Numpy's einsum
only works with dense tensors.
Is there an alternative that also works with sparse tensors and linear operators?
For example, I might have a function f
that computes matrix vector multiplications of the form $A^{-1}x$ for some matrix $A$. Numpy's
einsum
doesn't even allow
np.einsum('ij,j',A,x)
let alone
np.einsum('ijkl,mj->imkl',X,A)
The same operations also don't work when $A$ is a sparse matrix (let alone a general sparse tensor).
While the LinearOperator support is more of a convenience question, the support for sparse tensors is crucial to me.