Merge pull request #515 from PyAutoLabs/feature/sersic-core-effective-radius-zero

fix: SersicCore.intensity_prime ZeroDivisionError on effective_radius=0 (#514)

Author: Jammy2211

autogalaxy/profiles/light/standard/sersic_core.py

@@ -64,9 +64,9 @@ def intensity_prime(self, xp=np) -> float:
             * (2.0 ** (-self.gamma / self.alpha))
             * xp.exp(
                 self.sersic_constant
-                * (
-                    ((2.0 ** (1.0 / self.alpha)) * self.radius_break)
-                    / self.effective_radius
+                * xp.divide(
+                    (2.0 ** (1.0 / self.alpha)) * self.radius_break,
+                    self.effective_radius,
                 )
                 ** (1.0 / self.sersic_index)
             )

test_autogalaxy/profiles/light/standard/test_sersic_core.py

@@ -1,4 +1,5 @@
 from __future__ import division, print_function
+import numpy as np
 import pytest
 
 import autogalaxy as ag
@@ -22,6 +23,28 @@ def test__image_2d_from__elliptical__ell_comps_nonzero__correct_value():
     assert image == pytest.approx(0.0255173, 1.0e-4)
 
 
+def test__intensity_prime__effective_radius_zero__non_finite_not_zero_division():
+    # A degenerate `effective_radius=0` (e.g. a non-linear search proposing an
+    # unphysical value, or a wavelength-relation instance evaluating to 0) must
+    # yield a non-finite value the search resamples on, not a hard
+    # ``ZeroDivisionError`` — matching every other profile's array division.
+    lp = ag.lp.SersicCore(
+        effective_radius=0.0,
+        sersic_index=4.0,
+        radius_break=0.01,
+        intensity=0.1,
+        gamma=1.0,
+        alpha=1.0,
+    )
+
+    value = lp.intensity_prime()
+
+    assert not np.isfinite(value)
+
+    # The full image path must not raise either.
+    lp.image_2d_from(grid=ag.Grid2DIrregular([[0.0, 0.1]]))
+
+
 def test__image_2d_from__spherical_profile__matches_elliptical_with_zero_ellipticity():
     elliptical = ag.lp.SersicCore(
         ell_comps=(0.0, 0.0),