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Unnormalized distribution

An unnormalized distribution is a nonnegative function assigning relative weights to outcomes whose total mass or integral has not been scaled to one.

How 2 Manning books explain it

Fabulous Adventures in Data Structures and Algorithms

A non-normalized probability density function is a nonnegative function proportional to a continuous distribution's density but not necessarily integrating to one.

How it is used
Enables sampling from continuous posterior densities when their evidence-dependent normalizing constant is unavailable.
How deep it goes
Works through constant cancellation, consistent likelihood scaling, and Metropolis weight ratios; leaves initial and proposal selection for further consideration.
Examples
Uses a C# posteriorPDF expression, a continuous uniform weight function, and a Metropolis transition that compares target weights.
What you can do after
Build it from scratch as a continuous posterior weight function and apply it via Metropolis without computing the evidence probability.

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Machine Learning Algorithms in Depth

An unnormalized distribution assigns probability weights proportional to a distribution density but lacks the factor required for its total mass to equal one.

How it is used
Supports importance sampling when target or proposal normalization constants are unknown.
How deep it goes
Derives unnormalized weights and partition-function ratios, then analyzes estimator variance and consistency.
Examples
Uses a power-exponential target, a scaled truncated Gaussian proposal, and a from-scratch importance-sampling implementation.
What you can do after
Apply it via importance sampling to estimate expectations without explicitly evaluating normalization constants.

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Related concepts

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