scikit-learn · OmarManzoor · Jul 23, 2024 · Jun 10, 2024 · Jun 13, 2024 · Jun 13, 2024
diff --git a/.github/workflows/cuda-ci.yml b/.github/workflows/cuda-ci.yml
@@ -42,4 +42,4 @@ jobs:
         run: |
           source "${HOME}/conda/etc/profile.d/conda.sh"
           conda activate sklearn
-          pytest -k 'array_api'
+          SCIPY_ARRAY_API=1 pytest -k 'array_api'
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
@@ -138,6 +138,7 @@ jobs:
         # Here we make sure, that they are still run on a regular basis.
         ${{ if eq(variables['Build.Reason'], 'Schedule') }}:
           SKLEARN_SKIP_NETWORK_TESTS: '0'
+        SCIPY_ARRAY_API: '1'
 
 # Check compilation with Ubuntu 22.04 LTS (Jammy Jellyfish) and scipy from conda-forge
 # By default the CI is sequential, where `Ubuntu_Jammy_Jellyfish` runs first and
@@ -221,6 +222,7 @@ jobs:
         # makes sure that they are single threaded in each xdist subprocess.
         PYTEST_XDIST_VERSION: 'none'
         PIP_BUILD_ISOLATION: 'true'
+        SCIPY_ARRAY_API: '1'
 
 - template: build_tools/azure/posix-docker.yml
   parameters:
@@ -259,6 +261,7 @@ jobs:
         DISTRIB: 'conda'
         LOCK_FILE: './build_tools/azure/pylatest_conda_forge_mkl_osx-64_conda.lock'
         SKLEARN_TESTS_GLOBAL_RANDOM_SEED: '5'  # non-default seed
+        SCIPY_ARRAY_API: '1'
       pylatest_conda_mkl_no_openmp:
         DISTRIB: 'conda'
         LOCK_FILE: './build_tools/azure/pylatest_conda_mkl_no_openmp_osx-64_conda.lock'

diff --git a/doc/modules/array_api.rst b/doc/modules/array_api.rst
@@ -119,6 +119,7 @@ Metrics
 - :func:`sklearn.metrics.mean_absolute_error`
 - :func:`sklearn.metrics.mean_absolute_percentage_error`
 - :func:`sklearn.metrics.mean_gamma_deviance`
+- :func:`sklearn.metrics.mean_poisson_deviance` (requires `enabling array API support for SciPy <https://docs.scipy.org/doc/scipy/dev/api-dev/array_api.html#using-array-api-standard-support>`_)
 - :func:`sklearn.metrics.mean_squared_error`
 - :func:`sklearn.metrics.mean_tweedie_deviance`
 - :func:`sklearn.metrics.pairwise.additive_chi2_kernel`

diff --git a/doc/whats_new/v1.6.rst b/doc/whats_new/v1.6.rst
@@ -39,6 +39,7 @@ See :ref:`array_api` for more details.
   and :pr:`29143` by :user:`Tialo <Tialo>` and :user:`Loïc Estève <lesteve>`;
 - :func:`sklearn.metrics.mean_absolute_percentage_error` :pr:`29300` by :user:`Emily Chen <EmilyXinyi>`;
 - :func:`sklearn.metrics.mean_gamma_deviance` :pr:`29239` by :user:`Emily Chen <EmilyXinyi>`;
+- :func:`sklearn.metrics.mean_poisson_deviance` :pr:`29227` by :user:`Emily Chen <EmilyXinyi>`;
 - :func:`sklearn.metrics.mean_squared_error` :pr:`29142` by :user:`Yaroslav Korobko <Tialo>`;
 - :func:`sklearn.metrics.mean_tweedie_deviance` :pr:`28106` by :user:`Thomas Li <lithomas1>`;
 - :func:`sklearn.metrics.pairwise.additive_chi2_kernel` :pr:`29144` by :user:`Yaroslav Korobko <Tialo>`;

diff --git a/sklearn/metrics/tests/test_common.py b/sklearn/metrics/tests/test_common.py
@@ -76,7 +76,7 @@
     assert_array_less,
     ignore_warnings,
 )
-from sklearn.utils.fixes import COO_CONTAINERS
+from sklearn.utils.fixes import COO_CONTAINERS, parse_version, sp_version
 from sklearn.utils.multiclass import type_of_target
 from sklearn.utils.validation import _num_samples, check_random_state
 
