- Add bound to HyperGeometric logp

- Pass unit tests when scipy logpmf returns nan

Author: ricardoV94

pymc3/distributions/discrete.py

@@ -930,7 +930,9 @@ def logp(self, value):
             - betaln(n - value + 1, bad - n + value + 1)
             - betaln(tot + 1, 1)
         )
-        return result
+        lower = tt.max([0, n - N + k])
+        upper = tt.min([k, n])
+        return bound(result, lower <= value, value <= upper)
 
 
 class DiscreteUniform(Discrete):

pymc3/tests/test_distributions.py

@@ -805,11 +805,15 @@ def test_geometric(self):
         )
 
     def test_hypergeometric(self):
+        def modified_scipy_hypergeom_logpmf(value, N, k, n):
+            original_res = sp.hypergeom.logpmf(value, N, k, n)
+            return original_res if not np.isnan(original_res) else -np.inf
+
         self.pymc3_matches_scipy(
             HyperGeometric,
             Nat,
             {"N": NatSmall, "k": NatSmall, "n": NatSmall},
-            lambda value, N, k, n: sp.hypergeom.logpmf(value, N, k, n),
+            lambda value, N, k, n: modified_scipy_hypergeom_logpmf(value, N, k, n),
         )
 
     def test_negative_binomial(self):