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arxiv: 2505.11017 · v2 · submitted 2025-05-16 · 💻 cs.LG

Logo-LLM: Local and Global Modeling with Large Language Models for Time Series Forecasting

Pith reviewed 2026-05-22 15:12 UTC · model grok-4.3

classification 💻 cs.LG
keywords time series forecastinglarge language modelslocal global modelingmulti-scale featuresfew-shot learningzero-shot forecastingmixer modules
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The pith

Extracting local dynamics from shallow LLM layers and global trends from deeper layers improves time series forecasting accuracy.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper addresses a limitation in current LLM-based time series forecasting methods that only use the final layer output. It finds that shallow layers focus on local short-term variations while deeper layers handle global long-term dependencies. To make use of this, the authors add lightweight modules called Local-Mixer and Global-Mixer to combine these features from multiple layers with the time series input. Experiments on various benchmarks show this leads to better predictions, particularly in cases with limited training data, and does so efficiently.

Core claim

Through empirical analysis the paper establishes that shallow layers of LLMs capture local dynamics in time series while deeper layers encode global trends. Logo-LLM uses this by extracting multi-scale features and integrating them with Local-Mixer and Global-Mixer modules, resulting in superior performance across benchmarks and strong generalization in few-shot and zero-shot settings at low computational cost.

What carries the argument

The layer-specific feature extraction from pre-trained LLMs paired with Local-Mixer and Global-Mixer modules for aligning and integrating local and global temporal features.

Load-bearing premise

That the local-global separation observed in LLM layers for time series is a general property that can be reliably exploited.

What would settle it

If future tests on diverse time series data show that using only the final LLM layer performs as well or better than the multi-layer approach with mixers, the advantage would be called into question.

Figures

Figures reproduced from arXiv: 2505.11017 by Cheng Chen, Dongyue Guo, Wenjie Ou, Yi Lin, Zhishuo Zhao.

Figure 1
Figure 1. Figure 1: Comparison of LLM usage paradigms. Prior works treat LLMs as black-box encoders and use only the last-layer feature. Our method explicitly extracts features from multiple layers, leveraging shallow-layer features for local modeling and deep-layer features for global modeling, enabling a more fine-grained understanding of temporal dynamics. Inspired by the above insights, we propose a Local and global model… view at source ↗
Figure 2
Figure 2. Figure 2: Overview of the proposed Logo-LLM framework. Logo-LLM extracts intermediate representations from multiple layers of a pre-trained LLM to explicitly model local and global temporal patterns. Two specialized Mixer modules are introduced to align these hierarchical features with the temporal input, enabling fine-grained modeling of local and global variations. Most LLM parameters are kept frozen, enabling eff… view at source ↗
Figure 3
Figure 3. Figure 3: Comparison of Logo-LLM and CALF with various layers on ETTh1 and ETTh2 datasets. The prediction length is set as {96, 192}. fine-grained variations is balanced. This observation validates our design of selectively leveraging shallow and deep layer representations, rather than relying on the last layer. Impact of Local Feature Layer Selection. To investigate the optimal layer for extracting local representa… view at source ↗
Figure 4
Figure 4. Figure 4: Visualization of different selections {1, 2, 3, 4, 5, 6} about local feature layer on ETTh1, ETTm2, and ETTh2. The prediction length is set as 96 with input length 𝐿 = 96. We observe that using the first-layer output as a local feature yields the best performance and performance gradually deteriorates or plateaus when deeper layers are used. This finding supports our design choice and aligns with the repre… view at source ↗
Figure 5
Figure 5. Figure 5: Similarity matrices of each patch across Transformer layers in (a) Logo-LLM (b) CALF and (c) Time-LLM, illustrating that shallow layers exhibit pronounced local patterns while deeper layers capture broader global dependencies. dependencies, are not unique to GPT-2 (Radford et al. (2019)). Instead, this capability exists as a universal intrinsic property of LLMs, independent of specific architectural design… view at source ↗
read the original abstract

Time series forecasting is critical across multiple domains, where time series data exhibit both local patterns and global dependencies. While Transformer-based methods effectively capture global dependencies, they often overlook short-term local variations in time series. Recent methods that adapt large language models (LLMs) into time series forecasting inherit this limitation by treating LLMs as black-box encoders, relying solely on the final-layer output and underutilizing hierarchical representations. To address this limitation, we propose Logo-LLM, a novel LLM-based framework that explicitly extracts and models multi-scale temporal features from different layers of a pre-trained LLM. Through empirical analysis, we show that shallow layers of LLMs capture local dynamics in time series, while deeper layers encode global trends. Moreover, Logo-LLM introduces lightweight Local-Mixer and Global-Mixer modules to align and integrate features with the temporal input across layers. Extensive experiments demonstrate that Logo-LLM achieves superior performance across diverse benchmarks, with strong generalization in few-shot and zero-shot settings while maintaining low computational overhead.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript introduces Logo-LLM, a framework that extracts multi-scale temporal features from different layers of a pre-trained LLM for time series forecasting instead of treating the LLM as a black-box final-layer encoder. It claims through empirical analysis that shallow layers capture local dynamics while deeper layers encode global trends, introduces lightweight Local-Mixer and Global-Mixer modules to align and integrate these features with the temporal input, and reports superior performance across diverse benchmarks with strong few-shot and zero-shot generalization at low computational cost.

