Top
Best
New

Posted by 0xkato 2 days ago

How LLMs work(www.0xkato.xyz)
680 points | 188 commentspage 2
whyage 5 hours ago|
Style nit: the transitions between dark-mode text and large diagrams with a snow white background are jarring.
AltruisticGapHN 10 hours ago||
I don't like how most LLM explainer articles and videos say that essentially a LLM " predicts the next word".

I'm a developer but not very good at maths and I still don't understand any of it.

A LLM clearly has some "visual" capacity. You ask Gemini to build something with Canvas and it's able to reason about the shape of things. Like recently I waanted a checkbox that has like a gradient flowing around the edge. It figured out it could use a radial gradient from the center of the checkbox, and overlay that with a small inner div so you only see the edge that looks like the gradient is circling around the checkbox.

How is that "predicting the next word"?

Not saying AI is intelligent or conscious or anything like that, but the algorithm clearly is far more complex than "predicting words".

What I mean, is the LLM is able to represent things in space . That part I don't understand.

I also still dont understand the relationship between the chat based LLM and the multi modal stuff. I think I read somewhere when image is generated it is also tokens?

dev_hugepages 10 hours ago||
Predicting a word is the final objective, as in the output of the model is a probability distribution of the next token. However, choosing the right token is more complicated than just regurgitating the training data (and you won't encounter an exact example in the training data, so you need to interpolate). This makes the model learn abstract representation of things that it is able to manipulate before outputting this back into token. RL also complicates this because the "fitness" is now some arbitrary metric computed over an entire sequence of tokens.
Borealid 10 hours ago|||
Your casual understanding is imprecise.

At all times the LLM is, indeed, predicting the next token. Anything it does emerges from that.

It did not "figure anything out". It predicted that text describing the use of a radial gradient was likely to follow text describing your problem.

hackinthebochs 5 hours ago|||
>At all times the LLM is, indeed, predicting the next token

The point is that saying they're just "predicting the next token" is not at all explanatory nor providing insight. Saying the brain is just firing action potentials gives you no understanding about how the brain does what it does or what the space of its capabilities are. Similarly, predicting the next token tells you nothing about the capabilities of LLMs.

layla5alive 8 hours ago|||
Lol, the bird did not 'fly' - it just flapped its wings and generated lift!
Borealid 5 hours ago|||
No. The how is relevant here because it leads to understanding of the resulting behavior.

If you train the LLM on a corpus that shows people saying the sky is red, you get an LLM that is predisposed to say the sky is red. This is true even if it's also trained on all of the science that explains how and why the sky is blue.

If it were to "figure out" or "reason", it would not have such a predisposition to emit "red" after "the sky is" just because that matches the reward during training.

In other words, the token prediction is important because it both explains the successes AND the failures of the LLM. If there were situations in which a bird could fail to fly, then how it tried to fly would also be crucial knowledge.

layla5alive 10 minutes ago||
You can also teach humans science and math and then they can be trained by a cult to not use any of that reasoning when emitting canned responses that they were rewarded by the cult for internalizing during their training. "Fake News!"

You're caught up on the mechanics of token processing (floating point matrix ALU math) and ignoring the context that p(next token) as a function being "computed" is doing so over a trillion parameters. You can poorly train a model, sure, but assuming you don't indoctrinate it too much, properties like cognition emerge - it learns to reason; why? Reasoning is more efficient and compact than memorizing answers.

qsera 8 hours ago|||
More like being suspended by a thread...
raincole 4 hours ago|||
> What I mean, is the LLM is able to represent things in space . That part I don't understand.

Why do you think this is mutually exclusive to "LLM predicts the next token"?

If you tell someone from 19th century that bytes (just 0s and 1s!) can represent an opera, a song, or even a whole interactive experience, they might be really confused. But there is no reason they can't.

If you tell someone without math background that the sums of smaller and smaller sin waves can represent pretty much anything in our universe, they might be really confused. But there is no reason they can't.

There is simply no reason that a next-token predicator can't generate a nice-looking checkbox.

antran22 10 hours ago|||
It's still predicting the next word. Somewhere in the gigantic dataset that the LLM was trained on, there is a phrase that says "gradient border" being in the vicinity of a CSS code that render the stuff. Therefore when you run it on an inference loop there's a good chance it output that CSS code when you tell it to render a "gradient border"

Multi-modal models that can understand visual input do exists, but no such visual reasoning process happened in the example you mentioned. Not unless you have a visual feedback loop in the coding harness.

I'm not dismissing the capability of "predicting the next word" however. The vast amount of training data enable extremely complex and useful behavior you just described.

360MustangScope 9 hours ago||
What about things it wasn’t trained on?

For instance I’ve written a few custom languages to learn how to write a VM and the lexer/parser/compiler/etc. that it had never seen before and then just gave it the syntax which is different than what it had ever seen before. Simply due to the fact I made it and it had never been trained on it.

