Distillation of Large Language Models via Concrete Score Matching

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Main Authors: Kim, Yeongmin, Shin, Donghyeok, Kang, Mina, Na, Byeonghu, Moon, Il-Chul
Format: Preprint
Published: 2025
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author Kim, Yeongmin
Shin, Donghyeok
Kang, Mina
Na, Byeonghu
Moon, Il-Chul
author_facet Kim, Yeongmin
Shin, Donghyeok
Kang, Mina
Na, Byeonghu
Moon, Il-Chul
contents Large language models (LLMs) deliver remarkable performance but are costly to deploy, motivating knowledge distillation (KD) for efficient inference. Existing KD objectives typically match student and teacher probabilities via softmax, which blurs valuable logit information. While direct logit distillation (DLD) mitigates softmax smoothing, it fails to account for logit shift invariance, thereby restricting the solution space. We propose Concrete Score Distillation (CSD), a discrete score-matching objective that overcomes both softmax-induced smoothing and restrictions on the optimal solution set. We resolve the training instability and quadratic complexity of discrete score-matching in autoregressive LLMs, and the resulting CSD objective aligns relative logit differences across all vocabulary pairs between student and teacher with flexible weighting. We provide both mode-seeking and mode-covering instances within our framework and evaluate CSD on task-agnostic instruction-following and task-specific distillation using GPT-2-1.5B, OpenLLaMA-7B, and GEMMA-7B-IT. Experiments show that CSD consistently surpasses recent KD objectives, achieves favorable fidelity-diversity trade-offs, and yields complementary gains when combined with on-policy techniques, demonstrating its scalability and effectiveness for LLM distillation. Code: https://github.com/aailab-kaist/CSD.
format Preprint
id arxiv_https___arxiv_org_abs_2509_25837
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Distillation of Large Language Models via Concrete Score Matching
Kim, Yeongmin
Shin, Donghyeok
Kang, Mina
Na, Byeonghu
Moon, Il-Chul
Machine Learning
Artificial Intelligence
Large language models (LLMs) deliver remarkable performance but are costly to deploy, motivating knowledge distillation (KD) for efficient inference. Existing KD objectives typically match student and teacher probabilities via softmax, which blurs valuable logit information. While direct logit distillation (DLD) mitigates softmax smoothing, it fails to account for logit shift invariance, thereby restricting the solution space. We propose Concrete Score Distillation (CSD), a discrete score-matching objective that overcomes both softmax-induced smoothing and restrictions on the optimal solution set. We resolve the training instability and quadratic complexity of discrete score-matching in autoregressive LLMs, and the resulting CSD objective aligns relative logit differences across all vocabulary pairs between student and teacher with flexible weighting. We provide both mode-seeking and mode-covering instances within our framework and evaluate CSD on task-agnostic instruction-following and task-specific distillation using GPT-2-1.5B, OpenLLaMA-7B, and GEMMA-7B-IT. Experiments show that CSD consistently surpasses recent KD objectives, achieves favorable fidelity-diversity trade-offs, and yields complementary gains when combined with on-policy techniques, demonstrating its scalability and effectiveness for LLM distillation. Code: https://github.com/aailab-kaist/CSD.
title Distillation of Large Language Models via Concrete Score Matching
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2509.25837