Enum RotationKind 

pub enum RotationKind {
    Real1D,
    Complex2D,
    Quaternion4D,
    Rotor4D,
}

Which rotational-state algebra the block uses for the data-dependent transition rotation absorbed into B/C.

• Real1D — the trivial group: no rotation at all. The transition is the plain scalar decay, i.e. a real SSM (Mamba-2’s transition under Mamba-3’s trapezoid). The in-projection spends no channels on rotation and the cache carries no accumulator (RotationState::Real) — this is the rotation ablation, which is why rope_fraction has no 0.0 setting.
• Complex2D — the abelian SO(2)/complex RoPE that Mamba-3 ships: cumulative angles via cumsum, applied by apply_rope. The default; behaviourally unchanged.
• Quaternion4D — the non-abelian SU(2) ⊂ SO(4) quaternion rotation of this module: cumulative product via quat_cumprod, applied by rotate_state_rank_blocks. Richer state-tracking; selects the RotationState::Quaternion cache accumulator.
• Rotor4D — the whole rotation group of a 4-block, SO(4) ≅ (SU(2)×SU(2))/±1: a two-sided quaternion product v ↦ q ⊗ v ⊗ p̄. Two per-step quaternions instead of one (twice the generator channels, one scan over a doubled block axis); selects the RotationState::Rotor accumulator.

The kinds are a ladder — Real1D ⊂ Complex2D ⊂ Rotor4D and Real1D ⊂ Quaternion4D ⊂ Rotor4D — but the middle two are incomparable, which is why Rotor4D exists. Left multiplication is isoclinic: L_q turns both invariant planes of the block by the same angle (L_i sends 1↦i and j↦k), so Quaternion4D cannot express two independent per-pair angles — it does not contain the abelian rotation it generalises. The right factor opens the full maximal torus (plane angles a−b and a+b for half-angles a, b), and with it every element of SO(4).

Variants

Real1D

No rotation: a real transition (the trivial group). No rotation channels, no cumulative accumulator, B/C pass through untouched.

Complex2D

Abelian complex (SO(2)) RoPE — the current default behaviour.

Quaternion4D

Non-abelian quaternion (SU(2), left-isoclinic) rotation.

Rotor4D

The full SO(4) rotation of each 4-block: two-sided v ↦ q ⊗ v ⊗ p̄.

Implementations

impl RotationKind

pub fn quat_factors(self) -> usize

How many cumulative-rotation quaternions the accumulator carries per (head, 4-block): one for Quaternion4D, two for Rotor4D (the left and right factors). Meaningless for the non-quaternion kinds (Complex2D accumulates angles, Real1D accumulates nothing) — reported as 1.

The factors are stacked along one block axis, so every quaternion primitive — the generator split, quat_from_scaled_axis, the quat_cumprod scan, quat_normalize — runs once over quat_factors · blocks blocks and needs no Rotor4D branch of its own. Only the application to B/C differs.

Trait Implementations

impl Clone for RotationKind

fn clone(&self) -> RotationKind

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for RotationKind

impl Debug for RotationKind

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

Formats the value using the given formatter.

impl Default for RotationKind

fn default() -> RotationKind

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for RotationKind

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for RotationKind

impl PartialEq for RotationKind

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for RotationKind

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 RotationKind