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Displacement vector

As explained in Math and Architectures of Deep Learning

A vector describing a change in position or parameters, such as the step taken in parameter space.

A displacement vector describes a change in parameter values. For a one-dimensional parameter w, δw produces a loss change δL; for sufficiently small changes, δL ≈ (dL/dw)δw. Reducing loss therefore requires moving opposite the derivative. section 3.3.1

A two-parameter step

For L(w₀,w₁)=2w₀²+3w₁² at P=(3,4), the loss is 66. The displacement vector [-12,-24]ᵀ points along the negative gradient and gives the greatest local reduction.

How Math and Architectures of Deep Learning covers it

How deep it goes
Derives one-dimensional displacement mathematically and extends the geometry to a two-parameter surface, without implementation details.
Examples
Uses a straight line, a parabola, and a quadratic two-parameter loss surface with a worked displacement vector.
What you can do after
Apply it to choose a loss-reducing direction by opposing the derivative or following the negative gradient.
How it connects
Connects displacement vectors with loss functions, derivatives, gradients, parameter space, and minima.

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Math and Architectures of Deep Learning. The section links point to the parts of the book it draws on.