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Equation 2 · Part 8 · Actually Deploying an Open-Weight Model in Production

Symbol r

W=W0+ΔW=W0+BA,B∈Rd×r, A∈Rr×k, r≪min⁡(d,k)W = W_0 + \Delta W = W_0 + BA, \qquad B \in \mathbb{R}^{d \times r},\ A \in \mathbb{R}^{r \times k},\ r \ll \min(d, k)
rr

What this part means

r appears in the objective or constraint used by the optimization on the right.

Its job in the formula

r appears in the objective or constraint used by the optimization on the right.

The passage around this formula

…k} , LoRA represents the adapted weight as W=W0+ΔW=W0+BA,B∈Rd×r, A∈Rr×k, r≪min⁡(d,k)W = W_0 + \Delta W = W_0 + BA, \qquad B \in \mathbb{R}^{d \times r},\ A \in \mathbb{R}^{r \times k},\ r \ll \min(d, k). Only B and A are trained; W0W_0 never moves during fine-tuning [ 5 ] . The effect on trainable parameter count for that one matrix is to fall from dk to r(d + k) , which is small whenever the chosen rank r is small relative to d and k — and because BA can be merged back into W0W_0 after training, LoRA adds no extra inference latency once deployed. Hu and colleagues report, for their comparison against full fine-tuning of GPT-3 175B, up to a…

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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

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