@@ -1867,6 +1867,12 @@ def check_array_api_multilabel_classification_metric(
 
 
 def check_array_api_regression_metric(metric, array_namespace, device, dtype_name):
+    func_name = metric.func.__name__ if isinstance(metric, partial) else metric.__name__
+    if func_name == "mean_poisson_deviance" and sp_version < parse_version("1.14.0"):
+        pytest.skip(
+            "mean_poisson_deviance's dependency `xlogy` is available as of scipy 1.14.0"
+        )
+
     y_true_np = np.array([2.0, 0.1, 1.0, 4.0], dtype=dtype_name)
     y_pred_np = np.array([0.5, 0.5, 2, 2], dtype=dtype_name)
 
@@ -2012,6 +2018,7 @@ def check_array_api_metric_pairwise(metric, array_namespace, device, dtype_name)
         check_array_api_regression_metric,
     ],
     paired_cosine_distances: [check_array_api_metric_pairwise],
+    mean_poisson_deviance: [check_array_api_regression_metric],
     additive_chi2_kernel: [check_array_api_metric_pairwise],
     mean_gamma_deviance: [check_array_api_regression_metric],
     max_error: [check_array_api_regression_metric],

diff --git a/sklearn/utils/_array_api.py b/sklearn/utils/_array_api.py
@@ -5,6 +5,8 @@
 
 import itertools
 import math
+import os
+import warnings
 from functools import wraps
 
 import numpy
@@ -106,6 +108,17 @@ def _check_array_api_dispatch(array_api_dispatch):
                 f"NumPy must be {min_numpy_version} or newer to dispatch array using"
                 " the API specification"
             )
+        if os.environ.get("SCIPY_ARRAY_API") != "1":
+            warnings.warn(
+                (
+                    "Some scikit-learn array API features might rely on enabling "
+                    "SciPy's own support for array API to function properly. "
+                    "Please set the SCIPY_ARRAY_API=1 environment variable "
+                    "before importing sklearn or scipy. More details at: "
+                    "https://docs.scipy.org/doc/scipy/dev/api-dev/array_api.html"
+                ),
+                UserWarning,
+            )
 
 
 def _single_array_device(array):

diff --git a/sklearn/utils/tests/test_array_api.py b/sklearn/utils/tests/test_array_api.py
@@ -1,3 +1,4 @@
+import os
 import re
 from functools import partial
 
@@ -77,7 +78,7 @@ def test_get_namespace_ndarray_with_dispatch():
 
 
 @skip_if_array_api_compat_not_configured
-def test_get_namespace_array_api():
+def test_get_namespace_array_api(monkeypatch):
     """Test get_namespace for ArrayAPI arrays."""
     xp = pytest.importorskip("array_api_strict")
 
@@ -90,6 +91,18 @@ def test_get_namespace_array_api():
         with pytest.raises(TypeError):
             xp_out, is_array_api_compliant = get_namespace(X_xp, X_np)
 
+        def mock_getenv(key):
+            if key == "SCIPY_ARRAY_API":
+                return "0"
+
+        monkeypatch.setattr("os.environ.get", mock_getenv)
+        assert os.environ.get("SCIPY_ARRAY_API") != "1"
+        with pytest.warns(
+            UserWarning,
+            match="enabling SciPy's own support for array API to function properly. ",
+        ):
+            xp_out, is_array_api_compliant = get_namespace(X_xp)
+
 
 class _AdjustableNameAPITestWrapper(_ArrayAPIWrapper):
     """API wrapper that has an adjustable name. Used for testing."""