RFC: oneDAL 2026.0: DAAL API layers of certain algorithms deprecations

[Vika-F]

Description

Work is in progress

This RFC proposes to deprecate API layers of the select algorithms available in the DAAL as part of the ongoing transition to the modern oneDAL API.

In contrast to PR #3400, this RFC proposes removing only the API layers while preserving all underlying
algorithmic computational kernels.

A rendered variant of this RFC: https://github.com/Vika-F/daal/blob/dev/interfaces_removal/rfcs/20251022-daal-interfaces-deprecation/README.md

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Checklist:

Completeness and readability

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes or created a separate PR with updates and provided its number in the description, if necessary.
• Git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details).
• I have resolved any merge conflicts that might occur with the base branch.

Testing

• I have run it locally and tested the changes extensively.
• All CI jobs are green or I have provided justification why they aren't.
• I have extended testing suite if new functionality was introduced in this PR.

Performance

• I have measured performance for affected algorithms using scikit-learn_bench and provided at least a summary table with measured data, if performance change is expected.
• I have provided justification why performance and/or quality metrics have changed or why changes are not expected.
• I have extended the benchmarking suite and provided a corresponding scikit-learn_bench PR if new measurable functionality was introduced in this PR.

[david-cortes-intel]

@Vika-F Would the entries in this list cover the dsitributed mode interfaces?

[david-cortes-intel]

@Vika-F What about others like low order moments? As in here: #3401

[Vika-F]

@david-cortes-intel If we are Ok to remove daal4py APIs for distributed algorithms, I can list the distributed APIs here as well.
For now I am listing only the algorithms that already have oneDAL APIs.

[Vika-F]

@david-cortes-intel yes, I plan to add low order moments and maybe something else, like kernel functions - but I need to check first that their DAAL APIs are not used elsewhere.

[david-cortes-intel]

@david-cortes-intel yes, I plan to add low order moments and maybe something else, like kernel functions - but I need to check first that their DAAL APIs are not used elsewhere.

How would it work if we remove the batch containers without removing the distributed ones? Wouldn't daal4py stop working either way if it parses the general headers which are not specific to distributed implementations?

[Alexandr-Solovev]

@Vika-F Does it make sense to mention all of the algorithms here? Bc I hope we can apply the same deprecations for each algo