Updated DIDI to only alphas > 0

Author: Simon-Rey

prefsampling/ordinal/didi.py

@@ -50,8 +50,8 @@ def didi(
             "Incorrect length of alphas vector. Should be equal to num_candidates."
         )
 
-    if not all(a >= 0 for a in alphas):
-        raise ValueError("The values of the alpha vector should all be positive.")
+    if not all(a > 0 for a in alphas):
+        raise ValueError("The values of the alpha vector should all be strictly positive.")
 
     rng = np.random.default_rng(seed)
 

tests/test_samplers/ordinal/test_ordinal_didi.py

@@ -9,4 +9,6 @@ def test_ordinal_did(self):
             didi(4, 5, alphas=[0.4, 0.4])
         with self.assertRaises(ValueError):
             didi(4, 5, alphas=[0.4, 0.4, 0.4, 0.4, -0.4])
-        didi(4, 5, alphas=[0, 0, 0, 0, 0])
+        with self.assertRaises(ValueError):
+            didi(4, 5, alphas=[0, 0, 0, 0, 0])
+        didi(4, 5, alphas=[0.1, 0.4, 0.8, 0.9, 1])