Merge pull request #2327 from f4str/activation-defense-bug

Fix `ActivationDefense` and `SpectralSignatures` expected flattened bug

Author: beat-buesser

art/defences/detector/poison/activation_defence.py

@@ -695,7 +695,9 @@ def _get_activations(self, x_train: Optional[np.ndarray] = None) -> np.ndarray:
 
         # wrong way to get activations activations = self.classifier.predict(self.x_train)
         if isinstance(activations, np.ndarray):
-            nodes_last_layer = np.shape(activations)[1]
+            # flatten activations across batch
+            activations = np.reshape(activations, (activations.shape[0], -1))
+            nodes_last_layer = activations.shape[1]
         else:
             raise ValueError("activations is None or tensor.")
 

art/defences/detector/poison/spectral_signature_defense.py

@@ -121,6 +121,8 @@ def detect_poison(self, **kwargs) -> Tuple[dict, List[int]]:
             raise ValueError("Wrong type detected.")
 
         if features_x_poisoned is not None:
+            # flatten activations across batch
+            features_x_poisoned = np.reshape(features_x_poisoned, (features_x_poisoned.shape[0], -1))
             features_split = segment_by_class(features_x_poisoned, self.y_train, self.classifier.nb_classes)
         else:
             raise ValueError("Activation are `None`.")