Deep Unsupervised Learning using Nonequilibrium Thermodynamics
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive license to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/1503.03585
Summary
Probabilistic models usually force a trade-off. Simple distributions are easy to fit and evaluate but miss rich structure. Expressive ones need intractable normalization constants and expensive Monte Carlo sampling. The authors draw on non-equilibrium statistical physics and annealed importance sampling to get both properties. A fixed forward Markov chain adds small amounts of Gaussian (or binomial) noise over many steps until the data becomes a simple, tractable distribution. A generative model is then trained to undo this corruption one step at a time. When steps are small, each reversal has the same functional form as the forward kernel, so learning only requires estimating per-step means and covariances (or bit-flip rates), optimized through a lower bound on log likelihood. The resulting model, with thousands of time steps, supports exact sampling, cheap probability evaluation and straightforward posterior computation, for example in denoising and inpainting. Experiments cover a 2-D swiss roll, binary sequences, MNIST, CIFAR-10, bark textures and dead leaves images. The work laid the foundation for later diffusion-based generative models.
Key points
- Framework. Generation runs a learned reverse diffusion from an identity-covariance Gaussian (or independent binomial) back to the data. The model is defined as the endpoint of this chain, so its probabilities can be evaluated analytically.
- Dead leaves. The model reaches state-of-the-art performance with a log-likelihood bound of 1.489 bits/pixel, compared with 1.244 bits/pixel for MCGSM (Theis et al., 2012).
- MNIST. Parzen-window estimates using the code from Goodfellow et al. (2014) give 317 ± 2.7 bits. This is comparable to the Deep GSN (309), adversarial net (325) and DBN (199); a "perfect model" scores 349.
- Binary heartbeat (length-20 sequences). Learning is nearly perfect: the bound is −2.414 bits/seq versus the true −2.322 bits/seq. On CIFAR-10, the bound improves on the Gaussian baseline by 11.5 ± 0.2 bits/pixel.
- Implementation. An open-source reference implementation built on Blocks and trained with RMSprop is available at github.com/Sohl-Dickstein/Diffusion-Probabilistic-Models. The paper was presented at ICML 2015.
Cited by
- Structured Denoising Diffusion Models in Discrete State-Spaces
- On the Opportunities and Risks of Foundation Models
- Parameter-Efficient Fine-Tuning for Large Models: A Comprehensive Survey
- Classifier-Free Diffusion Guidance
- Diffusion-LM Improves Controllable Text Generation
- Flow Matching for Generative Modeling
- The AI Scientist: Towards Fully Automated Open-Ended Scientific Discovery
- Large Language Diffusion Models
- SDXL: Improving Latent Diffusion Models for High-Resolution Image Synthesis
- Unsupervised Representation Learning with Deep Convolutional Generative Adversarial Networks
- Hierarchical Text-Conditional Image Generation with CLIP Latents
- Photorealistic Text-to-Image Diffusion Models with Deep Language Understanding
- Generative Modeling by Estimating Gradients of the Data Distribution
- Denoising Diffusion Implicit Models
- Score-Based Generative Modeling through Stochastic Differential Equations
Cite
@misc{sohldickstein2015deep,
title = {{Deep Unsupervised Learning using Nonequilibrium Thermodynamics}},
author = {Sohl-Dickstein, Jascha and Weiss, Eric A. and Maheswaranathan, Niru and Ganguli, Surya},
year = {2015},
doi = {10.48550/arxiv.1503.03585},
eprint = {1503.03585},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.1503.03585}
}References
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