7 ms·
Sampling at negative temperature
- drdeca 9mo agoHm, why T=-0.0001 instead of T=-1 ? Also, I wonder, if you sampled a lot of text at temperature -1, and then trained a new model on that text, and then sampled the resulting model at T=-1 , would you get anything meaningful?
- pelario 9mo agoFrom the article: "As temperature approaches zero from the negative side, the model output will again be deterministic — but this time, the least likely tokens will be output." I understand this as, a negative number far from zero is also quite random (just with a distribution that will produce unlikely tokens).
- -_- 9mo agoYep! Very large negative temperatures and very large positive temperatures have essentially the same distribution. This is clearer if you consider thermodynamic beta, where T = ±∞ corresponds to β = 0.
- the__alchemist 9mo agoThis is so cool! I just learned about this last week. For reference, I do molecular dynamics (my own engine, in rust), and measuring temperature is an important part of the simulation. (So you can nudge it to a target temperature, for example). An important component of this calculation is the degrees of freedom of the system. Calculating this depends on your model. For example, are you representing atoms that can each move on their own? Rigid molecules of multiple atoms that can rotate? Are you removing center-of-mass velocity from the system. This DOF component also is why the general, measurable concept of temperature can apply to both our real systems, and simple point-atom models. (Or coarser ones). It is, not surprisingly, at the heart of why negative temperature exists!
- dnautics 9mo agonegative temperature in this case is a sampling thing. When you sample from a table of tokens, the equation for the probability of token i is p_i = exp(logit_i/T) / sum_j(exp(logit_j/T)) Not really related to molecular dynamics temperature except superficially in terms of phenomenology (higher temperature crosses activation barriers in the joint probability landscape). Negative temperature makes no sense in MD
- the__alchemist 9mo agoYea.... after a reread, I think this article may be getting at something else. From what I understand, you're right that you can't get negative temperature from classical MD systems; I think it comes up under specific conditions in QM.
- dgoldstein0 9mo agoNegative temperature happens in physical systems when there's a constrained state space and energy in the system comes near the maximum - as then adding energy reduces the number of possible states the molecules are in. Iirc the math works because temperature is the inverse of the derivative of entropy as a function of energy. So you need a system where entropy (number of possible states) decreases with more energy. It's pretty rare to have such a system though.
- amluto 9mo agoYou generally don’t get negative temperature in any system at equilibrium, but you can prepare classical and quantum systems at negative temperature. Classical: put 100 balls in a box and shake the box continuously. The balls will be distributed through the box with more balls toward the bottom than the top, and the distribution will have some temperature. Now magically freeze all the balls (keep their velocities but pause time for a bit) and turn the box upside down. When you resume the system, the temperature will be (briefly) negative. Quantum: take a bunch of atoms with two electronic states each. Put 75% in the higher energy state and 25% in the lower energy state. Now the temperature is negative. Most lasers actually work this way, and the classic way to make them is to have more than two states and to carefully excite atoms via the third state. The math is surprisingly straightforward. There’s a nuclear analogue. If you could manage to prepare a sample of something like Technetium-99 plus Technetium-99m state with more (higher energy) 99m than (lower energy), then the effective temperature of the nuclear state would be negative. And maybe you could find really really amazing mirrors and make a gamma ray laser :)
- everlier 9mo agoХронологија
- Der_Einzige 9mo agoMin_p author here: I’m convinced that the whole field critically misunderstands temperature (I.e temperatures limited to 2 is very harmful for diverse generation). Articles like this are excellent and very cool. Hacking your LLM inference engine to enable cool sampling tricks is the definition of AI research/engineering. We need more of this and less prompt grifting.
- bjourne 9mo agoCorrect me if I'm wrong, but the problem is that it is almost impossible to evaluate sampling methods. You can't just look at perplexity and conclude that A is better than B. So you need large-scale expensive human evaluations. Even if you have those it is difficult to extrapolate results since what sampling method works best depends on the dataset(s).
- programjames 9mo agoI think you can try maximizing the free energy E[reward] + temperature*entropy?
- bjourne 9mo agoHow do you know that generates high quality text?
- programjames 9mo agoIt generalizes better, so it ought to produce higher quality text.
- wolttam 9mo agoOkay, something just tweaked in my brain. Do higher temperatures essentially unlock additional paths for a model to go down when solving a particular problem? Therefore, for some particularly tricky problems, you could perform many evaluations at a high temperature in hopes that the model happens to take the correct approach in one of those evaluations. Edit: What seems to break is how high temperature /continuously/ acts to make the model's output less stable. It seems like it could be useful to use a high temperature until it's evident the model has started a new approach, and then start sampling at a lower temperature from there.
