ENH Add Array API compatibility to mean_absolute_error

[EdAbati]

Reference Issues/PRs

Towards #26024

What does this implement/fix? Explain your changes.

It makes the mean_absolute_error implementation compatible and tested with the Array API.

Not sure if it's the best approach, but I have converted the np.average implementation so that it is compatible with the Array API. Is there a better way? (I will fix add the tests to make codecov happy, if you agree to have the _average function)

cc @betatim @ogrisel

[github-actions]

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[ogrisel]

Thanks for the PR. Could you please expand the tests to make sure that we cover the raised exceptions?

More details below.

[ogrisel]

Thanks! One more suggestion for a more informative message. The test needs to be updated accordingly.

BTW, I think that numpy error message would benefit from a similar treatment upstream.

[EdAbati]

BTW, I think that numpy error message would benefit from a similar treatment upstream.

I will make an issue on numpy to see if they are intrested in updating the messages :)

Also BTW I added a set of tests for multioutput='raw_values' to check when the output is an array and not a float: 48bd567

[ogrisel]

I launched the Array API tests with pytorch with an MPS device on my local laptop and with pytorch on a machine with a cuda device and all the mean absolute error Array API compliance tests pass.

However I observed some failures with cupy:

FAILED sklearn/metrics/tests/test_common.py::test_array_api_compliance[mean_absolute_error-check_array_api_regression_metric-cupy.array_api-None-None] - AttributeError: module 'cupy.array_api' has no attribute 'swapaxes'
FAILED sklearn/metrics/tests/test_common.py::test_array_api_compliance[mean_absolute_error-check_array_api_multioutput_regression_metric-cupy-None-None] - TypeError: Implicit conversion to a NumPy array is not allowed. Please use `.get()` to construct a NumPy array explicitly.
FAILED sklearn/metrics/tests/test_common.py::test_array_api_compliance[mean_absolute_error-check_array_api_multioutput_regression_metric-cupy.array_api-None-None] - ValueError: Unsupported device 'cpu'

Here are the details of the tracebacks:

Details

=============================================================== FAILURES ===============================================================
______________ test_array_api_compliance[mean_absolute_error-check_array_api_regression_metric-cupy.array_api-None-None] _______________

metric = <function mean_absolute_error at 0x7ff1b90f0b80>, array_namespace = 'cupy.array_api', device = None, dtype = None
check_func = <function check_array_api_regression_metric at 0x7ff1714e4280>

    @pytest.mark.parametrize(
        "array_namespace, device, dtype", yield_namespace_device_dtype_combinations()
    )
    @pytest.mark.parametrize("metric, check_func", yield_metric_checker_combinations())
    def test_array_api_compliance(metric, array_namespace, device, dtype, check_func):
>       check_func(metric, array_namespace, device, dtype)

sklearn/metrics/tests/test_common.py:1873: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
sklearn/metrics/tests/test_common.py:1810: in check_array_api_regression_metric
    check_array_api_metric(
sklearn/metrics/tests/test_common.py:1747: in check_array_api_metric
    metric_xp = metric(y_true_xp, y_pred_xp, sample_weight=sample_weight)
sklearn/utils/_param_validation.py:214: in wrapper
    return func(*args, **kwargs)
sklearn/metrics/_regression.py:214: in mean_absolute_error
    output_errors = _average(xp.abs(y_pred - y_true), weights=sample_weight, axis=0)
sklearn/utils/_array_api.py:651: in _average
    weights = xp.swapaxes(weights, -1, axis)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <sklearn.utils._array_api._ArrayAPIWrapper object at 0x7ff1b5d40730>, name = 'swapaxes'

    def __getattr__(self, name):
>       return getattr(self._namespace, name)
E       AttributeError: module 'cupy.array_api' has no attribute 'swapaxes'

sklearn/utils/_array_api.py:203: AttributeError
_____________ test_array_api_compliance[mean_absolute_error-check_array_api_multioutput_regression_metric-cupy-None-None] ______________

metric = <function mean_absolute_error at 0x7ff1b90f0b80>, array_namespace = 'cupy', device = None, dtype = None
check_func = <function check_array_api_multioutput_regression_metric at 0x7ff1714e4310>

    @pytest.mark.parametrize(
        "array_namespace, device, dtype", yield_namespace_device_dtype_combinations()
    )
    @pytest.mark.parametrize("metric, check_func", yield_metric_checker_combinations())
    def test_array_api_compliance(metric, array_namespace, device, dtype, check_func):
>       check_func(metric, array_namespace, device, dtype)

sklearn/metrics/tests/test_common.py:1873: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
sklearn/metrics/tests/test_common.py:1831: in check_array_api_multioutput_regression_metric
    check_array_api_metric(
sklearn/metrics/tests/test_common.py:1754: in check_array_api_metric
    assert_allclose(
sklearn/utils/_testing.py:284: in assert_allclose
    actual, desired = np.asanyarray(actual), np.asanyarray(desired)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

