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Equation 5 · Part 2 · Adapters, Native Pretraining, and Unified Tokens: The Main Multimodal Architectures, Compared

subscript

θLM\theta_{\text{LM}}
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

This is the formal shape of “freeze the backbones”: the gradient update is masked to zero everywhere except the bridge parameters θbridge\theta_{\text{bridge}} , so |θbridge\theta_{\text{bridge}}| — a few hundred million parameters in BLIP-2’s case, dramatically fewer than either tower — is the entire quantity being optimised, and θvision\theta_{\text{vision}} and θLM\theta_{\text{LM}} contribute a forward pass but never a gradient.

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

Sources cited in the article section

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