Perturb a LinearOperator with a rank K update.

Inherits From: LinearOperator

This operator acts like a [batch] matrix A with shape [B1,...,Bb, M, N] for some b >= 0. The first b indices index a batch member. For every batch index (i1,...,ib), A[i1,...,ib, : :] is an M x N matrix.

LinearOperatorLowRankUpdate represents A = L + U D V^H, where

L, is a LinearOperator representing [batch] M x N matrices
U, is a [batch] M x K matrix.  Typically K << M.
D, is a [batch] K x K matrix.
V, is a [batch] N x K matrix.  Typically K << N.
V^H is the Hermitian transpose (adjoint) of V.

If M = N, determinants and solves are done using the matrix determinant lemma and Woodbury identities, and thus require L and D to be non-singular.

Solves and determinants will be attempted unless the "is_non_singular" property of L and D is False.

In the event that L and D are positive-definite, and U = V, solves and determinants can be done using a Cholesky factorization.

# Create a 3 x 3 diagonal linear operator.
diag_operator = LinearOperatorDiag(
    diag_update=[1., 2., 3.], is_non_singular=True, is_self_adjoint=True,

# Perturb with a rank 2 perturbation
operator = LinearOperatorLowRankUpdate(
    u=[[1., 2.], [-1., 3.], [0., 0.]],
    diag_update=[11., 12.],
    v=[[1., 2.], [-1., 3.], [10., 10.]])

==> [3, 3]

==> scalar Tensor

x = ... Shape [3, 4] Tensor
==> Shape [3, 4] Tensor

Shape compatibility

This operator acts on [batch] matrix with compatible shape. x is a batch matrix with compatible shape for matmul and