add entropy feature

tensorflow_privacy/privacy/membership_inference_attack/data_structures.py

@@ -22,6 +22,7 @@ from dataclasses import dataclass
 import numpy as np
 import pandas as pd
 from sklearn import metrics
+from scipy import special
 
 
 ENTIRE_DATASET_SLICE_STR = 'SingleSliceSpec(Entire dataset)'
@@ -144,6 +145,9 @@ def _is_np_array(arr, arr_name):
   if arr is not None and not isinstance(arr, np.ndarray):
     raise ValueError('%s should be a numpy array.' % arr_name)
 
+def _log_value(probs, small_value=1e-30):
+  """Compute the log value on the probability. Clip the probability in case it is close to 0"""
+  return -np.log(np.maximum(probs, small_value))
 
 @dataclass
 class AttackInputData:
@@ -165,6 +169,11 @@ class AttackInputData:
   loss_train: np.ndarray = None
   loss_test: np.ndarray = None
 
+  # Explicitly specified prediction entropy. If provided, this is used instead of deriving
+  # entropy from logits and labels (https://arxiv.org/pdf/2003.10595.pdf by Song and Mittal)
+  entropy_train: np.ndarray = None
+  entropy_test: np.ndarray = None
+
   @property
   def num_classes(self):
     if self.labels_train is None or self.labels_test is None:
@@ -177,6 +186,34 @@ class AttackInputData:
   def _get_loss(logits: np.ndarray, true_labels: np.ndarray):
     return logits[range(logits.shape[0]), true_labels]
 
+  @staticmethod
+  def _get_entropy(logits: np.ndarray, true_labels: np.ndarray):
+    if (np.absolute(np.sum(logits,axis=1)-1)<=1e-3).all():
+      probs = logits
+    else:
+      """Using softmax to compute probability from logits"""
+      probs = special.softmax(logits, axis=1)
+    if true_labels is None:
+      '''
+      When not given ground truth label, we compute the normal prediction entropy.
+      See the Equation (7) in https://arxiv.org/pdf/2003.10595.pdf
+      '''
+      return np.sum(np.multiply(probs, _log_value(probs)),axis=1)
+    else:
+      '''
+      When given the groud truth label, we compute the modified prediction entropy.
+      See the Equation (8) in https://arxiv.org/pdf/2003.10595.pdf
+      '''
+      log_probs = _log_value(probs)
+      reverse_probs = 1-probs
+      log_reverse_probs = _log_value(reverse_probs)
+      modified_probs = np.copy(probs)
+      modified_probs[range(true_labels.size), true_labels] = reverse_probs[range(true_labels.size), true_labels]
+      modified_log_probs = np.copy(log_reverse_probs)
+      modified_log_probs[range(true_labels.size), true_labels] = log_probs[range(true_labels.size), true_labels]
+      return np.sum(np.multiply(modified_probs, modified_log_probs),axis=1)
+    
+
   def get_loss_train(self):
     """Calculates cross-entropy losses for the training set."""
     if self.loss_train is not None:
@@ -189,6 +226,18 @@ class AttackInputData:
       return self.loss_test
     return self._get_loss(self.logits_test, self.labels_test)
 
+  def get_entropy_train(self):
+    """Calculates prediction entropy for the training set."""
+    if self.entropy_train is not None:
+      return self.entropy_train
+    return self._get_entropy(self.logits_train, self.labels_train)
+
+  def get_entropy_test(self):
+    """Calculates prediction entropy for the test set."""
+    if self.entropy_test is not None:
+      return self.entropy_test
+    return self._get_entropy(self.logits_test, self.labels_test)
+
   def get_train_size(self):
     """Returns size of the training set."""
     if self.loss_train is not None:
@@ -207,6 +256,10 @@ class AttackInputData:
       raise ValueError(
           'loss_test and loss_train should both be either set or unset')
     
+    if (self.entropy_train is None) != (self.entropy_test is None):
+      raise ValueError(
+          'entropy_test and entropy_train should both be either set or unset')
+
     if (self.logits_train is None) != (self.logits_test is None):
       raise ValueError(
           'logits_train and logits_test should both be either set or unset')
@@ -216,8 +269,8 @@ class AttackInputData:
           'labels_train and labels_test should both be either set or unset')
 
     if (self.labels_train is None and self.loss_train is None and
-        self.logits_train is None):
-      raise ValueError('At least one of labels, logits or losses should be set')
+        self.logits_train is None and self.entropy_train is None):
+      raise ValueError('At least one of labels, logits, losses or entropy should be set')
 
     if self.labels_train is not None and not _is_integer_type_array(
         self.labels_train):
@@ -233,11 +286,15 @@ class AttackInputData:
     _is_np_array(self.labels_test, 'labels_test')
     _is_np_array(self.loss_train, 'loss_train')
     _is_np_array(self.loss_test, 'loss_test')
+    _is_np_array(self.entropy_train, 'entropy_train')
+    _is_np_array(self.entropy_test, 'entropy_test')
 
     _is_last_dim_equal(self.logits_train, 'logits_train', self.logits_test,
                        'logits_test')
     _is_array_one_dimensional(self.loss_train, 'loss_train')
     _is_array_one_dimensional(self.loss_test, 'loss_test')
+    _is_array_one_dimensional(self.entropy_train, 'entropy_train')
+    _is_array_one_dimensional(self.entropy_test, 'entropy_test')
     _is_array_one_dimensional(self.labels_train, 'labels_train')
     _is_array_one_dimensional(self.labels_test, 'labels_test')
 
@@ -246,6 +303,8 @@ class AttackInputData:
     result = ['AttackInputData(']
     _append_array_shape(self.loss_train, 'loss_train', result)
     _append_array_shape(self.loss_test, 'loss_test', result)
+    _append_array_shape(self.entropy_train, 'entropy_train', result)
+    _append_array_shape(self.entropy_test, 'entropy_test', result)
     _append_array_shape(self.logits_train, 'logits_train', result)
     _append_array_shape(self.logits_test, 'logits_test', result)
     _append_array_shape(self.labels_train, 'labels_train', result)