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Fine-tuning LLMs is a waste of time

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11–20 of 94 posts

Re: Fine-tuning LLMs is a waste of time

#11
RAG and fine-tuning are suitable for different business scenarios. For some directional and persistent knowledge, such as adjustments for power, energy and other fields, it can bring better performance;

RAG is more oriented to temporary and variable situations.

In addition, LoRA is also a fine-tuning technology,and it is written in their paper.

Re: Fine-tuning LLMs is a waste of time

#12
This is a pretty awful take. Everyone understands they are modifying the weights - that is the point. It’s not like these models were released with all of the weights perfectly accounted for and changing them in any way ruins them. The awesome thing about fine-tuning is that the weights are malleable and you have a great base to start from.

Also the basic premise that knowledge injection is a bad use-case seems flawed? There are countless open models released by Google that completely fly in the face of this. Medgemma is just Gemma 3 4b fine-tuned on a ton of medical datasets, and it’s measurably better than stock Gemma within the medical domain. Maybe it lost some ability to answer trivia about Minecraft in the process, but isn’t that kinda implied by “fine-tuning” something? Your making it purpose built for a specific domain.

Re: Fine-tuning LLMs is a waste of time

#13
Wasn't there that thing about how large LLM's are essentially compression algorithms (https://arxiv.org/pdf/2309.10668)? Maybe that's where this article is coming from, is the idea that finetuning "adds" data to the set of data that compresses well. But that indeed doesn't work unless you mix in the finetuning data with the original training corpus of the base model. I think the article is wrong though in saying it "replaces" the data - it's true that finetuning without keeping in the original training corpus increases loss on the original data, but "large" in LLM really is large and current models are not trained to saturation so there is plenty of room to fit in finetuning if you do it right.

Re: Fine-tuning LLMs is a waste of time

#14

Wasn't there that thing about how large LLM's are essentially compression algorithms ( https://arxiv.org/pdf/2309.10668 )? Maybe that's where this article is coming from, is the idea that finetuning "adds" data to the set of data that compresses well. But that indeed doesn't work unless you mix in the finetuning data with the original training corpus of the base model. I think the article is wrong though in saying it…

Not sure what you mean by “not trained to saturation”. Also I agree with the article, in the literature, the phenomenon to which the article refers is known as “catastrophic forgetting”. Because no one has specific knowledge about which weights contribute to model performance, by updating the weights via fine-tuning, you are modifying the model such that future performance will change in ways that are not understood. Also I may be showing my age a bit here, but I always thought “fine-tuning” was performing additional training on the output network (traditionally a fully-connected net), but leaving the initial portion (the “encoder”) weights unchanged - allowing the model to capture features the way it always has, but updating the way it generates outputs based on the discovered features.

Re: Fine-tuning LLMs is a waste of time

#15
It's pretty frustrating to spend weeks on finetuning and end up with a model that says:

"SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT ..."

Re: Fine-tuning LLMs is a waste of time

#16
post #4

I think of it as trying to encourage the LLM to want to give answers from a particular part of the phase space. You can do it by fine tuning it to be more likely to return values from there, or you can prompt it to get into that part of the phase space. Either works, but fiddling around with prompts doesn't require all that much MLops or compute power. That said, fine tuning small models because you have to power thr…

> That said, fine tuning small models Mostly referred to as model distillation, but I give the author the benefit of the doubt that they didn't mean that.

My understanding of model distillation is quite different in that it trains another (typically smaller) model using the error between the new model’s output and that of the existing - effectively capturing the existing model’s embedded knowledge and encoding it (ideally more densely) into the new.

Re: Fine-tuning LLMs is a waste of time

#17

This is a pretty awful take. Everyone understands they are modifying the weights - that is the point. It’s not like these models were released with all of the weights perfectly accounted for and changing them in any way ruins them. The awesome thing about fine-tuning is that the weights are malleable and you have a great base to start from. Also the basic premise that knowledge injection is a bad use-case seems flawe…

A man who burns his own house down may understand what they are doing and do it intentionally - but without any further information still appears to be wasting his time and doing something stupid. There isn't any contradiction between something being a waste of time and people doing it on purpose - indeed the point of the article is to get some people to change what they are purposefully doing.

He's proposing alternatives he thinks are superior. He might well be right too, although I don't have a horse in the race but LORA seem like a more satisfying approach to get a result than retraining the model and giving LLMs tools seems to be proving more effective too.

Re: Fine-tuning LLMs is a waste of time

#18
post #15

It's pretty frustrating to spend weeks on finetuning and end up with a model that says: "SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT SELECT ..."

What is the way out in such cases?

I've hit this with gemini-2.0-flash and changing the prompt ever so slightly seems to make things work, just to break it at other input.

Re: Fine-tuning LLMs is a waste of time

#19
There is no real difference between fine-tuning with and without a lora. If you give me a model with a lora adapter, I can give you an updated model without the extra lora params that is functionally identical.

Fitting a lora changes potentially useful information the same way that fine-tuning the whole model does. It's just the lora restricts the expressiveness of the weight update so that is compactly encoded.

Re: Fine-tuning LLMs is a waste of time

#20
post #6

"Fine-tuning large language models (LLMs) is frequently sold as a quick, powerful method for injecting new knowledge" Is that true though? I don't think I've seen a vendor selling that as a benefit of fine-tuning.

I think it is a very common misconception (by consumers or businesses trying to use LLMs) that fine tuning can be used to inject new knowledge. I'm not sure many of the fine-tuning platforms do much to disavow people of this notion.
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