Significance. If the layer-wise specialization finding proves robust to changes in tokenization, patching, and model family, and the mixer modules demonstrably leverage it, the approach could meaningfully improve utilization of hierarchical LLM representations for multi-scale time series tasks, offering a lightweight alternative to both pure Transformer and black-box LLM baselines.

major comments (2)
  1. [Abstract] Abstract: the load-bearing empirical claim that shallow LLM layers capture local dynamics while deeper layers encode global trends is stated without reference to controls for input representation, patching scheme, or LLM choice; if the observed specialization is an artifact of the specific tokenization or datasets used for probing, the performance advantage over prior final-layer baselines is not explained by the stated mechanism.
  2. [Method] Method section (Local-Mixer and Global-Mixer description): the modules are introduced to align features across layers, yet no ablation isolates their contribution versus simpler concatenation or attention-based fusion; without such controls, it remains unclear whether the reported gains require the full proposed architecture or could be achieved by routing any multi-layer features through a single mixer.
minor comments (1)
  1. [Abstract] Abstract: the phrase 'extensive experiments demonstrate' would benefit from a one-sentence summary of the benchmark datasets, number of baselines, and primary metrics to allow readers to gauge scope immediately.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We are grateful to the referee for the constructive feedback. We address each major comment below and have incorporated revisions to strengthen the manuscript.

read point-by-point responses
  1. Referee: [Abstract] Abstract: the load-bearing empirical claim that shallow LLM layers capture local dynamics while deeper layers encode global trends is stated without reference to controls for input representation, patching scheme, or LLM choice; if the observed specialization is an artifact of the specific tokenization or datasets used for probing, the performance advantage over prior final-layer baselines is not explained by the stated mechanism.

    Authors: We thank the referee for this observation. The original empirical analysis was conducted under the standard patching and tokenization of the benchmarks using Llama-2. To address robustness concerns, the revised manuscript now includes additional experiments (new Section 4.3 and Appendix C) that vary patching schemes, input representations, and LLM families (including Llama-3 and Mistral). These controls confirm the shallow-local and deep-global specialization persists, supporting that the gains over final-layer baselines arise from the proposed mechanism rather than setup-specific artifacts. The abstract has been updated to reference these controls. revision: yes

  2. Referee: [Method] Method section (Local-Mixer and Global-Mixer description): the modules are introduced to align features across layers, yet no ablation isolates their contribution versus simpler concatenation or attention-based fusion; without such controls, it remains unclear whether the reported gains require the full proposed architecture or could be achieved by routing any multi-layer features through a single mixer.

    Authors: We agree that isolating the mixers' contribution is important. The revised manuscript adds an ablation study (Section 5.2) comparing Logo-LLM against variants using direct multi-layer concatenation and a single attention-based fusion module in place of the separate Local-Mixer and Global-Mixer. Results show the specialized mixers yield further accuracy gains, especially in few-shot settings, indicating the design is not interchangeable with simpler fusion. The method section has been clarified to explain the rationale for separate local and global alignment. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected in derivation or claims

full rationale

The paper's central elements consist of an empirical observation on LLM layer representations for time series (shallow layers for local dynamics, deeper for global trends), followed by introduction of Local-Mixer and Global-Mixer modules to exploit this, and validation via benchmark experiments including few-shot and zero-shot settings. No equations are presented that reduce a claimed prediction or result to fitted inputs or self-definitions by construction. The architecture is motivated by the stated empirical analysis rather than redefining quantities circularly, and no load-bearing self-citations or uniqueness theorems from prior author work are invoked in the provided text. Performance superiority is asserted based on experimental outcomes, which remain externally falsifiable and independent of the design rationale itself.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 2 invented entities

The central design rests on an empirical observation about LLM layer semantics and introduces two new mixer modules whose value is justified only by the paper's own experiments.

axioms (1)
  • domain assumption Shallow layers of LLMs capture local dynamics in time series, while deeper layers encode global trends.
    This premise is invoked to justify the multi-layer extraction strategy and is presented as shown through empirical analysis.
invented entities (2)
  • Local-Mixer module no independent evidence
    purpose: Align and integrate local features from shallow LLM layers with the temporal input
    New lightweight component introduced to handle short-term patterns.
  • Global-Mixer module no independent evidence
    purpose: Align and integrate global features from deeper LLM layers with the temporal input
    New lightweight component introduced to handle long-term trends.

pith-pipeline@v0.9.0 · 5713 in / 1336 out tokens · 83214 ms · 2026-05-22T15:12:23.176458+00:00 · methodology

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Reference graph

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