fix(families): raise ValueError for x outside support in exponential and uniform

Author: MyznikovFD

src/pysatl_core/families/builtins/continuous/exponential.py

@@ -233,8 +233,7 @@ def _base_score(parameters: Parametrization, x: NumericArray) -> NumericArray:
         The derivative with respect to λ is:
             ∂/∂λ log f = 1/λ - x   (for x ≥ 0).
 
-        For points x < 0 the density is zero; we return 0 for numerical stability
-        (though the score is technically undefined there).
+        For points x < 0 the density is zero; we return ValueError.
 
         Parameters
         ----------
@@ -251,9 +250,10 @@ def _base_score(parameters: Parametrization, x: NumericArray) -> NumericArray:
         """
         params = cast(_Rate, parameters)
         lam = params.lambda_
-        inside = x >= 0
-        grad = np.where(inside, 1.0 / lam - x, 0.0)
-        return grad[..., np.newaxis]  # shape (..., 1)
+        if np.any(x < 0):
+            raise ValueError(f"Score is undefined for x < 0 (outside support). Got x = {x}")
+        grad = 1.0 / lam - x
+        return grad[..., np.newaxis]
 
     Exponential = ParametricFamily(
         name=FamilyName.EXPONENTIAL,

src/pysatl_core/families/builtins/continuous/uniform.py

@@ -272,8 +272,7 @@ def _base_score(parameters: Parametrization, x: NumericArray) -> NumericArray:
             ∂/∂a log f =  1/(b - a)
             ∂/∂b log f = -1/(b - a)
 
-        For points outside the support, the gradient is set to 0 (since density is zero,
-        but the score is typically considered undefined; we return 0 for numerical safety).
+        For points outside the support, there is ValueError.
 
         Parameters
         ----------
@@ -291,11 +290,12 @@ def _base_score(parameters: Parametrization, x: NumericArray) -> NumericArray:
         params = cast(_Standard, parameters)
         a = params.lower_bound
         b = params.upper_bound
-        width = b - a
+        if np.any((x < a) | (x > b)):
+            raise ValueError(f"Score is undefined for x outside support [{a}, {b}]. Got x = {x}")
 
-        inside = (x >= a) & (x <= b)
-        grad_a = np.where(inside, 1.0 / width, 0.0)
-        grad_b = np.where(inside, -1.0 / width, 0.0)
+        width = b - a
+        grad_a = np.full_like(x, 1.0 / width)
+        grad_b = np.full_like(x, -1.0 / width)
         return np.stack([grad_a, grad_b], axis=-1)
 
     Uniform = ParametricFamily(

src/pysatl_core/families/parametric_family.py

@@ -438,6 +438,9 @@ def score(self, parameters: Parametrization, x: NumericArray) -> NumericArray:
         NumericArray
             Gradient with respect to the parameters of the given parametrization.
             Shape is (..., d), where d is the number of parameters of the parametrization.
+
+        ValueError
+            If any value in `x` lies outside the distribution's support.
         """
         if self._base_score is None:
             raise ValueError(

tests/unit/families/builtins/continuous/test_exponential.py

@@ -273,6 +273,13 @@ def test_score_shape(self, parametrization_name, params):
         assert grad.shape == (len(x), 1)
         assert grad.dtype == float
 
+    def test_score_raises_for_x_outside_support(self):
+        lam = 0.5
+        dist = self.exponential_family(lambda_=lam)
+        x_bad = np.array([-0.1, -1.0])
+        with pytest.raises(ValueError, match="Score is undefined for x < 0"):
+            dist.family.score(dist.parametrization, x_bad)
+
 
 class TestExponentialFamilyEdgeCases(BaseDistributionTest):
     """Test edge cases and error conditions for exponential distribution."""

