FIX RuntimeWarning by dividing by zero in test_iforest_with_uniform_data (#19622)

LSturtew · web-flow · commit 302106bcac44 · 2021-03-15T20:00:14.000+01:00
diff --git a/sklearn/ensemble/_iforest.py b/sklearn/ensemble/_iforest.py
@@ -450,11 +450,14 @@ def _compute_score_samples(self, X, subsample_features):
                 + _average_path_length(n_samples_leaf)
                 - 1.0
             )
-
+        denominator = (
+            len(self.estimators_) * _average_path_length([self.max_samples_])
+        )
         scores = 2 ** (
-            -depths
-            / (len(self.estimators_)
-               * _average_path_length([self.max_samples_]))
+            # For a single training sample, denominator and depth are 0.
+            # Therefore, we set the score manually to 1.
+            -np.divide(depths, denominator, out=np.ones_like(depths),
+                       where=denominator != 0)
         )
         return scores
 
