Why Deep Learning Works So Well 🤖

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New Patreon Rewards 33:31- own a piece of Welch Labs history!
https://www.patreon.com/welchlabs

Books & Posters
https://www.welchlabs.com/resources

Sections
0:00 - Intro
4:49 - How Incogni Saves Me Time
6:32 - Part 2 Recap
8:10 - Moving to Two Layers
9:15 - How Activation Functions Fold Space
11:45 - Numerical Walkthrough
13:42 - Universal Approximation Theorem
15:45 - The Geometry of Backpropagation
19:52 - The Geometry of Depth
24:27 - Exponentially Better?
30:23 - Neural Networks Demystifed
31:50 - The Time I Quit YouTube
33:31 - New Patreon Rewards!

Special Thanks to Patrons https://www.patreon.com/welchlabs
Juan Benet, Ross Hanson, Yan Babitski, AJ Englehardt, Alvin Khaled, Eduardo Barraza, Hitoshi Yamauchi, Jaewon Jung, Mrgoodlight, Shinichi Hayashi, Sid Sarasvati, Dominic Beaumont, Shannon Prater, Ubiquity Ventures, Matias Forti, Brian Henry, Tim Palade, Petar Vecutin, Nicolas baumann, Jason Singh, Robert Riley, vornska, Barry Silverman, Jake Ehrlich, Mitch Jacobs, Lauren Steely, Jeff Eastman, Rodolfo Ibarra, Clark Barrus, Rob Napier, Andrew White, Richard B Johnston, abhiteja mandava, Burt Humburg, Kevin Mitchell, Daniel Sanchez, Ferdie Wang, Tripp Hill, Richard Harbaugh Jr, Prasad Raje, Kalle Aaltonen, Midori Switch Hound, Zach Wilson, Chris Seltzer, Ven Popov, Hunter Nelson, Amit Bueno, Scott Olsen, Johan Rimez, Shehryar Saroya, Tyler Christensen, Beckett Madden-Woods, Darrell Thomas, Javier Soto

References
Simon Prince, Understanding Deep Learning. https://udlbook.github.io/udlbook/
Liang, Shiyu, and Rayadurgam Srikant. "Why deep neural networks for function approximation?." arXiv preprint arXiv:1610.04161 (2016).
Hanin, Boris, and David Rolnick. "Deep relu networks have surprisingly few activation patterns." *Advances in neural information processing systems* 32 (2019).
Hanin, Boris, and David Rolnick. "Complexity of linear regions in deep networks." *International Conference on Machine Learning*. PMLR, 2019.
Fan, Feng-Lei, et al. "Deep relu networks have surprisingly simple polytopes." *arXiv preprint arXiv:2305.09145* (2023).

All Code:
https://github.com/stephencwelch/manim_videos

100k neuron wide example training code: https://github.com/stephencwelch/manim_videos/blob/master/_2025/backprop_3/notebooks/Wide%20Training%20Example.ipynb

Written by: Stephen Welch
Produced by: Stephen Welch, Sam Baskin, and Pranav Gundu

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