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While I think I agree that there are many posts here on HackerNews announcing a new model compression technique, your characterization above understates the tec
by ttul 2y ago
While I think I agree that there are many posts here on HackerNews announcing a new model compression technique, your characterization above understates the technical innovations and practical impacts described in this MIT paper.
Unlike traditional model compression work that simply applies existing techniques, SVDQuant synthesizes several ideas in a comprehensive new approach to model quantization:
- Developing a novel outlier absorption mechanism using low-rank decomposition — this aspect alone seems quite novel, although the math is admittedly way beyond my level
- Combining SVD with smoothing in a way that specifically
addresses the unique challenges of diffusion models
- Creating an innovative kernel fusion technique (they call it “Nunchaku”) that makes the theoretical benefits practically realizable, because without this, the extra computation required to implement the above steps would simply slow the model back down to baseline
This isn't just incremental improvement - the paper achieves several breakthrough results:
- First successful 4-bit quantization of both weights AND activations for diffusion models
- 3.5x memory reduction for 12B parameter models while maintaining image quality
- 3.0x speedup over existing 4-bit weight-only quantization approaches
- Enables running 12B parameter models on consumer GPUs that previously couldn't handle them
And, I’ll add, as someone who has been following the diffusion space quite actively for the last two years, the amount of creativity that can be unleashed when models are accessible to people with consumer GPUs is nothing short of astonishing.
The authors took pains to validate their approach by testing it against three models (Flux, PixArt-Sigma, and SDXL) and along several quality-comparison axes (FID score, Image Reward, LPIPS, and PSNR). They also did a proper ablation study to see the contribution of each component in their approach to image quality.
What particularly excites me about this paper is not the ability to run a model that eats 22GB of VRAM in just 7GB. The exciting thing is the prospect of running a 60GB model in 20GB of VRAM. I’m not sure whether anyone has or is planning to train such a monster, but I suspect that Midjourney, OpenAI, and Google all have significantly larger models running in their infrastructure than what can be run on consumer hardware. The more dimensions you can throw at image and video generation, the better things get.
- djoldman 2y agoI definitely agree that there may be some interesting advancements here. I am trying to call attention to the models used for evaluation comparison. There are 3 factors: inference speed/latency, model size in total loaded VRAM, and model performance in terms of output. Comparisons should address all of these considerations, otherwise it's easy to hide deficiencies.
- Jackson__ 2y agoThe site literally has a quick visual comparison near the top, which shows that theirs is the closest to 16bit performance compared to the others. I don't get what more you'd want. https://cdn.prod.website-files.com/64f4e81394e25710d22d042e/672d1bcef3c3ec127e8078fd_672d1b2115081c1e8ac82ea9_teaser.jpeg https://cdn.prod.website-files.com/64f4e81394e25710d22d042e/...
- djoldman 2y agoThese are comparisons to other quantizing methods. That is fine. What I want to see is comparisons to NON-quantized models all with around the same VRAM along with associated inference latencies. Also, we would want to see the same quantizing schemes applied to other base models.. because perhaps the paper's proposed quantizing scheme only beats others using a particular base model.
- snovv_crash 2y agoThey tested the quantisation on 3 different models. They also show it has little to no effect relative to fp16 on these models. IMO that's enough. Comparison against smaller models is much less useful because you can't use the same random seeds. So you end up with a very objective "this is worse" based purely on aesthetic preferences of one person vs another. You already see this with Flux Schnell vs. the larger Flux models.
- djoldman 2y agoI disagree. They report that their method produces a model that is 6.5 GB from flux (22.7GB). Why wouldn't you want to know how their 6.5GB model compares to other 6.5GB models? Regarding aesthetic prefs: it's an open problem what an appropriate metric is for GenAI... LLM arena is widely regarded as a good way to measure LLMs and that's user preferences. In any case, the authors report LPIPs etc. They could do the same for other small models.
- 2y ago