Scalar multiplication with complex numbers and torch.Tensor Scalars

[ausstein]

Issue: Allowing Scalar Multiplications with Complex Numbers in Tensor Trains

Description:

• When using torchTT, scalar multiplications with complex numbers are not supported. This seems to be an oversight as everything works perfectly when they are allowed.
• Also multiplying with torch.Tensor scalars isinstance(other, tn.tensor) raises "TypeError: isinstance() arg 2 must be a type, a tuple of types, or a union"

Steps to Reproduce:

1. Attempt to multiply a tensor train with a complex scalar or torch.Tensor scalar.
2. Observe the error.

Proposed Solution:
I have created a pull request to address this issue by:

• Changing isinstance(other, tn.tensor) to isinstance(other, tn.Tensor) in def __mul__(self, other).
• Adding support for complex scalars by adding or isinstance(other, complex).
• Updating the descriptions and error messages accordingly.

Related Pull Request:

• Link to PR