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NOLA: Compressing LoRA using Linear Combination of Random Basis
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Proposes NOLA, which reparameterizes LoRA's low-rank factors as linear combinations of frozen random basis matrices and trains only the mixture coefficients, breaking LoRA's rank-one parameter floor.
Problem
LoRA's parameter count is lower-bounded by rank one and is tied to layer shape and rank, limiting compression when storing many task-specific fine-tuned LLMs.
Approach
Re-parameterize LoRA's A and B matrices as linear combinations of pseudo-random fixed basis matrices (seeded), optimizing only the mixture coefficients; this decouples trainable parameter count from rank and layer dimensions, and allows coefficients to be quantized to 4 bits.
Key results
- On E2E with GPT-2 L, NOLA with 0.036M trainable parameters reaches BLEU 70.1, versus 70.4 for LoRA rank 4 with 0.77M parameters (about 20x fewer).
- On LLaMA-2 70B (8-bit), NOLA uses 0.57M trainable parameters (95% reduction vs rank-one LoRA at 12.94M) with MMLU 69.4 vs 69.5 for LoRA.
- NOLA with 3-bit quantization-aware training on GPT-2 L loses only ~0.3 BLEU (70.14) while LoRA rank 1 drops ~2.8 BLEU (67.08).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Replace LoRA rank 4 with NOLA QV using 0.036M parameters | GPT-2 L · E2E NLG Challenge | BLEU: 70.4 -> 70.1 | No clear effect |
| Share the random basis across layers (ablation) | NOLA QV · E2E NLG Challenge | BLEU: 70.46 -> 70.32 | No clear effect |
| Use rank 2 instead of rank 8 (ablation) | NOLA QV on GPT-2 M · E2E NLG Challenge | BLEU: 70.03 -> 70.47 | Helped |
| Use rank 1 instead of rank 8 (ablation) | NOLA QV on GPT-2 M · E2E NLG Challenge | BLEU: 70.03 -> 69.09 | Hurt |
| Reduce trainable parameters from 96K to 48K (ablation) | NOLA QV on GPT-2 M · E2E NLG Challenge | BLEU: 70.03 -> 70.09 | No clear effect |
| Reduce trainable parameters from 96K to 24K (ablation) | NOLA QV on GPT-2 M · E2E NLG Challenge | BLEU: 70.03 -> 68.30 | Hurt |
| Quantize coefficients to 4-bit after training (ablation) | NOLA QV on GPT-2 L · E2E NLG Challenge | BLEU: 70.46 -> 70.29 | No clear effect |
| Use 3-bit quantization-aware training instead of full precision (ablation) | NOLA QV on GPT-2 L · E2E NLG Challenge | BLEU: 70.46 -> 70.14 | No clear effect |
| Use 2-bit quantization-aware training (ablation) | NOLA QV on GPT-2 L · E2E NLG Challenge | BLEU: 70.46 -> 68.69 | Hurt |
| Apply NOLA to MLP layers rather than QV attention projections (ablation) | ViT-L NOLA · CIFAR-100 5-shot | accuracy: 74.8 -> 75.1 | Helped |
| Apply NOLA to MLP layers with 0.047M parameters instead of LoRA rank 4 | ViT-B · Food101 5-shot | accuracy: 60.8 (1.6) -> 64.5 (0.8) | Helped |
| Use NOLA rather than PRANC | ResNet18 · ImageNet-100 | accuracy: 61.08% -> 64.66% | Helped |
Surprising findings
- NOLA with rank 8 at equal parameter count is reported as matching or beating LoRA, and the paper notes that rank had little effect on NOLA performance when parameter count is held fixed.
Limitations
- Trainable-parameter savings do not reduce inference-time compute, and the paper states it does not claim accuracy gains over baselines.
- Effect of rank is not rigorously studied and is left as future work.
- Non-shared random basis is slightly slower than LoRA in training time.
Experimental setup
Datasets: E2E NLG Challenge DART WebNLG Alpaca MMLU CIFAR-10 CIFAR-100 CUB-200-2011 Caltech-101 Aircraft Food101 Pets
Benchmarks: E2E NLG Challenge DART WebNLG Alpaca MMLU CIFAR-10 CIFAR-100 CUB-200-2011 Caltech-101 Aircraft Food101 Pets
Metrics: BLEU NIST METEOR ROUGE-L CIDEr TER training loss validation loss MMLU accuracy top-1 accuracy
Baselines: LoRA Adapter PreLayer Full fine-tuning QLoRA PRANC HashedNet Linear probe Nearest neighbor
Builds on: LoRA PRANC QLoRA Straight-Through Estimator
Closest papers by meaning
- Uni-LoRA: One Vector is All You Need (NeurIPS 2025 · similarity 0.93)
- Dynamic Low-Rank Sparse Adaptation for Large Language Models (ICLR 2025 · similarity 0.92)
- Train Small, Infer Large: Memory-Efficient LoRA Training for Large Language Models (ICLR 2025 · similarity 0.91)
- BSLoRA: Enhancing the Parameter Efficiency of LoRA with Intra-Layer and Inter-Layer Sharing (ICML 2025 · similarity 0.91)
- Merging LoRAs like Playing LEGO: Pushing the Modularity of LoRA to Extremes Through Rank-Wise Clustering (ICLR 2025 · similarity 0.91)
- Flat-LoRA: Low-Rank Adaptation over a Flat Loss Landscape (ICML 2025 · similarity 0.91)
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