Struct LocalUpdateSweepPlan 

pub struct LocalUpdateSweepPlan<V> {
    pub steps: Vec<LocalUpdateStep<V>>,
    pub nsite: usize,
}

A complete sweep plan for local updates.

Generated from an Euler tour, this plan specifies the sequence of local update operations for algorithms like truncation and fitting.

Sweep Direction

The sweep follows an Euler tour starting from the root, visiting each edge twice (forward and backward). This ensures all bonds are updated in both directions, which is essential for algorithms like DMRG/TEBD.

nsite Parameter

• nsite=1: Single-site updates. Each step extracts one node.
• nsite=2: Two-site updates. Each step extracts two adjacent nodes (an edge).

Two-site updates are more expensive but can change bond dimensions and are necessary for algorithms like TDVP-2 or two-site DMRG.

Fields

steps: Vec<LocalUpdateStep<V>>

The sequence of update steps.

nsite: usize

Number of sites per update (1 or 2).

Implementations

impl<V> LocalUpdateSweepPlan<V>

where V: Clone + Hash + Eq + Send + Sync + Debug,

pub fn from_treetn<T>( treetn: &TreeTN<T, V>, root: &V, nsite: usize, ) -> Option<Self>

where T: TensorLike,

Generate a sweep plan from a TreeTN’s topology.

Convenience method that extracts the NodeNameNetwork topology from a TreeTN.

pub fn new(network: &NodeNameNetwork<V>, root: &V, nsite: usize) -> Option<Self>

Generate a sweep plan from a NodeNameNetwork.

Uses Euler tour traversal to visit all edges in both directions.

Arguments

• network - The network topology
• root - The starting node for the sweep
• nsite - Number of sites per update (1 or 2)

Returns

A sweep plan, or None if the root doesn’t exist or nsite is invalid.

Example

For nsite=1 on chain A-B-C with root B:

• Euler tour vertices: [B, A, B, C, B]
• Steps: [(B, B), (A, A), (B, B), (C, C)] (each vertex except last)

For nsite=2 on chain A-B-C with root B:

• Euler tour edges: [(B,A), (A,B), (B,C), (C,B)]
• Steps: [({B,A}, A), ({A,B}, B), ({B,C}, C), ({C,B}, B)]

pub fn empty(nsite: usize) -> Self

Create an empty sweep plan.

pub fn is_empty(&self) -> bool

Check if the plan is empty.

pub fn len(&self) -> usize

Number of update steps.

pub fn iter(&self) -> impl Iterator<Item = &LocalUpdateStep<V>>

Iterate over the steps.

Trait Implementations

impl<V: Clone> Clone for LocalUpdateSweepPlan<V>

fn clone(&self) -> LocalUpdateSweepPlan<V>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<V: Debug> Debug for LocalUpdateSweepPlan<V>

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

Formats the value using the given formatter.