Comment by bob1029
4 days ago
I think certain classes of artificial neural networks are definitely more interpretable than others.
For example, a trillion-parameter transformer model built using many layers is likely significantly easier to read than one that only has a few million parameters but was constructed using neuroevolution over one gigantic layer.
The degree to which a model can be quantized without losing its performance also likely contributes to interpretability. The redundancy can help humans lock onto patterns. If there is no redundancy at all (everything is a surprise in information theoretical terms), then the stream of parameters will look indistinguishable from cosmic background radiation.
> a trillion-parameter transformer model built using many layers is likely significantly easier to read than one that only has a few million parameters but was constructed using neuroevolution over one gigantic layer.
Why do you believe this?
Neuroevolution is a discontinuous way to go about building the network. You are evolving the topology itself from zero. You don't know how many parameters you will have until the training is complete (if it ever does). With a transformer model you start with a known-good topology and can calculate how long a training run will take.
Yes. In that sense it is equivalent to a compression method that uses K-means clustering to do the partitioning. But because there are many more bits of knowledge out there than there are bits in the models you end up with this amorphous smear. I'm sure some of those bits carry more information about some of the concepts but in general - and that's the way it is explained in just about all the papers I've read that I can still comprehend - every weight contributes to the output in a dense model. In an MOE things get more complicated but there within every 'MOE' column the same principle applies.
I'm fine with taking this article at the high level conceptual level, that's effectively the kind of thinking that led to MOE to begin with. But I don't see that as a pathway to being able to 'explain' a model. Because if you could actually explain a model you could engineer the weights, you wouldn't need any training because it implies that you can improve on the model by simply performing surgery on the weights to get it to do what it does but better. Now, obviously, unlike the author I'm a complete nobody but for the last two years or so I've been trying very hard to understand what is going on under the hood.
It's akin to feature engineering - or rather, the lack thereof - and to see a strong suggestion that we maybe be able to reverse that is interesting, but absent hard proof at how a particular model reached a particular conclusion it is difficult to give that a lot of weight right now. It is possible that such proof is buried somewhere in TFA and I overlooked it during reading. But I think this is speculative rather than that it proves anything and before I'm going to be convinced I would like a little more evidence.
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羊.
This is a Chinese character that can refer to goats, rams, and several other kinds of "medium-sized animal with thick wooly coats and horns". English has no direct equivalent; we have to be too specific when we talk about these animals.
A model with a small number of neurons has to compact its concepts in order to fit within the parameter count while reducing loss. OP's article shows that the compaction is usually generalization: "goat" and "ram" get compressed into "羊". The canonical example of superposition, an image model where "car" feeds into a bunch of "dog" features, was shown to be actually generalization. In a sense, the model was so small that its optimizer didn't have the parameter budget to distinguish between "car" and "dog"; it has a single set of "thing that moves fast" features.
So basically, really small models are merging features into semantic buckets that are so generalized they don't make sense to big human brains unless we really, really squint. The buckets chosen happen to be what has the lowest loss, of course.
Ok, so assuming that this all holds: you could then create a model that is substantially larger than the ones that we have now and at some point the model would become sparse: there would be ample space to accommodate all of the information in the input without weights ever carrying more than one piece of information. The degree to which you get overlap is then a function of the ratio between the size of the model and the size of the input and this is pretty much in line with the conventional way of looking at models (unless I'm grossly mistaken). So by reducing the size of the model relative to the size of the input you force the model to co-locate multiple pieces of information to the point that they start to resemble each other more and more.
But from my earliest experiments with this stuff that's not really what happens. Yes, you get 'feature like' regions in the models. But those feature like regions, even though they encode something particular do not encode concepts the way we would normally use them and I fail to see how this pathway would lead to an explainable model in the sense that would could use something simpler than the model itself to predict its output with a high degree of fidelity.
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Possibly the best and most succinct explanation in the thread thus far.
The posted article argues this many times...
Yes, but it is the same person making the same argument many times. There have been large multitudes of articles by others who are arguing the opposite. It could well be true. But it would take a lot more than just one over-wordy, distraction imaged, clearly co-written by AI article to convince me of that.
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The reason why transformers are the best architecture has to do with the fact that tokenization introduces a variable quantity of manipulable objects with cross interactions.
You can think of each token as a semantic database row with semantic properties (color, shape, etc) associated with said row. Classic NNs have to waste neurons on composite representations like "dark circle" because if they had just color or similar properties they run into the issue that e.g. a classification must classify the color of the entire image rather than the color of an object inside the scene. To get around that limitation, the network has to then implicitly tie concepts like color into the depicted object (dark circle) so that it retains the ability to distinguish the objects from the property the object has.
What a transformer does is basically reuse the same network over and over again on each abstract semantic database row but not just in the classic RNN fashion where you only have the current state. The transformer calculates the token by taking every other token into account. The K matrix forms a classifier network on the fly that detects the relevancy of a token pair and the V matrix forms a regressor network that takes the token pair and produces the expected output of the combination of the two tokens. When you combine the relevancy plus the regressor output you get a weighted sum, essentially emulating an arbitrary function that has read the past input (like a turing machine).
Edit: This also means that you should bet against single state systems like Mamba. The system needs to be able to deal with multiple parallel states and recombine them (e.g. via attention). Single state Mamba is dead! Long live parallel state Mamba!
Edit 2: We should also start questioning the concept of a token altogether since it is equivalent to an inflexible flat database row. What we really need is the concept of a token group where one part of the token refers to the key and the other part of the token refers to the value for that key. This would give each token the ability to encode an arbitrary JSON style document or an arbitrary self contained graph.