ENH Array API for chi2_kernel (#29267)

Tialo · EdAbati · web-flow · commit fa65654d0f31 · 2024-06-20T11:45:53.000+02:00
Co-authored-by: Edoardo Abati &lt;29585319+EdAbati@users.noreply.github.com&gt;
diff --git a/doc/modules/array_api.rst b/doc/modules/array_api.rst
@@ -121,6 +121,7 @@ Metrics
 - :func:`sklearn.metrics.mean_squared_error`
 - :func:`sklearn.metrics.mean_tweedie_deviance`
 - :func:`sklearn.metrics.pairwise.additive_chi2_kernel`
+- :func:`sklearn.metrics.pairwise.chi2_kernel`
 - :func:`sklearn.metrics.pairwise.cosine_similarity`
 - :func:`sklearn.metrics.pairwise.paired_cosine_distances`
 - :func:`sklearn.metrics.r2_score`
diff --git a/doc/whats_new/v1.6.rst b/doc/whats_new/v1.6.rst
@@ -41,6 +41,7 @@ See :ref:`array_api` for more details.
 - :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>`;
+- :func:`sklearn.metrics.pairwise.chi2_kernel` :pr:`29267` by :user:`Yaroslav Korobko <Tialo>`;
 - :func:`sklearn.metrics.pairwise.cosine_similarity` :pr:`29014` by :user:`Edoardo Abati <EdAbati>`;
 - :func:`sklearn.metrics.pairwise.paired_cosine_distances` :pr:`29112` by :user:`Edoardo Abati <EdAbati>`.
 
diff --git a/sklearn/metrics/pairwise.py b/sklearn/metrics/pairwise.py
@@ -1828,9 +1828,12 @@ def chi2_kernel(X, Y=None, gamma=1.0):
     array([[0.36..., 0.13...],
            [0.13..., 0.36...]])
     """
+    xp, _ = get_namespace(X, Y)
     K = additive_chi2_kernel(X, Y)
     K *= gamma
-    return np.exp(K, K)
+    if _is_numpy_namespace(xp):
+        return np.exp(K, out=K)
+    return xp.exp(K)
 
 
 # Helper functions - distance
diff --git a/sklearn/metrics/tests/test_common.py b/sklearn/metrics/tests/test_common.py
@@ -53,6 +53,7 @@
 from sklearn.metrics._base import _average_binary_score
 from sklearn.metrics.pairwise import (
     additive_chi2_kernel,
+    chi2_kernel,
     cosine_similarity,
     paired_cosine_distances,
 )
@@ -1979,6 +1980,7 @@ def check_array_api_metric_pairwise(metric, array_namespace, device, dtype_name)
     additive_chi2_kernel: [check_array_api_metric_pairwise],
     mean_gamma_deviance: [check_array_api_regression_metric],
     max_error: [check_array_api_regression_metric],
+    chi2_kernel: [check_array_api_metric_pairwise],
 }
 
 

Original file line number	Diff line number	Diff line change
`@@ -53,6 +53,7 @@`
`53`	`53`	`from sklearn.metrics._base import _average_binary_score`
`54`	`54`	`from sklearn.metrics.pairwise import (`
`55`	`55`	`additive_chi2_kernel,`
	`56`	`+ chi2_kernel,`
`56`	`57`	`cosine_similarity,`
`57`	`58`	`paired_cosine_distances,`
`58`	`59`	`)`
`@@ -1979,6 +1980,7 @@ def check_array_api_metric_pairwise(metric, array_namespace, device, dtype_name)`
`1979`	`1980`	`additive_chi2_kernel: [check_array_api_metric_pairwise],`
`1980`	`1981`	`mean_gamma_deviance: [check_array_api_regression_metric],`
`1981`	`1982`	`max_error: [check_array_api_regression_metric],`
	`1983`	`+ chi2_kernel: [check_array_api_metric_pairwise],`
`1982`	`1984`	`}`
`1983`	`1985`
`1984`	`1986`