How LLMs work(0xkato.xyz) |
How LLMs work(0xkato.xyz) |
This is to say: the autoregressive decoder-only transformer llm architecture as pioneered by openai is wildly simple for how revolutionary its results are. I was reading about non-learned classical SLAM systems (uses video + handcrafted math to produce 3d mappings of physical spaces while also locating the camera in those spaces) at the time, and comparatively speaking I’d say the math is about as complicated as ONE of the components in those complex formulations. The only reason frontier LLMs need 6-figure computers to run is because the model designers made the middle bit in those models REALLY BIG, dimensionally speaking. They just took the steam engine, made a few gargantuan versions of it, and are selling them as the ultimate source of power.
This was openai’s entire breakthrough. Making this particular model architecture larger leads to emergent capabilities like being able to pick the best ending to a story/set of instructions or answer questions about broad factual knowledge. I’ve been meanwhile watching these AI companies attempt, successfully, to sell this capability as some sort of robot consciousness hand-crafted by supergeniuses. The fact that they are getting away with it is almost as shocking to me as the discovery itself.
Language Models are Few-Shot Learners https://arxiv.org/abs/2005.14165
I also enjoyed the papers for DeepSeek and GLM for an overview of all the tricks you need to make these things work
DeepSeek-V3.2: Pushing the Frontier of Open Large Language Models https://arxiv.org/abs/2512.02556
GLM-4.5: Agentic, Reasoning, and Coding (ARC) Foundation Models https://arxiv.org/abs/2508.06471
I have to wonder though. Is this all a human brain is? A similar thing to an LLM just scaled exponentially larger. I mean a brain is not just neurons with simple connections to each other. The neurons, axons, dendrites, <insert_unexplained_thing>, etc in a brain are all holding and processing information in different ways and doing it nearly 100% in parallel. That's a really big model.
The biological discoveries show how complex a biological brain actually is. Even the tiny brains in a bee or spider are able to solve puzzles and use tools. That's crazy.
No, it's not. There are many animals that have extremely complex and even learned behaviour that have literally zero neurons.
Clearly "neurons" is an oversimplification just-so story, not a scientific theory.
The secret sauce though is all the datasets, RL training, knowledge of what works from doing all kinds of ablation experiments, and a massive compute moat.
Tangentially related: This part always seemed fuzzy to me, especially when dealing with data scientists and how they talk about how 'ML' looks at problems. I had this issue when working at a SIEM vendor where they kept going on about use case development having to be designed a certain way to catch things. It was all very frustrating.
We still don’t really know why they work, we just know how to build them.
Good article, but when sharing it I will have to preface "yes it's slop, but it's a good explanation".
Absolutely embarrassing that the author didn't catch that these LLM-isms are a (and here I'll use one) bad signal.
In fact, I would go so far as to say that publishing in this style stems from a lack of reading experience and writing experience, which does not bode well for someone pretending to be an expert. I gave this article to someone highly intelligent who doesn't know the first thing about how LLMs work internally, and she immediately called out that it reads like AI text.
I've noticed the same thing is possible if you watch the output of a slow LLM. Eventually you start to see the machinery. input tokens = output tokens, it's math. I can't exactly predict the tokens generated but I can see how they are formed. It's a lot like chess. You can't see every possible move but the mechanism is understandable.
I can only imagine what sort of visualizations are going on today inside of the AI labs.
it goes all over the place.
i'm not actually sure who your target audience is.
there's too many side tangents.
just like, structure it plz.
1. customer feels bad cuz they don't understand how llms work
2. provide high level abstracted explanation (don't dive into concepts yet)
3. provide breakdown guide of overall set of components.
4. walk through each component. don't side track. no need to explain, ROPE,GQA etc... it just distracts.
i.e. customers don't know how llms work, leading them to feel bad about their own intelligence.
at a high level llms take in words, do some math on them, and then produce words, one by one.
inside llms have these different components. we walk through them step by step.
1. tokenizer
2. embedding
3. attention
4. heads
5. ffn
6. sampling
## tokenizer
I imagine if resources were spent writing this text then one benefit of using it is not using more resources or the pollution caused from a chatbot.
> Researchers have found that some neurons inside the FFN are strongly associated with specific concepts or facts. One neuron might activate strongly on Eiffel-Tower-related text. Another on programming languages. Another on past-tense verbs.
People don't really write like this and they don't really talk like this (and no, people don't necessarily write exactly how they talk because they don't read exactly how they listen; the written word can be backtracked while the heard cannot, and speakers/writers know this, either consciously or unconsciously). A person would probably structure this more like:
> Researchers have found that some neurons inside the FFN are strongly associated with specific concepts or facts. For example, there could be one neuron that activates strongly on Eiffel-Tower-related text, another that activates strongly on programming languages, a third neuron activating on past-tense verbs, and so on.
Usually people wouldn't write "Another on programming languages." as a standalone sentence like that because the periods introduce an unnatural pause like they're giving a TED talk, unless of course they were punctuating that way for effect, but you'd essentially never communicate with that effect full time.
https://www.youtube.com/watch?v=5MdSE-N0bxs is remarkably prescient given that it was written before LLMs
If we look beyond written languages which are late inventions of human civilization, oral languages are continuous and build with blocks not words.
Chomskyan school misled the entire field of linguistics for decades by ignoring spoken languages.
- V3 https://arxiv.org/abs/2412.19437
- V2 https://arxiv.org/abs/2405.04434
- R1 https://arxiv.org/abs/2501.12948 (RL applied to ML models was well-known beforehand, but they show it in the open, at scale, on big models)
Then, there's the incentive analysis. If you can see that these models empirically get better with scale, why would you swap the main architecture? Those events will be pretty rare. I'm not saying there's noone cooking a new architecture, just that it is a pretty rare event. And it would have to come from some researchers that would be happy to not publish their findings, which is not really what a sizable portion of elite researchers (obviously not all) are incentivized to do.
Of course, it's a bit of a verbal compression to claim simply 'scaled up'. They are recognisable scaled up transformers, but most new models come with a few tricks, but we're at the point where those usually are not an architectural rewrite and added to solve an explicit problem, like hallucination, not for big new capability gains.
My next child took a completely different path to language, including skipping all the non-verbal imitations.
And then at some point, you just suddenly can two-way communicate with them when you couldn't before, and then after that, they can engage in reasoning.
It’s interesting to me how similar attempting to understand LLMs is to neuroscience.
“When we turn this bit off, this other thing happens… if we change these weights the Eiffel Tower is now in Rome”
We’re basically just probing around and trying to reverse engineer an emergent system.
To your point, this system may be quite different from model to model (human to human) although some similarities likely occur.
The comment I was responding to tried to belittle the OP’s understanding of transformers, by mentioning that running an LLM at scale is much harder than the simple white board diagram.
My point was simply that we don’t know why they work, and all the extra optimizations isn’t the “thing” that makes it emergent.
Simply scaling the “GPT” is good enough to see it, so the OP’s awe should stand.
(On a side note, what other architectures can we scale to find similar emergent behavior?)
Adults are expected to have their world models approximately correct in terms of physical environment so they won’t accidentally kill themselves by falling off a cliff; then there are the social norms which adults are expected to conform to so everyone is kinda predictable to everyone else so adults don’t kill each other too often over food or mates. Understanding of neither is expected from children.
The "bitter lesson" is that fake-it-till-you-make-it is a valid way of doing knowledge work.
(Or not make it, then people will just claim you're holding the LLM wrong and it's not the AI's fault.)
Statistically most likely in what context, given which preconditions? Because each prompt sequence is unique so the probability of any token following it is unknown.