Add Scaled Sigmoid Link and Generic Inverse

[simon-hirsch]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces two new scaled sigmoid link functions and a generic inverse link to facilitate function inversion.

• Added ScaledInverseSigmoidLink and ScaledSigmoidLink in sigmoidlinks.py with methods for the link, its inverse, and corresponding derivatives.
• Introduced a GenericInverseLink in generic.py to swap the link functions and derivatives.
• Updated init.py files to expose the new link functions and the GenericInverseLink.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/rolch/link/sigmoidlinks.py	Added implementations for two scaled sigmoid links with their respective methods.
src/rolch/link/generic.py	Added a GenericInverseLink class to invert provided link functions.
src/rolch/link/init.py	Updated module exports to include the new sigmoid links and generic inverse link.
src/rolch/init.py	Updated package exports to include the new link functions.

Comments suppressed due to low confidence (2)

src/rolch/link/sigmoidlinks.py:38

• In ScaledInverseSigmoidLink.inverse_derivative, the multiplication by (self.upper - self.lower) and subsequent division by (self.upper - self.lower) cancel each other out. Simplify the expression to 'sigmoid(x) * (1 - sigmoid(x))' for clarity.

* (1 - sigmoid(x)) / (self.upper - self.lower)

src/rolch/link/sigmoidlinks.py:80

• In ScaledSigmoidLink.link_derivative, the factor (self.upper - self.lower) is multiplied then divided by the same term, resulting in redundancy. Consider simplifying the derivative to eliminate the unnecessary operations.

* (1 - sigmoid(x)) / (self.upper - self.lower)

[BerriJ]

This is misleading, we want to pass the support of the inverted link function here, right?

Suggested change

	link_support (Tuple): The support of the link function
	link_support (Tuple): The support of the inverted link function

[BerriJ]

This is a great Idea! However, before merging this I'd like to make the following changes:

• Rename generic.py to generic_inverse.py as the "generic" link function is defined in rolch/base/link. This way we make it more explicit that this only contains a generic inverse link.
• Adjust implementation of InverseSoftPlusLink this is a natural candidate to inherit from the new class, so we need an implementation of the non inverted SoftPlusLink
• Update docs
• Think about special cases such as links with subclasses: SqrtLink > SqrtShiftTwoLink > SqrtShiftValueLink

For now, we should move this into the draft stage IMHO.