After giving it my documentation, it was able to write the language just like a language that it had been trained on. I’ve also seen this behavior at work where there are weird quirks to do things and definitely not standard and it can handle it.

qsera 8 hours ago|||
Because in its training data there is information on how to map from documentation of a language to actual programs. This means that following the pattern it can map between documentation for any language to programs in that language.

But I think it will have difficulty in crossing paradigm boundaries, by simply using documentation.

skydhash 6 hours ago||||
That’s because it does not encode words or keywords or anything like that. It encodes their relationships. A formal language like a programming language are pretty compact. There’s not much variation between the C-like languages. Just like most Lisps (clojure, scheme, elisp, racket) are fairly similar to each other.

The exact syntax does not matter, only the grammar. If you give it the grammar, and then the keywords, it can find something that has similar grammar and then use your keywords.

YeGoblynQueenne 5 hours ago|||
I'd be very careful assuming something is not in an LLM's training set. Those data sets are truly vast. And, from experience, people tend to miss a lot of their content.

As a for instance, back in the day some academics wrote a paper that compared GPT 3.5 to a couple of inductive programming systems (including one of mine) on solving programming problems in a certain well-known esoteric language which I shall call "L". The task was to solve those programming problems one-shot. The authors asserted that the "L" problem sets were unlikely to be in 3.5's training set, but I found them without much search in a public github repo. I mean the entire dataset was right there. In this case the researchers are colleagues and friends and I know they weren't simply negligent or malicious, they just missed the fact that their "unlikely to be in the training set" data was on the web.

So I'd always assume that if an LLM can perform a task that's because it's seen examples of the task during its training.

Without forgetting that LLMs have this really shockingly powerful ability to interpolate between examples and they can improve their performance on say Task A by training on Task B, where A and B are different but similar.

e.g. they seem to get better at translating between language pairs of which they have few examples of parallel text by training on other pairs of languages for which they have more parallel text; they seem to learn something about language translation in general by training on more examples of translation. I haven't got a good reference on that handy but it's well-known (and of course over-hyped and exaggerated by tech CEOs).

So without wanting to diminish your work, I'd guess that your new language's syntax is different and novel but everything else about it is more ordinary and the similarities are such that an LLM can wing it and write you a lexer etc. After all, the whole point about parser generators and similar tools is that the task can be abstracted and separated from syntax in the first place.

In fact LLMs are very good at that sort of thing, filling in the blanks as it were. I'm old enough to remember the excitement about GPT 3.5 being able to form syntactically correct sentences with nonsensical words give to it.

For example, I just asked Chat [1]:

  Hey chat. The gostak distims the doshes. What happens to the doshes?
And it promptly answered:

  The doshes get distimmed.
See, it even got the spelling right!

_________________

[1] https://chatgpt.com/c/6a242b65-e248-83ed-9a6e-f238a1e871b6

nchie 10 hours ago|||
I understand that to be the "emergent abilities" which are spoken about. There are correlations in the dataset that are strong enough for it to seem to have an understanding which wasn't obvious it would have from simply "predicting the next word".
Marha01 8 hours ago|||
LLMs fundamentally work by predicting the next word (token). But that should not be used to diminish their potential capabilities. It's like saying that human brains "just predict (or produce) the next electrical impulse". Fundamentally correct, but says nothing about the potential emergent capabilities of scaled-up systems that work like that.

Emergent properties of complex systems should not be diminished just because the underlying operating principle is simple.

qsera 8 hours ago|||
>is the LLM is able to represent things in space

It is imitating the text written by humans who can represent things in space.

YeGoblynQueenne 5 hours ago|||
Sorry you're being downvoted for asking a very reasonable question. I don't think any of the replies here address your question either.

If I can do my best to answer, Gemini is a multi-modal system. That means it's trained not only on text but also still images, video and also sound. The training happens in parallel and the representation of each modality is usually different, so the image recognition part is not trained on text tokens but pixels, the video part (probably) on video frames etc. There is some kind of integrated training that goes on so that text can be generated that is correlated to an image and so on, but I don't know the specifics about Gemini in particular. This kind of thing is not exactly new either, you can find systems that captioned images before the rise of LLMs simply by training on examples of images coupled to their textual descriptions.

In that sense it's not entirely correct to call Gemini an "LLM" because it's not only a "language" (or, more precisely, text) model. But LLM I guess becomes a bit of a shorthand for everything based on, or combined with, an LLM.

Anyway that's what's going on: it's not just predicting the next word. It's also predicting the next image frame or the next set of pixels etc associated with the next word.

MagicMoonlight 7 hours ago|||
It can’t. It’s like a Redditor, it just repeats what it has seen other people say.

It has read all of stackoverflow, so it has seen your kind of problem before. Try asking it something really unusual and it will shit the bed.

mjmsmith 4 hours ago||
> It’s like a Redditor, it just repeats what it has seen other people say.

