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No Task Left Behind: Isotropic Model Merging with Common and Task-Specific Subspaces

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arxiv 2502.04959 v3 pith:VJVXNYRZ submitted 2025-02-07 cs.LG

No Task Left Behind: Isotropic Model Merging with Common and Task-Specific Subspaces

classification cs.LG
keywords modelmergingperformancematricestask-specificalignmentmodelstask
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Model merging integrates the weights of multiple task-specific models into a single multi-task model. Despite recent interest in the problem, a significant performance gap between the combined and single-task models remains. In this paper, we investigate the key characteristics of task matrices -- weight update matrices applied to a pre-trained model -- that enable effective merging. We show that alignment between singular components of task-specific and merged matrices strongly correlates with performance improvement over the pre-trained model. Based on this, we propose an isotropic merging framework that flattens the singular value spectrum of task matrices, enhances alignment, and reduces the performance gap. Additionally, we incorporate both common and task-specific subspaces to further improve alignment and performance. Our proposed approach achieves state-of-the-art performance on vision and language tasks across various sets of tasks and model scales. This work advances the understanding of model merging dynamics, offering an effective methodology to merge models without requiring additional training. Code is available at https://github.com/danielm1405/iso-merging .

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Forward citations

Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. ResMerge: Residual-based Spectral Merging of Large Language Models

    cs.CL 2026-06 unverdicted novelty 7.0

    ResMerge improves merging of RL expert LLMs via a stable residual consensus backbone plus gated head correction, outperforming task-vector and spectral baselines in capability preservation.

  2. Hierarchical Semantic Correlation-Aware Masked Autoencoder for Unsupervised Audio-Visual Representation Learning

    cs.MM 2026-04 conditional novelty 6.5

    Localized Muon-style spectral orthogonalization of primary and constraint momentum subspaces (SIFT) reduces objective conflicts and improves constrained LLM steering across four tasks.

  3. DA-MergeLoRA: Hypernetwork-Based LoRA Merging for Few-Shot Test-Time Domain Adaptation

    cs.CV 2026-07 conditional novelty 6.0

    A hypernetwork generates per-column merging weights to combine source LoRA modules on CLIP, achieving state-of-the-art few-shot test-time domain adaptation.

  4. PACT: Preserving Anchored Cores in Task-vectors for Model Merging

    cs.LG 2026-06 unverdicted novelty 6.0

    PACT preserves load-bearing wall dimensions from pre-trained weights inside task vectors to reduce conflicts and improve merged model performance.

  5. PivotMerge: Bridging Heterogeneous Multimodal Pre-training via Post-Alignment Model Merging

    cs.CV 2026-04 unverdicted novelty 6.0

    PivotMerge merges heterogeneous multimodal pre-trained models via shared-space decomposition to filter conflicts and layer-wise weights based on alignment contributions, outperforming baselines on multimodal benchmarks.

  6. PivotMerge: Bridging Heterogeneous Multimodal Pre-training via Post-Alignment Model Merging

    cs.CV 2026-04 unverdicted novelty 6.0

    PivotMerge merges post-alignment cross-modal projectors from heterogeneous MLLM pre-training via shared-space filtering and layer-wise weights, beating prior merging baselines on multimodal benchmarks.

  7. Position: Zeroth-Order Optimization in Deep Learning Is Underexplored, Not Underpowered

    cs.LG 2026-05 unverdicted novelty 5.0

    Zeroth-order optimization is underexplored rather than underpowered in deep learning, with limitations stemming from full-space designs that can be addressed via subspace, spectral, and systems-aware approaches.