Enum MaterializationIntent 

pub enum MaterializationIntent {
    InnerSolve,
    LogdetFactorization,
    OuterEvaluation,
    OuterGradient,
}

What the consumer is going to do with the joint Hessian. This is the intent half of #738’s capability-vs-representation split: the call site states what it needs, and the workspace picks the cheapest representation that serves that need (rather than a single per-workspace preference being applied uniformly regardless of how the result is consumed).

The distinction matters because the same workspace serves several consumers with opposite ideal representations:

• the inner Newton/PCG solve only ever applies H · v, so a matrix-free HVP (Operator) is ideal and a dense build is pure waste;
• the REML logdet term factorizes H + S_λ (Cholesky / eigendecomposition), so it must hold a dense matrix anyway — handing it an Operator only forces an immediate column-basis (or dense_forced) re-materialization, so a workspace with a structural direct-dense build should answer Dense here and skip the operator wrapper entirely.

Workspaces refine their representation choice per intent via [ExactNewtonJointHessianWorkspace::hessian_source_preference_for_intent]; the default keeps the legacy single-preference behaviour so existing workspaces are unchanged.

Variants

InnerSolve

Inner Newton / PCG solve — only applies H · v. Matrix-free is ideal.

LogdetFactorization

REML/LAML logdet term — factorizes H + S_λ, needs a dense matrix.

OuterEvaluation

Outer-Hessian / EFS evaluation — builds the joint hyper terms; today these route through the same source as the gradient path.

OuterGradient

Outer-gradient / IFT term assembly.

Trait Implementations

impl Clone for MaterializationIntent

fn clone(&self) -> MaterializationIntent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for MaterializationIntent

impl Debug for MaterializationIntent

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

Formats the value using the given formatter.

impl Eq for MaterializationIntent

impl PartialEq for MaterializationIntent

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for MaterializationIntent