Merge branch '598-marginalized-parameter-reconstruction-broken' into 'master'

Resolve "Marginalized parameter reconstruction broken"

Closes #598

See merge request lscsoft/bilby!1016

bilby/gw/conversion.py

@@ -244,19 +244,28 @@ def convert_to_lal_binary_black_hole_parameters(parameters):
                     converted_parameters[key])
                 converted_parameters['cos_tilt_{}'.format(idx)] = \
                     np.sign(converted_parameters[key])
-                converted_parameters['phi_jl'] = 0.0
-                converted_parameters['phi_12'] = 0.0
             else:
-                converted_parameters[f"cos_tilt_{idx}"] = (
-                    converted_parameters[key] / converted_parameters[f"a_{idx}"]
-                )
+                with np.errstate(invalid="raise"):
+                    try:
+                        converted_parameters[f"cos_tilt_{idx}"] = (
+                            converted_parameters[key] / converted_parameters[f"a_{idx}"]
+                        )
+                    except (FloatingPointError, ZeroDivisionError):
+                        logger.debug(
+                            "Error in conversion to spherical spin tilt. "
+                            "This is often due to the spin parameters being zero. "
+                            f"Setting cos_tilt_{idx} = 1."
+                        )
+                        converted_parameters[f"cos_tilt_{idx}"] = 1.0
+
+    for key in ["phi_jl", "phi_12"]:
+        if key not in converted_parameters:
+            converted_parameters[key] = 0.0
 
     for angle in ['tilt_1', 'tilt_2', 'theta_jn']:
         cos_angle = str('cos_' + angle)
         if cos_angle in converted_parameters.keys():
-            with np.errstate(invalid="ignore"):
-                converted_parameters[angle] =\
-                    np.arccos(converted_parameters[cos_angle])
+            converted_parameters[angle] = np.arccos(converted_parameters[cos_angle])
 
     if "delta_phase" in original_keys:
         with np.errstate(invalid="ignore"):
@@ -782,6 +791,7 @@ def _generate_all_cbc_parameters(sample, defaults, base_conversion,
             logger.debug('Assuming {} = {}'.format(key, default))
 
     output_sample = fill_from_fixed_priors(output_sample, priors)
+    output_sample, _ = base_conversion(output_sample)
     if likelihood is not None:
         if (
                 hasattr(likelihood, 'phase_marginalization') or
@@ -820,7 +830,6 @@ def _generate_all_cbc_parameters(sample, defaults, base_conversion,
                 )
     if likelihood is not None:
         compute_snrs(output_sample, likelihood)
-    output_sample, _ = base_conversion(output_sample)
     for key, func in zip(["mass", "spin", "source frame"], [
             generate_mass_parameters, generate_spin_parameters,
             generate_source_frame_parameters]):

test/gw/conversion_test.py

@@ -296,6 +296,55 @@ class TestConvertToLALParams(unittest.TestCase):
             dict(a_1=a_1, tilt_1=tilt_1, phi_jl=phi_jl, phi_12=phi_12),
         )
 
+    def test_bbh_zero_aligned_spin_to_spherical_with_magnitude(self):
+        """
+        Test the the conversion returns the correct tilt angles when zero
+        aligned spin is passed if the magnitude is also pass.
+
+        If the magnitude is zero this returns tilt = 0.
+        If the magnitude is non-zero this returns tilt = pi.
+        """
+        self.parameters["chi_1"] = 0
+        self.parameters["chi_2"] = 0
+        a_1 = 0
+        self.parameters["a_1"] = a_1
+        a_2 = 1
+        self.parameters["a_2"] = a_2
+        tilt_1 = 0
+        tilt_2 = np.pi / 2
+        phi_jl = 0
+        phi_12 = 0
+        self.bbh_convert()
+        self.assertDictEqual(
+            {
+                key: self.parameters[key]
+                for key in ["a_1", "a_2", "tilt_1", "tilt_2", "phi_12", "phi_jl"]
+            },
+            dict(a_1=a_1, a_2=a_2, tilt_1=tilt_1, tilt_2=tilt_2, phi_jl=phi_jl, phi_12=phi_12),
+        )
+
+    def test_bbh_zero_aligned_spin_to_spherical_without_magnitude(self):
+        """
+        Test the the conversion returns the correct tilt angles when zero
+        aligned spin is passed if the magnitude is also pass.
+
+        If the magnitude is zero this returns tilt = 0.
+        If the magnitude is non-zero this returns tilt = pi.
+        """
+        self.parameters["chi_1"] = 0
+        a_1 = 0
+        tilt_1 = np.pi / 2
+        phi_jl = 0
+        phi_12 = 0
+        self.bbh_convert()
+        self.assertDictEqual(
+            {
+                key: self.parameters[key]
+                for key in ["a_1", "tilt_1", "phi_12", "phi_jl"]
+            },
+            dict(a_1=a_1, tilt_1=tilt_1, phi_jl=phi_jl, phi_12=phi_12),
+        )
+
     def test_bbh_cos_angle_to_angle_conversion(self):
         self.parameters["cos_tilt_1"] = 1
         t1 = np.arccos(self.parameters["cos_tilt_1"])