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GAN Math (2020)

GAN Math (2020)

19 comments

·August 28, 2025

staticelf

Reading an article like this makes me realize I am too stupid to ever build a foundation model from scratch.

oersted

Paper authors (and this posts author apparently) like to throw in lots of scary-looking maths to signal that they are smart and that what they are doing has merit. The Reinforcement Learning field is particularly notorious for doing this, but it's all over ML. Often it is not on purpose, everyone is taught this is the proper "formal" way to express these things, and that any other representation is not precise or appropriate in a scientific context.

In practice, when it comes down to code, even without higher-level libraries, it is surprisingly simple, concise and intuitive.

Most of the math elements used have quite straightforward properties and utility, but of course if you combine them all together into big expressions with lots of single-character variables, it's really hard to understand for everyone. You kind of need to learn to squint your eyes and understand the basic building-blocks that the maths represent, but that shouldn't be necessary if it wasn't obfuscated like this.

catgary

I’m going to push back on this a bit. I think a simpler explanation (or at least one that doesn’t involve projecting one’s own insecurities onto the authors) is that the people who write these papers are generally comfortable enough with mathematics that they don’t believe anything has been obfuscated. ML is a mathematical science and many people in ML were trained as physicists or mathematicians (I’m one of them). People write things this way because it makes symbolic manipulations easier and you can keep the full expression in your head; what you’re proposing would actually make it significantly harder to verify results in papers.

MattPalmer1086

Haha, recognise. I invented a fast search algorithm and worked with some academics to publish a paper on it last year.

They threw in all the complex math to the paper. I could not initially understand it at all despite inventing the damn algorithm!

Having said that, picking it apart and taking a little time with it, it actually wasn't that hard - but it sure looked scary and incomprehensible at first!

hoppp

It takes a while to get into, just like with everything determination is key

Also there are libraries that abstract away most if not all the things, so you don't have to know everything

staticelf

That's the thing, it's too hard to learn so I rather do something else with the limited time I have left.

gregorygoc

I come from a country which had a strong Soviet influence, and in school basically we were taught that behind every hard formula lies an intuitive explanation. As otherwise, there’s no way to come up with the formula in the first place.

This statement is not true, there are counter examples I encountered in my university studies but I would say that intuition will get you very far. Einstein was able to come up with special theory of relativity by just manipulating mental models after all. Only when he tried to generalize it, that’s when he hit the limit of the claim I learned in school.

That being said after abandoning intuition, relying on pure mathematical reasoning drives you to a desired place and from there you usually can reason about the theorem in an intuitive way again.

Math in this paper is not that hard to learn, you just need someone to present you the key idea.

reactordev

Haha, I was just going to say the same. I was hoping, I guess naively, that this would explain the math. Not just show me math. While I love a good figure, I like pseudocode just as much :)

colesantiago

Aren't GANs like ancient?

Last time I used a GAN was in 2015, still interesting to see a post about GANs now and then.

gchadwick

Whilst it's maybe not worth studying them in detail I'd say being aware of their existence and roughly how they work is still useful. Seeing the many varied ways people have done things with neural networks can be useful inspiration for your own ideas and perhaps the ideas and techniques behind GANs will find a new life or a new purpose.

Yes you can just concentrate on the latest models but if you want a better grounding in the field some understanding of the past is important. In particular reusing ideas from the past in a new way and/or with better software/hardware/datasets is a common source of new developments!

aDyslecticCrow

GAN is not a architecture its a training method. As the models themselves change underneath, GAN remain relevant. (Just as you see autoencoder still being used as a term in new published works, which is even older.)

Though if you can rephrase the problem into a diffusion it seems to be prefered these days. (Less prone to mode collapse)

Gan is famously used for generative usecases, but has wide uses for creating useful latent spaces with limited data, and show up in few-shot-learning-papers. (Im actually not that up to speed on the state of art in few-shot so mabie they have something clever that replace it)

radarsat1

Whenever someone says this I like to point out that they are very often used to train the VAE and VQVAE models that LDM models use. Slowly diffusion is encroaching on its territory with 1-step models, however, and there are now alternative methods to generate rich latent spaces and decoders too, so this is changing, but I'd say up until last year most of the image generators still used an adversarial objective for the encoder-decoder training. This year, not sure..

pilooch

Exactly, for real time applications VTO, simulators,...), i.e. 60+FPS, diffusion can't be used efficiently. The gap is still there afaik. One lead has been to distill DPM into GANs, not sure this works for GANs that are small enough for real time.

lukeinator42

they're also used a lot for training current TTS and audio codec models to output speech that sounds realistic.

sylos

The article is from 2020, so it would be closer to relevancy back then.

black_puppydog

Yeah, title needs (2020) added.

GANs were fun though. :)

GaggiX

Adversarial loss is still use on most image generators, diffusion/autoregressive models work on a latent space (they don't have to, but it would incredibly inefficient) created by an autoencoder, these autoencoders are trained on several losses, usually L1/L2, LPIPS and adversarial.

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