Messing around with fine-tuning LLMs, part 2 -- to the cloud!

Posted on 28 April 2024 in Programming, Python, AI

Having fine-tuned a 0.5B model on my own machine, I wanted to try the same kind of tuning, but with an 8B model. My experiments suggested to me that the VRAM required for the tuning was roughly linear with two meta-parameters -- the length of the samples and the batch size -- and I'd found resources online that suggested that it was also linear with the number of parameters.

The 16x scale going from 0.5B parameters to 8B would suggest that I would need 16x24GiB to run this fine-tune, which would be 384GiB. However, the chart I'd seen before suggested I could do it with a bit more than 160GiB -- that being the number they gave for a 7B parameter model.

What I clearly needed to do was find a decent-looking cloud GPU platform where I could start with a smaller machine and easily switch over to a larger one if it wasn't sufficient. Here are my first steps, running one of my existing fine-tune notebooks on a cloud provider.

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Messing around with fine-tuning LLMs

Posted on 27 April 2024 in Programming, Python, AI

Fine-tuning an LLM is how you take a base model and turn it into something that can actually do something useful. Base models are LLMs that have been trained to learn to predict the next word on vast amounts of text, and they're really interesting to play with, but you can't really have a conversation with one. When you ask them to complete some text, they don't know whether you want to complete it as part of a novel, a technical article, or an unhinged tweetstorm. (The obvious joke about which type of people the same applies to is left as an exercise for the reader.)

Chat-like AIs like ChatGPT become possible when a base model has been fine-tuned on lots of texts representing transcriptions (real or fake) of conversations, so that they specialise in looking at texts like this:

Human: Hello!

Bot: Hello, I'm a helpful bot.  What can I do for you today?

Human: What's the capital city of France?


...and can work out that the next word should be something like "The", and then "capital", and so on to complete the sentence: "of France is Paris. Is there anything else I can help you with?"

Getting a solid intuition for how this all works felt like an interesting thing to do, and here are my lab notes on the first steps.

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