stan-dev / stan-dev/math

truncated PRNGs

Open
#214 14 comments 1 reaction 0 assignees View on GitHub

Nobody has claimed this yet.

feature new function
Dominant language
C++
Stars
839
Forks
220
Avg merge
2d 4h
Merged PRs (30d)
14

Description

It'd be nice to be able to match our models and do something like this:

sigma_sim <- normal_rng(mu, sigma) T[lb, ];

to get a truncated form of the normal (and so on for upper and lower bounds and just upper bounds).

What we need in this repo is truncated forms of the PRNGs. Rejection sampling won't be robust enough and writing a slice sampler seems like a huge pain and I'm not even clear it'll work for fat tails like the Cauchy or constrained distributions without transformed. Will this have to wait until we have inverse CDFs?

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

No files, tests, or entry points are named. Start by locating the existing PRNG implementations and their tests, then determine how truncated normal and other distributions would be represented; done would require a decided, robust approach for the requested bounds and distributions.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
backend
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
20/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.