Enum ArrowBorderStrategy 

pub enum ArrowBorderStrategy {
    DenseDirect,
    ReducedIterative,
}

Factorization strategy for the arrow-Schur border (shared β) solve, chosen from the shape of the joint system rather than a single fixed border-width cut (ArrowSolverMode::automatic’s DIRECT_SOLVE_MAX_K = 2000).

The border width alone is a blunt selector: it cannot see that the data-fit contribution to the k × k border is only rank Σ_i d_i ≈ n·d. For the #1017 color arm (n = 180, per-row depth d = 2, border k = 15360) the data information is rank 360 yet a dense Direct solve pays a full k³/3 ≈ 1.2e12-flop Cholesky — the measured 26-min-class fit. This maps cleanly onto the two ArrowSolverMode variants the solver already implements.

Variants

DenseDirect

Eliminate the per-row blocks, form the dense k × k reduced Schur, and Cholesky-factor it (ArrowSolverMode::Direct). Appropriate for modest, near-square borders where the k³/3 factorization is cheap and the data-fit rank is comparable to k.

ReducedIterative

Solve the reduced Schur iteratively by matrix-free PCG (ArrowSolverMode::InexactPCG), never materialising the k × k factor. Appropriate when the dense k³ factorization dominates and/or the data-fit contribution to the border is rank-deficient (n·d < k).

Trait Implementations

impl Clone for ArrowBorderStrategy

fn clone(&self) -> ArrowBorderStrategy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ArrowBorderStrategy

impl Debug for ArrowBorderStrategy

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ArrowBorderStrategy

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for ArrowBorderStrategy

impl PartialEq for ArrowBorderStrategy

fn eq(&self, other: &ArrowBorderStrategy) -> 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 Serialize for ArrowBorderStrategy

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ArrowBorderStrategy