The research examined LoRA rank selection for diffusion model fine-tuning on CIFAR-10. The study utilized a DDPM U-Net with LoRA ranks of {2, 4, 8, 16, 32}. Optimization settings and a reproducible local-folder pytorch-fid protocol were fixed. The evaluation metrics included FID, trainable parameters, runtime, and GPU memory usage.
The results indicated that moderate LoRA ranks were most efficient. Specifically, a rank of 4 achieved the lowest DDPM FID (124.1380), while rank 8 was very close (124.2136). Higher ranks demonstrated limited gains in FID despite increased adaptation costs.
Extended-budget DDPM runs (20 epochs; ranks 4/8/16) and a Tiny DiT backbone (10 epochs; ranks 4/8/16) validated these trends. These findings suggest small-to-moderate LoRA ranks as practical defaults under fixed training budgets.