Function contract_multi 

pub fn contract_multi(
    tensors: &[&TensorDynLen],
    allowed: AllowedPairs<'_>,
) -> Result<TensorDynLen>

Contract multiple tensors into a single tensor, handling disconnected components.

This function automatically handles disconnected tensor graphs by:

1. Finding connected components based on contractable indices
2. Contracting each connected component separately
3. Combining results using outer product

Arguments

• tensors - Slice of tensors to contract
• allowed - Specifies which tensor pairs can have their indices contracted

Returns

The result of contracting all tensors over allowed contractable indices. If tensors form disconnected components, they are combined via outer product.

Behavior by N

• N=0: Error
• N=1: Clone of input
• N>=2: Contract connected components, combine with outer product

Errors

• AllowedPairs::Specified contains a pair with no contractable indices

Examples

use tensor4all_core::{TensorDynLen, DynIndex, contract_multi, AllowedPairs};

// A[i, j] and B[j, k] share index j — contract to get C[i, k]
let i = DynIndex::new_dyn(2);
let j = DynIndex::new_dyn(3);
let k = DynIndex::new_dyn(4);

let a = TensorDynLen::from_dense(
    vec![i.clone(), j.clone()],
    vec![1.0_f64; 6],
).unwrap();
let b = TensorDynLen::from_dense(
    vec![j.clone(), k.clone()],
    vec![1.0_f64; 12],
).unwrap();

let c = contract_multi(&[&a, &b], AllowedPairs::All).unwrap();
assert_eq!(c.dims(), vec![2, 4]);