>   ???
E   TypeError: Implicit conversion to a NumPy array is not allowed. Please use `.get()` to construct a NumPy array explicitly.

cupy/_core/core.pyx:1475: TypeError
________ test_array_api_compliance[mean_absolute_error-check_array_api_multioutput_regression_metric-cupy.array_api-None-None] _________

metric = <function mean_absolute_error at 0x7ff1b90f0b80>, array_namespace = 'cupy.array_api', device = None, dtype = None
check_func = <function check_array_api_multioutput_regression_metric at 0x7ff1714e4310>

    @pytest.mark.parametrize(
        "array_namespace, device, dtype", yield_namespace_device_dtype_combinations()
    )
    @pytest.mark.parametrize("metric, check_func", yield_metric_checker_combinations())
    def test_array_api_compliance(metric, array_namespace, device, dtype, check_func):
>       check_func(metric, array_namespace, device, dtype)

sklearn/metrics/tests/test_common.py:1873: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
sklearn/metrics/tests/test_common.py:1831: in check_array_api_multioutput_regression_metric
    check_array_api_metric(
sklearn/metrics/tests/test_common.py:1752: in check_array_api_metric
    metric_xp = xp.asarray(metric_xp, device="cpu")
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

obj = Array([0.5, 1. ], dtype=float32)

    def asarray(
        obj: Union[
            Array,
            bool,
            int,
            float,
            NestedSequence[bool | int | float],
            SupportsBufferProtocol,
        ],
        /,
        *,
        dtype: Optional[Dtype] = None,
        device: Optional[Device] = None,
        copy: Optional[bool] = None,
    ) -> Array:
        """
        Array API compatible wrapper for :py:func:`np.asarray <numpy.asarray>`.
    
        See its docstring for more information.
        """
        # _array_object imports in this file are inside the functions to avoid
        # circular imports
        from ._array_object import Array
    
        _check_valid_dtype(dtype)
        if device is not None and not isinstance(device, _Device):
>           raise ValueError(f"Unsupported device {device!r}")
E           ValueError: Unsupported device 'cpu'

/data/parietal/store3/work/ogrisel/mambaforge/envs/dev/lib/python3.10/site-packages/cupy/array_api/_creation_functions.py:59: ValueError
======================================================= short test summary info ========================================================

[ogrisel]

For the swapaxes problem, we should report the problem upstream (if not already existing) and mark it the corresponding test case as xfail in the scikit-learn test suite with a link to the upstream issue. For information, I am running the 12.2.0 version of cupy which is the latest available on conda-forge apparently.

[ogrisel]

The following might fix the other 2 failures with cupy.

You can probably use google colab or kaggle code if you need a machine with a cuda device to launch the tests with cupy.

[EdAbati]

Thank you very much for checking cupy :)

I've added the suggestions, but I still have to test if xfail works as expected. (probably I'll do it tomorrow evening)

[fcharras]

Looks like the tests in the red pipeline actually passed, but the publishing step failed, not related to the PR.

[EdAbati]

I tested with cupy and it is all green with array_api_compat<1.5 ✅

FYI it seems there is an issue with array_api_compat==1.5 (but now fixed in main)

xp.asarraydoesn't convert the array when xp == 'array_api_compat.cupy' and the array is a numpy.ndarray:

>>> import numpy as np
>>> import array_api_compat.cupy as xp
>>> a = np.asarray([1,2,3])
>>> l = [1,2,3]
>>> type(xp.asarray(a))
<class 'numpy.ndarray'>
>>> type(xp.asarray(l))
<class 'cupy.ndarray'>

Testing with array_api_compat==1.5:

FAILED sklearn/metrics/tests/test_common.py::test_array_api_compliance[mean_absolute_error-check_array_api_multioutput_regression_metric-cupy-None-None] - AttributeError: 'numpy.ndarray' object has no attribute 'get'

I see the same error when running the tests on the new _average function.

[ogrisel]

FYI it seems there is an issue with array_api_compat==1.5 (but now fixed in main)

Since we don't have a cupy CI yet, we can just assume an array-api-compat version with the fix will be out before it bothers our CI :)

But if that's the case, maybe we can spend some effort to skip cupy tests when array_api_compat's version is one of the known versions with the bug.

[ogrisel]

LGTM otherwise. Thanks for the PR.

[EdAbati]

Hey @glemaitre sorry for the ping, I noticed you are the other reviewer :) I was wondering if there is anything I should change in this PR

[ogrisel]

Maybe @OmarManzoor would be interested in reviewing this one as well :)

[OmarManzoor]

Thanks for the PR @EdAbati. Could you kindly resolve the conflict?

[OmarManzoor]

Just a few comments regarding the change log, otherwise looks good.

[OmarManzoor]

LGTM. Thanks @EdAbati!

[EdAbati]

Thank you both 🙂