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jco4mo30

I would guess that the policy network still outperforms.

 

I agree with this. If you look at Figure 5 in the paper, 5d specifically, you can get an idea of what the policy network is doing. The policy network's prior on what ends up being the best move is 35% (~1/3), which is a lot higher than the 1/361 a uniform prior would give it. If you assume this is average, this policy network would give ~120x linear speed-up in search. And this is assuming no exploration (i.e. the value network is perfect). Including exploration, I think the policy network would give exponential increases in speed.

Edit: Looking through the paper a bit more, they actually use a "tree policy", not a uniform prior, to calculate priors when "not using" the policy network, so what I said above isn't entirely correct. Using 40x the compute with this tree policy would probably (?) outperform the SL policy network, but I think the extra compute used on 40x the search would massively outweigh the compute saved by using the tree policy instead of the SL policy network. The value network uses a similar architecture to the policy network and a forward pass of both are run on every MCTS expansion, so you would be saving ~half the compute for each expansion to do ~40x the expansions.

jco4mo30

Edit: Actually I'm still confused. If I'm reading the paper correctly, the SL policy network is trained to predict what the RL network would do, not to do the thing which maximizes value of information. I'd be pretty surprised if those ended up being the same thing as each other.

 

The SL policy network isn't trained on any data from the RL policy network, just on predicting the next move in expert games.

The value network is what is trained on data from the RL policy network. It predicts if the RL policy network would win or lose from a certain position.

jco4mo10

Thanks for clarifying! I do agree that that wouldn't work, at least if we wanted what was produced to be in any way useful or meaningful to humans.

jco4mo10

I'm not surprised BPEs are semi-coherent. As I said, dark knowledge, and anyway, BPEs are a compression algorithm (compression=intelligence) which were trained on a large English text corpus, so them not being random linenoise is no more surprising than n-grams or gzip being able to generate English-y text.

 

I had this intuition for n-grams (natively) and gzip (from this paper). Never really considered how much BPE compresses the token space, not sure why.

But Whisper-V2 is processing real data still, so it's a mix of learning from data (the Whisper models haven't extracted all possible knowledge from the first pass through the data) and amortizing compute (the training+runtime compute of the Whisper-V2 is being distilled into cleaner pseudo-data for Whisper-V3 to train faster on). You would not generate freeform gibberish, unanchored in any real audio or text, from Whisper-V3 to train V4 and then V5 and then V6 and then V7, and expect V7 to be wildly better.

This makes sense. This made me think whether there'd be some way to chain learning between modalities for a multimodal model, but it would probably fall into the same pit: beyond the initial data, the change in modality would still be producing and learning from synthetic data, not real data as is the case for Whisper.

This knowledge distillation of inner-monologue can be, and has been, done directly, so detouring through a from-scratch RLAIF-ish approach would seem to offer a lot of complexity and downsides compared to just the obvious direct thing.

I do agree that distilling inner monologue is easier than learning the same thing from scratch. I don't think this RLAIF-from-scratch is the end-all-be-all of what's gonna work; I find it a useful frame of thinking for considering other approaches that could work better for learning language more from scratch.

For example, this discussion with you popped the idea of using GANs into my head, which it turns out has been tried extensively. Not to the same scale as next token prediction though. DeepMind has this paper on using a GAN with LSTMs for the generator and discriminator to learn language "from scratch". This survey paper presents other papers using GANs for text generation. Some highlights from quickly skimming through it: 1, 2, 3, 4.

This paper says (paraphrasing the abstract) that GANs are overkill for NLP since minimizing distinguishability (between generator and real outputs) can be seen as maximizing likelihood for NNs with a softmax output layer. I think that being able to define more complex loss functions with GANs is one benefit. You could use multiple discriminators: one for the pre-training data, one for a helpfulness data set, one for a harmlessness data set, etc.

Kind of as an aside, this paper connects GANs to inverse RL (e.g. learning a reward model from human feedback data), and to energy-based models (where Yann LeCun seems to think the future of self-supervised learning is going).

It is also just that there is a world outside language, while there is much less of an outside for logic, math, or Go.

Good point. Maybe what I'm thinking of will only become possible once language models are more grounded in the real world. Multi-modality is a step in that direction, and robotics. We're probably at least a few years from robots collecting enough of their own data in the real world though.

jco4mo10

Obviously this doesn't work "from scratch", you need enough training for the model to be able to distinguish good outputs from bad outputs and also ever produce good outputs on its own. We're not going to get a ChatGPT-Zero. But I think this post does gesture in the general direction of something real.

 

While I do think the process you outlined in your post is more concrete and would probably work better and be easier than learning "from scratch", I don't think it's completely obvious that something like this wouldn't work from scratch. It was done for humans, albeit through billions of years of genetic evolution and thousands of years of cultural evolution. Something like ChatGPT-Zero would probably require many more orders of magnitude of compute than systems we are training today, and also some algorithmic/architectural improvements, but I don't think it's completely impossible.

