stan-dev / stan-dev/stan

naturally parameterized multivariate normal

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feature language new function
Dominant language
C++
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Description

From Andrew:

Add a paraemterization of the multivariate normal that takes the parameters Sigma^{-1}*mu and Sigma^{-1} (i.e., the so-called natural parameters of the exponential family) rather than mu and Sigma?

I'm asking because, in this MC-EP thing I'm playing around with, I find myself doing a lot of inverting matrices and solving linear systems in order to get mu and Sigma to pass in to my prior distribution. It's no big deal in terms of "wall time" (the dimensionality is low), I was just wondering.

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Research direction

Locate the multivariate normal distribution implementation and its existing parameterization API. Read how mu and Sigma are represented and tested, then define completion as supporting Sigma^{-1}*mu and Sigma^{-1} directly without requiring the conversions described in the issue, with corresponding tests for the new interface.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
machine-learning
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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