Fine-tuning LMs as a way to move compute back from inference to training
Apr 1, 2024
Alexander Junge
2 minute read

As I was reading this review paper on tool use for language models (LMs) over the Easter holidays, a thought crossed my mind:

There is an interesting trend when working with LMs in production to perform more and more computations at inference time. For example, tool-using agents, multiagent systems, elaborate state machines, and ever more complicated RAG systems like CRAG are becoming popular since they tend to give better responses. The goal is often to provide deliberative System-2-like responses, rather than instinctive System-1-like responses (following the System 1 and System 2 distinction coined by the late Daniel Kahneman and Amos Tversky; excuse the anthropomorphism here).

However, this trend leads to increasing response times and inference costs, degrading user experience. Fine-tuning, on the other hand, can be seen as a way to move compute from inference time back to training time. Instead of relying on large, generalist LMs, fine-tuning allows us to reverse this trend and use smaller, faster, and cheaper specialist LMs. Fine-tuning of course requires extra compute during training, but allows to run a smaller model at inference time, reducing inference compute, response times, and inference costs.

Don’t think this is a particularly groundbreaking idea but I think it’s a useful mental model when thinking about fine-tuning.

PS: a related thought is that as more compute is spent at inference time, the fair evaluation of LM-based systems is becoming a more complex topic. I guess besides disclosing performance metrics, inference compute spend and latency should start to be widely disclosed as well.

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