I feel like your post is implying something similar, given the last sentence, so maybe I'm misinterpreting what exactly you're saying won't work.

jco4mo10

Thanks for the feedback!

LLMs are shockingly good at gibberish, leading to macaronic attacks and other non-obvious implications, so I would not be surprised if an oversight LLM could. (Humans can probably also do this due to dark knowledge but it would be so painful & expensive as to be impractical, as you note.)

I was thinking of the gibberish level of text generated by uniformly sampling from the tokenizer. I had imagined there would be a huge difference between the gibberish level of macaronic attacks and completely random sampling from the tokenizer, but here are the first three examples I generated of 10 tokens uniformly sampled from GPT-2's tokenizer:

  1. "ournament annually amused charismaling Superintendent sushi WiiRONMeat"
  2. " doub arrestAPIogenous ts considersterm Hitler slip autom"
  3. "AAF disposal catches smells interrogation Pilot muscular feminine ITV spree"

These are a lot more intelligible than I would have imagined. I can even reasonably rank these: 3 > 1 > 2.

I also asked ChatGPT-3.5 to rank these, and it ranked them: 3 > 2 > 1.

I used the prompt "Can you rank these three outputs by the coherence of the English language?". The first time I asked, GPT refused to answer because all three are incoherent. I then told it to "Rank them in terms of how close they are to being coherent. They don't have to be completely coherent to be ranked." It then gave me the rankings above.

I repeated this twice more, changing the order of the examples in case it was making decisions based on the numbering. I used the prompt "Can you rank these three outputs by the coherence of the English language? They don't have to be completely coherent to be ranked." For both of these, GPT gave the ranking: 3 > 1 > 2 (numbers changed to match the ones I used in this post).

The most important question to ask about a bootstrap is: "where does improvement come from?" Are you applying compute to extract knowledge that the model already knows implicitly, in a Kolmogorov-complexity-esque sense of 'knows', or are you acquiring more data? And if so, who, where, and what?

Following from what @faul_sname mentioned in their post about improvement being possible "as long as recognizing a good output is easier than generating a good output", I think that improvement is possible from amortizing compute in the form of search. If the teacher model can differentiate between coherent and incoherent paths down the search tree of language, I think a reward model could be trained to predict the coherence of student model outputs and this reward model could be used as the training signal. I am unsure about where the reward model would be initialized from... the teacher model, random initialization, or something else entirely.

I do agree with your point that this will most likely lead to the student model exploiting the teacher model rather than robustly learning language. The "branching factor" (i.e. vocabulary size) of GPT-2 is 50,000. I imagine that the number of ways the student could explore into an observation (token) history that successfully tricks the teacher model is many times more likely than the student stumbling into a robust understanding of language. There are probably ways to mitigate this, similar to precautions taken so RLHF models don't stray too far from the base model.

As for acquiring more data, I think the teacher model could be used to produce "new" data. This is done for Whisper-V3, which was trained on 80% data produced by Whisper-V2. How the teacher LLM generates what it knows is modulated by the temperature. It is trained with a temperature of 1, so generating data with a different temperature (and maybe a less strict top-p) could be seen as generating data on a (slightly) different distribution. Training on this new data could lead to new generation patterns without learning any new facts or knowledge.

None of this would allow the student model to gain knowledge the teacher model does not have, but I think it could allow the student model to more easily access this knowledge. I view this as the model learning to compress the observation (token) history required to approximate some hidden state. A student model that can "reach" a hidden state in 64 tokens is more powerful than one that requires 256 tokens to "reach" the same hidden state.

Perhaps something like Silver & Veness 2010

Will take a look at this, thank you.

something like generating a large argument tree, with key unknowns highlighted, and then after lengthy computations exploring the implications of key claims and bringing in additional 'facts' as they become relevant, the most influential ✕ unknown premise X is kicked up to an oracle (human) for labeling and training on the resulting argument tree?

This and the process @faul_sname outlined in their comment do seem like more concrete methods for eliciting knowledge from compute. Reasoning and math chains can be proven as correct or incorrect, in the same way that Go games can be won or lost, while language is much more subjective.

So you would see a big bank of GPUs churning away, periodically asking the human raters very baffling, arbitrary-seeming, even absurd questions ('Who would win in a fight, a box of nails or a bowl of jelly?'), but where your answer each time resolves a bunch of mysteries for the LLM and reduces its error rate on benchmarks, and where you can periodically finetune or retrain a much better LLM from scratch on the new improved (and highly proprietary?) dataset of text.

Something like this is what I imagined initially for the student model's search over random token space. If someone highly intelligent (e.g. Von Neumann) could rank every output from the model in terms of coherence, I imagine it would result in a model more competent than current LLMs (at least in whatever domains Von Neumann was competent in). Obviously this is impossible, but even getting enough humans of any intelligence level to provide feedback for this process would also be impossible. This is why I fell back to relying on AI feedback for the process. This paper shows that RLAIF performs on par or better than RLHF, although I imagine RLAIF is less robust and more vulnerable to exploitation, as you mentioned. And this result is highly dependent on the domain and which human is giving the feedback.