Merge pull request cupy#8343 from ev-br/upd_rbf_tests

MAINT: interpolate: update RBF to scipy 1.13

cupyx/scipy/interpolate/_rbfinterp.py

@@ -640,7 +640,7 @@ def __init__(self, y, d,
             degree = int(degree)
             if degree < -1:
                 raise ValueError("`degree` must be at least -1.")
-            elif degree < min_degree:
+            elif -1 < degree < min_degree:
                 warnings.warn(
                     f"`degree` should not be below {min_degree} when `kernel` "
                     f"is '{kernel}'. The interpolant may not be uniquely "

tests/cupyx_tests/scipy_tests/interpolate_tests/test_rbfinterp.py

@@ -384,7 +384,8 @@ def test_not_enough_observations_error(self, xp, scp):
     @testing.with_requires("scipy<1.13")
     @testing.numpy_cupy_allclose(scipy_name='scp', accept_error=UserWarning)
     @pytest.mark.parametrize('kernel',
-                             [kl for kl in _NAME_TO_MIN_DEGREE])
+                             [kl for kl in _NAME_TO_MIN_DEGREE
+                              if _NAME_TO_MIN_DEGREE[kl] >= 1])
     def test_degree_warning(self, xp, scp, kernel):
         y = xp.linspace(0, 1, 5)[:, None]
         d = xp.zeros(5)
@@ -393,6 +394,15 @@ def test_degree_warning(self, xp, scp, kernel):
             warnings.simplefilter("error")
             self.build(scp, y, d, epsilon=1.0, kernel=kernel, degree=deg-1)
 
+    @pytest.mark.parametrize('kernel', [kl for kl in _NAME_TO_MIN_DEGREE])
+    @testing.numpy_cupy_allclose(scipy_name='scp')
+    def test_minus_one_degree(self, xp, scp, kernel):
+        # Make sure a degree of -1 is accepted without any warning.
+        y = xp.linspace(0, 1, 5)[:, None]
+        d = xp.zeros(5)
+        f = self.build(scp, y, d, epsilon=1.0, kernel=kernel, degree=-1)
+        return f(y)
+
     @testing.numpy_cupy_allclose(scipy_name='scp', accept_error=LinAlgError)
     def test_rank_error(self, xp, scp):
         # An error should be raised when `kernel` is "thin_plate_spline" and