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That's not quite right. By numerical precision they mean numerical precision, of which quantization is one method to arrive at reduced precision. They also perf
by Vetch 2y ago
That's not quite right. By numerical precision they mean numerical precision, of which quantization is one method to arrive at reduced precision. They also perform experiments where they train from scratch for float32 and float16.
Reasoning, they should have replaced with: iterative computations with accumulating state. This paper, on the impact of quantization, is actually a lot more significant than it appears at first and I think the authors could have done a better job of discussing the broader implications.
The paper's core (and unsurprising) argument is that low-precision arithmetic significantly limits the representational capacity of individual neurons. This forces the model to encode numerical values across multiple neurons to avoid overflow, particularly when storing intermediate computational results. This distributed representation, in turn, increases complexity and makes the model vulnerable to accumulating errors, particularly during iterative operations. It's unclear from my initial reading whether low-precision training (quantization-aware training) is necessary for the model to effectively learn and utilize these distributed representations, or if this capacity is inherent. Regardless, while QAT likely offers benefits, especially with larger numbers, the fundamental limitations of low precision computation persist.
Why not just use a calculator? For some of the same reason humans shouldn't be completely dependent on calculators. It's not just the ability to perform fermi estimates that's constrained but internal computations that require physical "intuition" or modeling the trajectories of physical systems, the ability to work with growing algebraic representations, relative numeric comparisons of large magnitudes (where the model does not internally switch to a favorable format--notice this is easier to do in-context), and representing iterative computation on complex logical chains and hierarchical structures.
Why do we not see this in practice? I contend that we do. There is a small but quite vocal contingent in every LLM forum who insist that quantization, even 8-bits, results in severe degradation in quality despite what most benchmarks say. It's quite likely that common tasks and most tests do not require iterative computations where accumulating state representations must be accurately tracked and these individuals are encountering some of the exceptions.
- prideout 2y agoVery nice analysis, wish I could upvote your comment more than once.