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Equation 6 · Part 1 · How Mechanistic Interpretability Research Is Actually Done

Symbol a

aa
aa

What this part means

the writing.

Its job in the formula

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

Where the article explains it

Writing a for the activation, z for its sparse code and a^\hat a for the reconstruction,

The passage around this formula

Sparse dictionary learning is the field’s answer, and it is a second and different act of extraction rather than a departure from the first: a sparse autoencoder is trained on the very same activation vectors the probe was reading, learning an overcomplete basis in which each vector is reconstructed as a sparse combination of dictionary elements. Writing a for the activation, z for its sparse code and a^\hat a for the reconstruction,

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Learn the underlying idea

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 article section

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