Struct ContractionTree 

pub struct ContractionTree { /* private fields */ }

Contraction tree determining pairwise contraction order for N-ary einsum.

When contracting more than two tensors, the order in which pairwise contractions are performed significantly affects performance. ContractionTree encodes this order as a binary tree.

Optimization

Use ContractionTree::optimize for automatic cost-based optimization (e.g., greedy algorithm based on tensor sizes), or ContractionTree::from_pairs for manual specification.

Implementations

impl ContractionTree

pub fn optimize(subscripts: &Subscripts, shapes: &[&[usize]]) -> Result<Self>

Automatically compute an optimized contraction order.

Uses a cost-based heuristic (e.g., greedy algorithm) to determine the pairwise contraction sequence that minimizes total operation count.

Arguments

• subscripts — Einsum subscripts for all tensors
• shapes — Shape of each input tensor

Errors

Returns an error if subscripts and shapes are inconsistent.

pub fn from_pairs( subscripts: &Subscripts, shapes: &[&[usize]], pairs: &[(usize, usize)], ) -> Result<Self>

Manually build a contraction tree from a pairwise contraction sequence.

Each pair (i, j) specifies which two tensors (or intermediate results) to contract next. Intermediate results are assigned indices starting from the number of input tensors.

Arguments

• subscripts — Einsum subscripts for all tensors
• shapes — Shape of each input tensor
• pairs — Ordered list of pairwise contractions

Examples

// Three tensors: A[ij] B[jk] C[kl] -> D[il]
// Contract B and C first, then A with the result:
let subs = Subscripts::new(&[&[0, 1], &[1, 2], &[2, 3]], &[0, 3]);
let shapes = [&[3, 4][..], &[4, 5], &[5, 6]];
let tree = ContractionTree::from_pairs(
    &subs,
    &shapes,
    &[(1, 2), (0, 3)],  // B*C -> T(index=3), then A*T -> D
).unwrap();

Errors

Returns an error if the pairs do not form a valid contraction sequence.