Comment by gpm
6 months ago
The LLM does not "have" a plan.
Arguably there's reason to believe it comes up with a plan when it is computing token propabilities, but it does not store it between tokens. I.e. it doesn't possess or "have" it. It simply comes up with a plan, emits a token, and entirely throws all its intermediate thoughts (including any plan) to start again from scratch on the next token.
I believe saying the LLM has a plan is a useful anthropomorphism for the fact that it does have hidden state that predicts future tokens, and this state conditions the tokens it produces earlier in the stream.
Are the devs behind the models adding their own state somehow? Do they have code that figures out a plan and use the LLM on pieces of it and stitch them together? If they do, then there is a plan, it's just not output from a magical black box. Unless they are using a neural net to figure out what the plan should be first, I guess.
I know nothing about how things work at that level, so these might not even be reasonable questions.
It's true that the last layer's output for a given input token only affects the corresponding output token and is discarded afterwards. But the penultimate layer's output affects the computation of the last layer for all future tokens, so it is not discarded, but stored (in the KV cache). Similarly for the antepenultimate layer affecting the penultimate layer and so on.
So there's plenty of space in intermediate layers to store a plan between tokens without starting from scratch every time.
I don't think that the comment above you made any suggestion that the plan is persisted between token generations. I'm pretty sure you described exactly what they intended.
The concept of "state" conveys two related ideas.
- the sufficient amount of information to do evolution of the system. The state of a pendulum is it's position and velocity (or momentum). If you take a single picture of a pendulum, you do not have a representation that lets you make predictions.
- information that is persisted through time. A stateful protocol is one where you need to know the history of the messages to understand what will happen next. (Or, analytically, it's enough to keep track of the sufficient state.) A procedure with some hidden state isn't a pure function. You can make it a pure function by making the state explicit.
I agree. I'm suggesting that the language they are using is unintentionally misleading, not that they are factually wrong.
This is wrong, intermediate activations are preserved when going forward.
Within a single forward pass, but not from one emitted token to another.
What? No. The intermediate hidden states are preserved from one token to another. A token that is 100k tokens into the future will be able to look into the information of the present token's hidden state through the attention mechanism. This is why the KV cache is so big.
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