lora-lite

Hackable PyTorch adapters for LoRA-family and small PEFT experiments.

Hackable code

To keep it simple and hackable we make these choices:

• Simple forward hooks, no module replacement or custom modules.
• Simple code over fast performance
• No merge/unmerge
• Single test where we train on MetaMathQA and test on GSM8K for each variant

Take a look at lora.py

Install

pip install -e git+https://github.com/wassname/lora-lite.git#egg=lora-lite

Quickstart

import torch, lora_lite as ll

model = MyTransformer()
cfg = ll.LoRAConfig(r=8, alpha=16, dtype=torch.bfloat16)
ll.attach(model, cfg)

opt = torch.optim.AdamW([p for p in model.parameters() if p.requires_grad], lr=1e-4)
# train...

ll.save(model, "adapter.safetensors")
ll.detach(model)
ll.load(model, "adapter.safetensors")

Does it work?

just check       # pytest + smoke + package build + metadata check
just bnb-smoke   # required CUDA bitsandbytes 4bit/8bit smoke
just qwen-probe  # Qwen/Qwen3-0.6B train/save-load probe

Variants

Variant	4bit/8bit	GSM8K %	Params	Peak GPU (GB)
LoRA	yes	63.2%	4.59M	11.3
PiSSA	no	63.2%	4.59M	11.3
DoRA	no	62.4%	4.67M	11.3
DeLoRA	yes	61.5%	4.59M	11.3
AntiPaSTO	no	61.4%	14.3K	11.3
IA3-FF	yes	61.4%	86K	11.4
EVA	no	60.3%	4.59M	11.3
IA3	yes	60.0%	57K	11.4
HRA	yes	61.6%	1.84M	11.3

Params = trainable adapter params. Peak GPU = peak CUDA memory during train+eval (logged from this run onward; older runs predate the column).

Setup: Qwen3-0.6B-Base, MetaMathQA train (5k steps, batch 4 = 20k samples unless noted), r=32, all q/v targets, GSM8K test (1319 examples). HRA used batch 2 (10k samples) due to memory. The AntiPaSTO family used r=256 (default for these variants).

Reference: PEFT reports LoRA at 49.0% on Llama-3.2-3B (different model, different sample count). Our numbers are not directly comparable but suggest the adapters work.

AntiPaSTO family

AntiPaSTO learns a per-direction gain on the frozen top-r SVD basis (S_eff = S * (1 + ELU(coeff*g))), so it rescales existing singular directions rather than creating new ones, hence ~320x fewer trainable params than LoRA at ~97% of its accuracy. All variants share the diagonal gain; they differ only in the basis they steer in or the extra structure on the top directions. All have base_grad_leaks=0 (the frozen residual weight gets no gradient).

Variant	GSM8K %	Params	Basis / extra structure
antipasto_corda	61.9%	14.3K	covariance-oriented input projector P = Vh·C^{-1/2} (best of family)
antipasto	61.4%	14.3K	plain weight-SVD basis, diagonal gain only
antipasto_rot	61.4%	35.8K	+ block-Cayley rotation of the basis (the version this replaces)
antipasto_ablate	61.0%	14.4K	contractive output ablation (I - α ĉĉᵀ)diag(S), can't amplify
antipasto_arrow	60.5%	17.5K	dense b×b mixing block on the top-b directions + diagonal tail

The rotation buys nothing here: antipasto_rot matches plain antipasto to 3 s.f. (61.4%) at 2.5x the params and +20% wall-time, while paying a per-forward Cayley solve. Dropping it (the current default) is free. CorDA's data-oriented basis is the only structure that helps on this capability task; the ablation/arrow cores are aimed at steering and suppression, where the diagonal-only basis can't reach off-axis behavior, so they don't pay off for raw GSM8K accuracy.

Developer docs

See docs/developer_guide.md for the variant API, data-calibrated init, and save/load format.

Citation

@misc{wassname2026loralite,
  title = {LoRA-Lite: A Hackable Adapter Library for Research},
  author = {Michael J. Clark},
  year = {2026},
  url = {https://github.com/wassname/lora-lite/}
}