stan-dev / stan-dev/stan

base_nuts.hpp:110 — Unnecessary .transpose() on column vector

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Description

Eigen::VectorXd rho = this->z_.p.transpose();
z_.p is a VectorXd (D×1). .transpose() produces a RowVectorXd (1×D), which is
then assigned to a VectorXd (D×1). This works due to Eigen's dynamic resizing
but could trigger debug assertions in strict Eigen builds. Should just be rho
= this->z_.p;.

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Research direction

Review base_nuts.hpp around line 110, focusing on the assignment from z_.p to rho. Confirm that rho uses the VectorXd directly without transpose and that the change compiles successfully under strict Eigen assertions.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
backend
Issue type
Refactor
Difficulty
1/5
Estimated time
Under an hour
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
86/100

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