Diffusion and Score-Based Generative Models

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Yang Song, Stanford University

Generating data with complex patterns, such as images, audio, and molecular structures, requires fitting very flexible statistical models to the data distribution. Even in the age of deep neural networks, building such models is difficult because they typically require an intractable normalization procedure to represent a probability distribution. To address this challenge, we consider modeling the vector field of gradients of the data distribution (known as the score function), which does not require normalization and therefore can take full advantage of the flexibility of deep neural networks. I will show how to (1) estimate the score function from data with flexible deep neural networks and efficient statistical methods, (2) generate new data using stochastic differential equations and Markov chain Monte Carlo, and even (3) evaluate probability values accurately as in a traditional statistical model. The resulting method, called score-based generative modeling or diffusion modeling, achieves record performance in applications including image synthesis, text-to-speech generation, time series prediction, and point cloud generation, challenging the long-time dominance of generative adversarial networks (GANs) on many of these tasks. Furthermore, score-based generative models are particularly suitable for Bayesian reasoning tasks such as solving ill-posed inverse problems, yielding superior performance on several tasks in medical image reconstruction.
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recommended to anyone who wants to understand beyond the mere "noising/denoising" type explanations on diffusion models

Blueshockful
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This one of the best presentations I have ever attended

moaidali
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What an amazing explanation. Wish there was an AI/authors explaining their papers so clearly.

opinions
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Thank you guys for making this talk available on your YouTube channel. This is pure gold

StratosFair
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It really shows how good the explanation is when even I can follow along. Thanks for sharing!

jacksonyan
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This is the best summarizing resource I have found on the topic. The visual aids are really helpful and the nature of the problem and series of steps leading to improved models, along with the sequence of logic are so clear. What an inspiration!

simong
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9:52 intractable to compute integral of exponential of neural networks
12:00 desiderata of deep generative models
19:00 the goal is to minimize fisher divergence between \nabla_x log(p(x_data)) and score function s(x), we don't know ground truth log(p(x_data)) but score matching is equivalent to fisher divergence up to the constant, thus same in the optimization perspective.
23:00 however, score matching is not scalable, greatly due to the Jacovian term. the term requires many times of backpropagation computations. Thus before computing fisher divergence, project each terms with vector v to make the Jacobian disappear, and thus become more scalable, this is called sliced score matching.
29:00 denoised score matching. The objective is tractable because we design the perturbation kernel by hand(the kernel is easily computable). However because of added noise, the denoised score matching can't estimate noise free distributions. Also the variance of denoising score matching objective becomes bigger and bigger eventually explodes when the smaller the magnitude of the noise.
31:20 in case of Gaussian perturbation kernel, denoising score matching problem takes more simpler form. Optimize the objective with stochastic gradient descent. Be careful to choose appropriate magnitude of sigma.
36:00 sampling from langevin dynamics, initialize x0 from simple(gaussian, uniform) distribution and z from N(0, 1), and then repeat the procedure.
37:20 naive version of langevin dynamics sampling not working well in practice because of the low density region

김인수-zp
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Amazing insights into generative models! Thanks for sharing this valuable knowledge!

LifeCodeGame
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16:54 all papers referenced... This man is amazing

CohenSu
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What a pleasant insight to think of gradients of the logits as score function! Thank you for sharing the great idea.

binjianxin
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Very clear! Thanks for this amazing lecture!

xiaotongxu
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Really amazing explanation for the entire diffusion model. Clear, great, wonderful work.

xuezhixie
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Extremely insightful lecture that is worth every minute of it. Thanks for sharing it.

ck
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khatarnaak aadmi hain !!
Very good explanation !!!
sab ka saath, sab ka vikaas

coolguy
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a very accessible and amazing tutorial that explained everything clearly and thoroughly!

peterpan
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I love this talk! amazing and clear explanation!

mm_Tesla_mm
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46:30 was a true mic-drop moment from Yang Song 😄

YashBhalgat
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I am 44 second in the talk and already wanna say thank you! :)

johnini
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Amazing explation for me to understand the diffusion model!

hasesukkt
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Such an incredible talk, i was just curious about how everyone here keeps track of all this knowledge, would love to hear from you all

dy