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Equation 2 · Part 1 · Adapters, Native Pretraining, and Unified Tokens: The Main Multimodal Architectures, Compared

Symbol theta_bridge

θbridge\theta_{\text{bridge}}
θbridge\theta_{\text{bridge}}

What this part means

thetaba_bridge is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

thetaba_bridge is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

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

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Sources cited in the article section

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