Struct InverseTensorTrain 

pub struct InverseTensorTrain<T: TTScalar> { /* private fields */ }

Inverse Tensor Train representation

Similar to VidalTensorTrain but stores inverse singular values instead. This is useful for algorithms that need to efficiently apply inverse operations during local updates.

Examples

use tensor4all_simplett::{TensorTrain, AbstractTensorTrain, InverseTensorTrain};

// Build a simple tensor train and convert to inverse form.
let tt = TensorTrain::<f64>::constant(&[2, 3], 1.0);
let inv = InverseTensorTrain::from_tensor_train(&tt).unwrap();

assert_eq!(inv.len(), 2);

// Converting back preserves tensor train values.
let tt2 = inv.to_tensor_train();
let val = tt2.evaluate(&[0, 1]).unwrap();
assert!((val - 1.0).abs() < 1e-12);

// The sum is also preserved: 1.0 * 2 * 3 = 6.0
assert!((tt2.sum() - 6.0).abs() < 1e-10);

Implementations

impl<T: TTScalar + Scalar + Default> InverseTensorTrain<T>

pub fn from_vidal(vidal: &VidalTensorTrain<T>) -> Result<Self>

Create an InverseTensorTrain from a VidalTensorTrain

pub fn from_tensor_train(tt: &TensorTrain<T>) -> Result<Self>

where T: ComplexFloat + BackendLinalgScalar + Copy + 'static, <T as TensorScalar>::Real: TensorScalar + ToPrimitive,

Create an InverseTensorTrain from a regular TensorTrain

pub fn inverse_singular_values(&self, i: usize) -> &DiagMatrix

Get the inverse singular values between sites i and i+1

pub fn all_inverse_singular_values(&self) -> &[DiagMatrix]

Get all inverse singular value matrices

pub fn partition(&self) -> &Range<usize>

Get the partition range

pub fn site_tensors_mut(&mut self) -> &mut [Tensor3<T>]

Get mutable access to site tensors

pub fn set_two_site_tensors( &mut self, i: usize, tensor1: Tensor3<T>, inv_sv: DiagMatrix, tensor2: Tensor3<T>, ) -> Result<()>

Set two adjacent site tensors along with their inverse singular values

pub fn to_tensor_train(&self) -> TensorTrain<T>

Convert to a regular TensorTrain

Trait Implementations

impl<T: TTScalar + Scalar + Default> AbstractTensorTrain<T> for InverseTensorTrain<T>

fn len(&self) -> usize

Number of sites (core tensors) in the tensor train.

fn site_tensor(&self, i: usize) -> &Tensor3<T>

Borrow the rank-3 core tensor at site i.

fn site_tensors(&self) -> &[Tensor3<T>]

Borrow all core tensors as a slice.

fn is_empty(&self) -> bool

Returns true if the tensor train has zero sites.

fn link_dims(&self) -> Vec<usize>

Bond dimensions at every link (length = len() - 1).

fn link_dim(&self, i: usize) -> usize

Bond dimension at the link between site i and site i+1.

fn site_dims(&self) -> Vec<usize>

Physical (site) dimensions for every site.

fn site_dim(&self, i: usize) -> usize

Physical (site) dimension at site i.

fn rank(&self) -> usize

Maximum bond dimension across all links.

fn evaluate(&self, indices: &[LocalIndex]) -> Result<T>

Evaluate the tensor train at a given index set

fn sum(&self) -> T

Sum over all indices of the tensor train

fn norm2(&self) -> f64

Squared Frobenius norm: sum_i |T[i]|^2.

fn norm(&self) -> f64

Frobenius norm: sqrt(sum_i |T[i]|^2).

fn log_norm(&self) -> f64

Logarithm of the Frobenius norm: ln(norm()).

impl<T: Clone + TTScalar> Clone for InverseTensorTrain<T>

fn clone(&self) -> InverseTensorTrain<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug + TTScalar> Debug for InverseTensorTrain<T>

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

Formats the value using the given formatter.