[WIP] Partial optimal transport 1d solver

[rtavenar]

...from Chapel & Tavenard 2025

Types of changes

It introduces an efficient partial optimal transport solver for 1d problems

Motivation and context / Related issue

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.10%. Comparing base (99477be) to head (98967fb).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #741   +/-   ##
=======================================
  Coverage   97.09%   97.10%           
=======================================
  Files         100      101    +1     
  Lines       20432    20459   +27     
=======================================
+ Hits        19839    19866   +27     
  Misses        593      593           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull Request Overview

This PR adds an efficient 1D partial optimal transport solver implemented in Cython with a Python wrapper, updates packaging to include the new extension, and provides basic tests.

• Introduces partial_wasserstein_1d in ot.partial, backed by a Cython routine.
• Registers a new Cython extension partial_cython in setup.py.
• Adds tests for dimensionality checks and correctness of 1D solver outputs.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/test_partial.py	New tests for error on non-1D input and basic functional tests
setup.py	Added partial_cython extension to cythonize call
ot/partial/partial_solvers.py	Imported and exposed the Python wrapper partial_wasserstein_1d
ot/partial/partial_cython.pyx	Complete Cython implementation of the 1D partial Wasserstein solver
ot/partial/init.py	Exported partial_wasserstein_1d in the package API

Comments suppressed due to low confidence (2)

ot/partial/partial_solvers.py:1308

• The docstring states it "returns the OT matrix", but the function actually returns (indices_x, indices_y, marginal_costs). Please update the brief description to reflect the actual return values.

    r"""Solves the partial Wasserstein distance problem between 1d measures and returns

test/test_partial.py:62

• [nitpick] The test comments mention non-1D inputs but don’t define xs and xt with invalid shapes. Consider explicitly creating e.g. xs = np.zeros((5,2)), xt = np.zeros((5,2)) before calling to ensure the assertion is triggered.

    with pytest.raises(AssertionError):

[rtavenar]

OK I have something I am rather happy with. My last step would be to move from list/dict/set implementation to only numpy arrays and benchmark efficiency.

@rflamary maybe you can have a look at the PR before this last step, as that should not impact too much the overall integration of the method in the package (docs, example and API should stay the same).

Also, I'm not sure when I will have time for this last step (should either be tomorrow or in 1-2months).