tests/unit/families/builtins/continuous/test_uniform.py

@@ -248,32 +248,28 @@ def test_score_standard_parametrization(self):
         """Test SCORE for standard parametrization against analytical formula."""
         a, b = 2.0, 5.0
         dist = self.uniform_family(lower_bound=a, upper_bound=b)
-        x = np.array([1.0, 2.0, 3.5, 5.0, 6.0])
+        x = np.array([2.0, 3.5, 5.0])
         grad = dist.family.score(dist.parametrization, x)
 
         width = b - a
-        inside = (x >= a) & (x <= b)
-        expected = np.stack(
-            [np.where(inside, 1.0 / width, 0.0), np.where(inside, -1.0 / width, 0.0)], axis=-1
-        )
+        expected = np.tile([1.0 / width, -1.0 / width], (len(x), 1))
 
         np.testing.assert_allclose(grad, expected, rtol=self.CALCULATION_PRECISION)
 
     def test_score_meanWidth_parametrization(self):
         """Test SCORE for meanWidth parametrization via chain rule."""
         mean, width = 3.5, 3.0  # corresponds to a=2, b=5
         dist = self.uniform_family(parametrization_name="meanWidth", mean=mean, width=width)
-        x = np.array([1.0, 2.0, 3.5, 5.0, 6.0])
+        x = np.array([2.0, 3.5, 5.0])
         grad = dist.family.score(dist.parametrization, x)
 
-        a, b = 2.0, 5.0
-        inside = (x >= a) & (x <= b)
-        base_grad_a = np.where(inside, 1.0 / 3.0, 0.0)
-        base_grad_b = np.where(inside, -1.0 / 3.0, 0.0)
+        _a, _b = 2.0, 5.0
+        base_grad_a = 1.0 / 3.0
+        base_grad_b = -1.0 / 3.0
         # Transform to (mean, width)
         expected_mean = 0.5 * (base_grad_a + base_grad_b)
         expected_width = -base_grad_a + base_grad_b
-        expected = np.stack([expected_mean, expected_width], axis=-1)
+        expected = np.tile([expected_mean, expected_width], (len(x), 1))
 
         np.testing.assert_allclose(grad, expected, rtol=self.CALCULATION_PRECISION)
 
@@ -283,17 +279,16 @@ def test_score_minRange_parametrization(self):
         dist = self.uniform_family(
             parametrization_name="minRange", minimum=minimum, range_val=range_val
         )
-        x = np.array([1.0, 2.0, 3.5, 5.0, 6.0])
+        x = np.array([2.0, 3.5, 5.0])
         grad = dist.family.score(dist.parametrization, x)
 
-        a, b = 2.0, 5.0
-        inside = (x >= a) & (x <= b)
-        base_grad_a = np.where(inside, 1.0 / 3.0, 0.0)
-        base_grad_b = np.where(inside, -1.0 / 3.0, 0.0)
+        _a, _b = 2.0, 5.0
+        base_grad_a = 1.0 / 3.0
+        base_grad_b = -1.0 / 3.0
         # Transform to (minimum, range_val)
         expected_min = base_grad_a
         expected_range = -base_grad_a + base_grad_b
-        expected = np.stack([expected_min, expected_range], axis=-1)
+        expected = np.tile([expected_min, expected_range], (len(x), 1))
 
         np.testing.assert_allclose(grad, expected, rtol=self.CALCULATION_PRECISION)
 
@@ -327,12 +322,19 @@ def logpdf_b(b_val: float) -> float:
     )
     def test_score_shape(self, parametrization_name, params):
         """Test SCORE shape for all uniform parametrizations."""
-        x = np.array([1.0, 2.0, 3.5, 5.0, 6.0])
+        x = np.array([2.0, 3.5, 5.0])
         dist = self.uniform_family(parametrization_name=parametrization_name, **params)
         grad = dist.family.score(dist.parametrization, x)
         assert grad.shape == (len(x), 2)
         assert grad.dtype == float
 
+    def test_score_raises_for_x_outside_support(self):
+        a, b = 2.0, 5.0
+        dist = self.uniform_family(lower_bound=a, upper_bound=b)
+        x_bad = np.array([1.0, 6.0])
+        with pytest.raises(ValueError, match="Score is undefined for x outside support"):
+            dist.family.score(dist.parametrization, x_bad)
+
 
 class TestUniformFamilyEdgeCases(BaseDistributionTest):
     """Test edge cases and error conditions for uniform distribution."""