FR: `model_base` methods - use `Eigen::Ref<Eigen::VectorXd>`
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Description
Summary:
The Eigen overloads for model base methods like log_prob and unconstrain_array only accept Eigen::VectorXd inputs, which can require some data-reshaping/copying for downstream interfaces.
If these could be changed to Eigen::Ref<Eigen::VectorXd> (or overloads for these added), then the current Stan behaviour would be unchanged but interfaces could then pass Eigen::Map<Eigen::VectorXd> types and avoid extra copies
Current Version:
v2.35.0
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the model base Eigen overloads for methods such as log_prob and unconstrain_array, then inspect how their current Eigen::VectorXd parameters are used. Done means preserving current Stan behavior while accepting Eigen::Ref<Eigen::VectorXd> or suitable overloads so downstream interfaces can pass Eigen::Map<Eigen::VectorXd> without extra copies.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- backend-api-design
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100