically similar samples, reranks them at varying subsequence lengths, and calibrates scores using a human novelty reference for interpretability. We apply this framework to the SmolLM model family and report three key findings: (1) models draw on pre-training data across much longer sequences than previously reported; (2) some task domains systematically promote or suppress generation novelty; and (3) instruction tuning not only alters style but also increases novelty. These results highlight the value of semantic novelty analysis for studying generalization. To support reproducibility and further research, we release ~20 TB of corpus chunks and index artifacts at https://huggingface.co/datasets/stai-tuebingen/faiss-smollm
title LLM generation novelty through the lens of semantic similarity
topic Machine Learning
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2510.27313