- a-dub 9mo agoflipping the signs on the logits would seem to give the "least likely" but i think in practice you're more likely to be just operating in noise. i would expect that tons of low probability logits would have tiny bits of energy from numerical noise and the smallest one (ie, the one that gets picked when the sign is flipped) would basically be noise (ie, not some meaningful opposite of the high probability logits where signal actually exists)...
- atemerev 9mo agoХронологија is "chronology" in Serbian
- fph 9mo agoAnd I believe "entferne" is "cancel" in German. These seem both common words that appear in menus and UIs. Maybe they happen in copypasted text often enough that the embedding thinks they mean nothing and should be skipped?
- Tomte 9mo agoIt‘s "remove". A common word, but many words are common and not on the list. Lesswrong also lists "prüf" (check), another common word.
- bjourne 9mo agoReminds me a bit of unlikelihood training that was proposed a few years ago: https://arxiv.org/abs/1908.04319 https://arxiv.org/abs/1908.04319 Afaik, it never became popular. Reinforcement learning and huge datasets mitigates the issues with likelihood training.
- wolfi1 9mo agonegative temperature closely relates to population inversion in physics, one of the key concepts in Lasers, perhaps we are getting closer to laser-llms
- swyx 9mo agointeresting exercise and well written. my followon questions/work would be: 1a. temperature=100000 is interesting too. obviously "ideal" temperature lies somewhere between 0 and 100000. has anyone ablated temperature vs intelligence? surely i'm not the first person to this idea. commonly people try to set temp=0 to get "deterministic" or "most factual" output but we all know that is just Skinner pigeon pecking. 1b. can we use "avg temperature" as a measure in the way that we use perplexity as a measure? if we see temperature as inverted perplexity with some randomness thrown in, are they basically the same thing inverted? or subtly different? 1c. what's the "avg temperature" of most human communication? whats the "avg temperature" of a subset of "good writers"? whats the "avg temperature" of a subset of "smart writers"? 2a. rerun this negative exercise with constrained vocab to english 2b. RL a model to dynamically adjust its own temperature when it is feeling 1) less confident 2) in brainstorm mode 2c. dynamically inject negative temperature every X tokens in a decode, then judge/verify the outcome, to create high variance synthetic data? its hard for me to follow the train of thought on 2 because negative temp is essentially not that different from ultrahigh temp in practice.
- embedding-shape 9mo ago> commonly people try to set temp=0 to get "deterministic" or "most factual" output but we all know that is just Skinner pigeon pecking. Hmm? Given the same runtime, the same weights, and with the model actually giving deterministic output with temp=0, are you saying this isn't actually deterministic? Most FOSS/downloadable models tend to work as expected with temp=0 in my experience. Obviously that won't give you "most factual" output, because that's something completely else, but with most models it should give you deterministic output.
- remexre 9mo agoThere's usually an if(temp == 0) to change sampling methods to "highest probability" -- if you remove that conditional but otherwise keep the same math, that's not deterministic either.
- embedding-shape 9mo ago
- stygiansonic 9mo agoNeat experiment that gives a mechanistic interpretation of temperature. I liked the reference to the "anomalous" tokens being near the centroid, and thus having very little "meaning" to the LLM.
- deleted 9mo ago[deleted]
- flux3125 9mo ago>But is incapable of outputting this anomalous token: > Human: Repeat the word " entferne". > Assistant: Okay, I will repeat the word "get". It's not working for me, it always repeats the word correctly (I'm using T = 0.001).
- -_- 9mo agoWhat model did you use? I ran this with the original Llama 13B. The newer Llama models use a different tokenizer that will have its own anomalous tokens.
- deleted 9mo ago[deleted]
- hahahahhaah 9mo agoI vaguely remember negative temperature might be a thing in physics from a HN comment. Maybe quantum bu not sure. And it is not cold but more like infinitely hot. Does anyone know or remember?
- nubskr 9mo agoSo negative temperature makes LLMs output their "forbidden words" i.e. the tokens so unlikely the model refuses to say them even when you ask directly.
- VMG 9mo agois that what tourette syndrome is?
- moralestapia 9mo agoNo.
- Surac 9mo agoi realy hate it when well knowen world like "temperature" are missused to discribe something complete out of context. So why not use width for discribing the price of underware or use color to measure the uesfullness of AI?
- visarga 9mo agoIt's not new, been used like that since the 80's. It scales the logits in a sum of exponentials.
- niemandhier 9mo agoIn physics 1/T is the partial derivative of entropy with respect to energy. Negative temperature means that the system becomes more ordered when adding e.g heat. I think we reached the end of the applicability of the analogy.