Thoth: Mid-Training Bridges LLMs to Time Series Understanding

Fuente: arXiv
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Autori principali: Lin, Jiafeng, Wang, Yuxuan, Wu, Jialong, Luo, Huakun, Pei, Zhongyi, Wang, Jianmin
Natura: Preprint
Pubblicazione: 2026
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author Lin, Jiafeng
Wang, Yuxuan
Wu, Jialong
Luo, Huakun
Pei, Zhongyi
Wang, Jianmin
author_facet Lin, Jiafeng
Wang, Yuxuan
Wu, Jialong
Luo, Huakun
Pei, Zhongyi
Wang, Jianmin
contents Large Language Models (LLMs) have demonstrated remarkable success in general-purpose reasoning. However, they still struggle to understand and reason about time series data, which limits their effectiveness in decision-making scenarios that depend on temporal dynamics. In this paper, we propose Thoth, the first family of mid-trained LLMs with general-purpose time series understanding capabilities. As a pivotal intermediate stage, mid-training achieves task- and domain-agnostic alignment between time series and natural language, for which we construct Book-of-Thoth, a high-quality, time-series-centric mid-training corpus. Book-of-Thoth enables both time-series-to-text and text-to-time-series generation, equipping LLMs with a foundational grasp of temporal patterns. To better evaluate advanced reasoning capabilities, we further present KnoTS, a novel benchmark of knowledge-intensive time series understanding, designed for joint reasoning over temporal patterns and domain knowledge. Extensive experiments demonstrate that mid-training with Book-of-Thoth enables Thoth to significantly outperform its base model and advanced LLMs across a range of time series question answering benchmarks. Moreover, Thoth exhibits superior capabilities when fine-tuned under data scarcity, underscoring the effectiveness of mid-training for time series understanding. Code is available at: https://github.com/thuml/Thoth.
format Preprint
id arxiv_https___arxiv_org_abs_2603_01042
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Thoth: Mid-Training Bridges LLMs to Time Series Understanding
Lin, Jiafeng
Wang, Yuxuan
Wu, Jialong
Luo, Huakun
Pei, Zhongyi
Wang, Jianmin
Computation and Language
Artificial Intelligence
Machine Learning
Large Language Models (LLMs) have demonstrated remarkable success in general-purpose reasoning. However, they still struggle to understand and reason about time series data, which limits their effectiveness in decision-making scenarios that depend on temporal dynamics. In this paper, we propose Thoth, the first family of mid-trained LLMs with general-purpose time series understanding capabilities. As a pivotal intermediate stage, mid-training achieves task- and domain-agnostic alignment between time series and natural language, for which we construct Book-of-Thoth, a high-quality, time-series-centric mid-training corpus. Book-of-Thoth enables both time-series-to-text and text-to-time-series generation, equipping LLMs with a foundational grasp of temporal patterns. To better evaluate advanced reasoning capabilities, we further present KnoTS, a novel benchmark of knowledge-intensive time series understanding, designed for joint reasoning over temporal patterns and domain knowledge. Extensive experiments demonstrate that mid-training with Book-of-Thoth enables Thoth to significantly outperform its base model and advanced LLMs across a range of time series question answering benchmarks. Moreover, Thoth exhibits superior capabilities when fine-tuned under data scarcity, underscoring the effectiveness of mid-training for time series understanding. Code is available at: https://github.com/thuml/Thoth.
title Thoth: Mid-Training Bridges LLMs to Time Series Understanding
topic Computation and Language
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2603.01042