Enum CoefficientCoordinate 

pub enum CoefficientCoordinate {
    Spanning,
    Structural,
}

What a parameter block’s COEFFICIENT COORDINATE is, as opposed to what its column space is (#2748).

The distinction, and why one bit is needed to state it

For most blocks the coefficients are an arbitrary basis: any V with X V spanning range(X) gives the same model, so the identifiability canonicaliser is free to reparameterise β ↦ Vᵀβ, pull the penalties back as VᵀSV, and let crate::Gauge lift the answer home. That freedom is what lets it remove a cross-block structural confound EXACTLY instead of ridging it away.

Some blocks are not like that. The monotone link-wiggle warp is the canonical case: its family imposes β_w ≥ 0 componentwise on those very coefficients, because an I-spline with non-negative coefficients is what makes the learned link monotone. β ↦ Vᵀβ maps that cone to {A V β̃ ≥ 0}, and the hook that produces it (CustomFamily::block_linear_constraints) is a function of the block’s WIDTH — it cannot express A V, so after a reparameterisation it would return a cone in rotated coordinates that means nothing, and the coordinatewise projection beside it (post_update_block_beta) would enforce that nothing. The model would silently stop being monotone.

So “may this block be reparameterised?” is a property of the block’s coordinate, and it is NOT the question ParameterBlockSpec::gauge_priority answers. A priority answers “if a shared direction must be given up, whose is it?” — an ordering AMONG blocks. Reading an ordering as a licence to rotate is how gam#2748 broke: giving the warp a strictly lower priority (correctly, so a cross-block alias stops being unfittable) also lifted the canonicaliser’s equal-priority guard and authorised rotating the one block that cannot be rotated.

Fail-closed

Spanning is the default because it is the common case, but every DERIVATION of this value must resolve doubt toward Structural: declining a reparameterisation always preserves the model (the canonicaliser falls through to the audit gate, which is where it lived before the orthogonalisation pass existed), while performing one on a structural coordinate silently changes it.

Variants

Spanning

Only the block’s column SPACE is model content. Any basis of it is the same model, so a reparameterisation β ↦ Vᵀβ with the penalties and the warm start pulled back is exact.

Structural

The coordinate ITSELF is model content — a componentwise sign cone, a monotonicity ordering, a box the family projects onto, or a geometry the family rebuilds at this exact width. No change of basis preserves the model, and no change of width preserves the family’s own rebuild.

Implementations

impl CoefficientCoordinate

pub fn is_structural(self) -> bool

Does this coordinate carry model structure a reparameterisation would destroy?

Trait Implementations

impl Clone for CoefficientCoordinate

fn clone(&self) -> CoefficientCoordinate

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for CoefficientCoordinate

impl Debug for CoefficientCoordinate

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CoefficientCoordinate

fn default() -> CoefficientCoordinate

Returns the “default value” for a type.

impl Eq for CoefficientCoordinate

impl PartialEq for CoefficientCoordinate

fn eq(&self, other: &CoefficientCoordinate) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for CoefficientCoordinate