Can stochastic parrots understand irony?

locallost 8 hours ago|||
I don't want to pretend I can explain LLMs, but the same "math" can be applied for visual and non visual things. The dot product of two vectors gives you the angle between them. This is true in 2 or 3 dimensions. But it's also true in 4, 5, 6...n dimensions even though we cannot visualize a 4d space. That it's an angle is relevant for you in the space you can comprehend, but for math or a machine it works in any number of dimensions. So it does need to understand anything visually if the math checks out.
throw310822 10 hours ago|||
LLMs are modelled to predict the next token, and are indeed trained to do so on enormous bodies of text. But to be really good at predicting the next token (word) at the end of a long string of text, you must understand what the text means. If I give you the entire text of a long novel and at the end ask you a single "yes/ no" question about the plot, you only need to emit a single token, but emitting the correct one implies having understood the plot of the novel. This is what LLMs do. They're generating meaningful, coherent text, which implies understanding and cognition at a level that is much deeper than that of the single token they generate at each forward pass. Internally, the LLM has learned to represent the meaning of the entire prompt text, the concepts it implies and its possible continuations far beyond the horizon of simply outputting the next token.
otabdeveloper4 4 hours ago||
> This is what LLMs do. They're generating meaningful, coherent text

No, they generate grammatically coherent text. That is because human language grammars are fundamentally mathematical structures that can be approximated with matrix operations.

They don't generate meaningful text because they have no inherent knowledge of the world.

If you've used LLMs for any amount of time you've already noticed how often they get confused about numeric quantities - like confusing notions of "bigger than" and "less than" or being unable to count letters in words.

This is because any meaning in their output is only accidental.

Ampersander 9 hours ago||
I do agree bigly. Calling what is basically a superhuman brain inside a computer just a "token predictor" is peak thinkslop.
otabdeveloper4 4 hours ago||
Inside the magic AI box is literally nothing but this loop:

    int n_tokens = 0;
    while (n_tokens < TOKENS_MAX) {
        int next_token = decode(context, ++position);
        print(token_to_text(next_token));
        ++n_tokens;
    }
If you don't believe me then just download llama.cpp and see for yourself.
yukIttEft 10 hours ago||
> so the model figures out during training what each token should look for and what it should offer

But how does it learn this token-relationship?

All it has is many text samples, but still, nowhere it says how the tokens relate to each other, so where does this information come from?

HarHarVeryFunny 4 hours ago||
The model is just trying to map from sequence to next token. You could say that it doesn't really care about the relationships between words/tokens - it is just being trained to learn the best attention/etc weights to make this mapping as accurate as possible.

The model could just as well learn to predict next token from gibberish text as long as there were some statistical gibberish regularities to learn. However, if you train it on real meaningful text then the statistical regularities it needs to learn (and will, thanks to gradient descent, and the capable architecture) will be those reflecting "token relationships" - grammar, semantics, etc.

So, you can say the "token relationships" (incl word meanings) are reflected in the statistical regularities of the training data, and the model architecture and training algorithm are just very capable of learning those regularities whatever they may be.

You can consider it related to Word2Vec word embeddings, which are based on the idea that the meaning of words comes from how they are used, which to a first approximation can be implemented by considering the meaning of words to be defined by the words they appear next to(!), which is what the Word2Vec embedding training algorithm does, and famous examples such as "(king - man) + woman = queen" prove that this is in fact learning the meanings of words.

inkysigma 9 hours ago|||
At a high level, the text samples are how the relationships are derived. If we treat text samples as sequences of tokens, then the sequences of tokens describe the joint distributions they occur together which confers the relationship between them. Iirc, this is related to the idea of the distributional hypothesis in NLP: the idea the semantics of words should be similar if they occur in similar situations.
MagicMoonlight 7 hours ago|||
If I handed you thousands of documents which said “Jan-Michael Vincent” all over them, would you need to understand who that is in order to notice the relationship there?
dist-epoch 7 hours ago||
How does evolution learn the form-fitness relationship?

It's the same thing here, you randomly try various token-relationship values and the ones which are slightly better will be favoured.

melvinroest 12 hours ago||
I thought Karpathy’s microgpt explain how LLMs work
disgruntledphd2 11 hours ago|
Microgpt is really good, if you want to understand exactly what happens. I still thought that this article was a good, higher-level complement to that article though.
stalfie 10 hours ago||
This article describes how Transformers work, but not really how LLMs work. Explaining the underlying architecture gives you about as much insight into how a modern LLM behaves as an breakdown of neuronal biochemistry and a few pathways does for the brain. Meaning, almost no insight at all.
rishbz 8 hours ago||
Great insights. RL training is the key
spacebacon 11 hours ago||
But how do they “think”? This is the only repo that can tell you that.

https://github.com/space-bacon/SRT

aabdi 12 hours ago||
this is hard to read...

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

barrenko 11 hours ago|
It's just slop.
mathisdev7 5 hours ago|
very interesting and useful!
More comments...