BitDelta: Your Fine-Tune May Only Be Worth One Bit
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Abstract (arXiv)
Large Language Models (LLMs) are typically trained in two phases: pre-training on large internet-scale datasets, and fine-tuning for downstream tasks. Given the higher computational demand of pre-training, it's intuitive to assume that fine-tuning adds less new information to the model, and is thus more compressible. We explore this assumption by decomposing the weights of fine-tuned models into their pre-trained components and an additional delta. We introduce a simple method, BitDelta, which successfully quantizes this delta down to 1 bit without compromising performance. This interesting finding not only highlights the potential redundancy of information added during fine-tuning, but also has significant implications for the multi-tenant serving and multi-tenant storage of fine-tuned models. By enabling the use of a single high-precision base model accompanied by multiple 1-bit deltas, BitDelta dramatically reduces GPU memory requirements by more than 10x, which can also be translated to enhanced generation latency in multi-tenant settings. We validate BitDelta through experiments across Llama-2 and Mistral model families, and on models up to 70B parameters, showcasing minimal performance degradation over all tested settings.
Key facts. Cited by 39 papers in the map (data through 14 Oct 2026). Builds on 40 of its 62 references that are in the map. First posted on arXiv 15 Feb 2024.
Builds on
40 of 62 references.
References · 40
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Citing papers per year: 2024: 15; 2025: 13; 2026: 11.
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- 2025Seeing Delta Parameters as JPEG Images: Data-Free Delta Compression with Discrete Cosine Transform9 Mar 2025
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- 2026Signs Beat Floats: Low-Rank Double-Binary Adaptation for On-Device Fine-Tuning22 May 2026
- 2026Skill Weaving: Efficient LLM Improvement via Modular Skillpacks21 May 2026
- 2026Dynamic Model Merging Made Slim17 May 2026
- 2026Auto-FlexSwitch: Efficient Dynamic Model Merging via Learnable Task Vector Compression30 Apr 2026
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- 2026D-QRELO: Training- and Data-Free Delta Compression for Large Language Models via Quantization and Residual Low-Rank Approximation18 Apr 2026
- 2026SOLAR: Communication-Efficient Model Adaptation via Subspace-Oriented Latent Adapter Reparametrization9 Apr 2026
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