In plain words: They tested Transformer calculations on a light-based chip in small experiments, then used those results in simulations to measure energy use. Because energy per calculation drops as the model gets wider, big optical systems could be 100 times more efficient than today's digital chips.
Abstract
The rapidly increasing size of deep-learning models has caused renewed and growing interest in alternatives to digital computers to dramatically reduce the energy cost of running state-of-the-art neural networks. Optical matrix-vector multipliers are best suited to performing computations with very large operands, which suggests that large Transformer models could be a good target for optical computing. To test this idea, we performed small-scale optical experiments with a prototype accelerator to demonstrate that Transformer operations can run on optical hardware despite noise and errors. Using simulations, validated by our experiments, we then explored the energy efficiency of optical implementations of Transformers and identified scaling laws for model performance with respect to optical energy usage. We found that the optical energy per multiply-accumulate (MAC) scales as $\frac{1}{d}$ where $d$ is the Transformer width, an asymptotic advantage over digital systems. We conclude that with well-engineered, large-scale optical hardware, it may be possible to achieve a $100 \times$ energy-efficiency advantage for running some of the largest current Transformer models, and that if both the models and the optical hardware are scaled to the quadrillion-parameter regime, optical computers could have a $>8,000\times$ energy-efficiency advantage over state-of-the-art digital-electronic processors that achieve 300 fJ/MAC. We analyzed how these results motivate and inform the construction of future optical accelerators along with optics-amenable deep-learning approaches. With assumptions about future improvements to electronics and Transformer quantization techniques (5$\times$ cheaper memory access, double the digital--analog conversion efficiency, and 4-bit precision), we estimated that optical computers' advantage against current 300-fJ/MAC digital processors could grow to $>100,000\times$.
Maxwell G. Anderson, Shi-Yuan Ma, Tianyu Wang, Logan G. Wright, Peter L. McMahon
arXiv:2302.10360 · cs.ET, cs.LG, cs.NE, physics.app-ph, physics.optics · submitted Feb 20, 2023
abstract · pdf · html · 27 pages, 13 figures
Running the math on a machine with 8x A100 (enough to run today's LLMs), that would be 300w * 8gpus / 100 = 24w.
This is within striking distance of IOT and personal devices. I'm trying to imagine what a world would look like where generative text models are commodetised to the point where you can either generate text locally on your phone, or generate GBs of text in the cloud.
I have to admit it's very hard to make any sort of accurate prediction.