Domain Mixture Design via Log-Likelihood Differences for Aligning Language Models with a Target Model

Fuente: arXiv
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Auteurs principaux: Kishino, Ryo, Shiomi, Riku, Yamagiwa, Hiroaki, Oyama, Momose, Shimodaira, Hidetoshi
Format: Preprint
Publié: 2026
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author Kishino, Ryo
Shiomi, Riku
Yamagiwa, Hiroaki
Oyama, Momose
Shimodaira, Hidetoshi
author_facet Kishino, Ryo
Shiomi, Riku
Yamagiwa, Hiroaki
Oyama, Momose
Shimodaira, Hidetoshi
contents Instead of directly distilling a language model, this study addresses the problem of aligning a base model with a target model in distribution by designing the domain mixture of training data for pretraining or continued pretraining as a fixed training recipe. We propose a method for determining domain weights by viewing models as points in log-likelihood space and aligning the training update direction with the direction toward the target model. Experiments with NanoGPT show that the proposed method consistently reduces the KL divergence to the target model compared with uniform weighting over the Pile. Although knowledge distillation remains more effective when available, the proposed method still achieves meaningful alignment, and downstream task performance also tends to become closer to that of the target model.
format Preprint
id arxiv_https___arxiv_org_abs_2603_16622
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Domain Mixture Design via Log-Likelihood Differences for Aligning Language Models with a Target Model
Kishino, Ryo
Shiomi, Riku
Yamagiwa, Hiroaki
Oyama, Momose
Shimodaira, Hidetoshi
Computation and Language
Instead of directly distilling a language model, this study addresses the problem of aligning a base model with a target model in distribution by designing the domain mixture of training data for pretraining or continued pretraining as a fixed training recipe. We propose a method for determining domain weights by viewing models as points in log-likelihood space and aligning the training update direction with the direction toward the target model. Experiments with NanoGPT show that the proposed method consistently reduces the KL divergence to the target model compared with uniform weighting over the Pile. Although knowledge distillation remains more effective when available, the proposed method still achieves meaningful alignment, and downstream task performance also tends to become closer to that of the target model.
title Domain Mixture Design via Log-Likelihood Differences for Aligning Language Models with a Target Model
topic Computation and Language
url https://arxiv.org/abs/2603.16622