Merge pull request #1439 from rsepassi/adv_text

Updates to adversarial_text model

adversarial_text/adversarial_losses.py

@@ -83,8 +83,10 @@ def virtual_adversarial_loss(logits, embedded, inputs,
   """
   # Stop gradient of logits. See https://arxiv.org/abs/1507.00677 for details.
   logits = tf.stop_gradient(logits)
+  # Only care about the KL divergence on the final timestep.
   weights = _end_of_seq_mask(inputs.labels)
 
+  # Initialize perturbation with random noise.
   # shape(embedded) = (batch_size, num_timesteps, embedding_dim)
   d = _mask_by_length(tf.random_normal(shape=tf.shape(embedded)), inputs.length)
 
@@ -173,11 +175,15 @@ def _mask_by_length(t, length):
 
 def _scale_l2(x, norm_length):
   # shape(x) = (batch, num_timesteps, d)
-  x /= (1e-12 + tf.reduce_max(tf.abs(x), 2, keep_dims=True))
-  x_2 = tf.reduce_sum(tf.pow(x, 2), 2, keep_dims=True)
-  x /= tf.sqrt(1e-6 + x_2)
 
-  return norm_length * x
+  # Divide x by max(abs(x)) for a numerically stable L2 norm.
+  # 2norm(x) = a * 2norm(x/a)
+  # Scale over the full sequence, dims (1, 2)
+  alpha = tf.reduce_max(tf.abs(x), (1, 2), keep_dims=True) + 1e-12
+  l2_norm = alpha * tf.sqrt(tf.reduce_sum(tf.pow(x / alpha, 2), (1, 2),
+                                          keep_dims=True) + 1e-6)
+  x_unit = x / l2_norm
+  return norm_length * x_unit
 
 
 def _end_of_seq_mask(tokens):
@@ -225,5 +231,8 @@ def _kl_divergence_with_logits(q_logits, p_logits, weights):
   num_labels = tf.reduce_sum(weights)
   num_labels = tf.where(tf.equal(num_labels, 0.), 1., num_labels)
 
-  loss = tf.identity(tf.reduce_sum(weights * kl) / num_labels, name='kl')
+  kl.get_shape().assert_has_rank(2)
+  weights.get_shape().assert_has_rank(1)
+  loss = tf.identity(tf.reduce_sum(tf.expand_dims(weights, -1) * kl) /
+                     num_labels, name='kl')
   return loss

adversarial_text/evaluate.py

@@ -84,28 +84,35 @@ def run_eval(eval_ops, summary_writer, saver):
     metric_names, ops = zip(*eval_ops.items())
     value_ops, update_ops = zip(*ops)
 
+    value_ops_dict = dict(zip(metric_names, value_ops))
+
     # Run update ops
     num_batches = int(math.ceil(FLAGS.num_examples / FLAGS.batch_size))
     tf.logging.info('Running %d batches for evaluation.', num_batches)
     for i in range(num_batches):
       if (i + 1) % 10 == 0:
         tf.logging.info('Running batch %d/%d...', i + 1, num_batches)
+      if (i + 1) % 50 == 0:
+        _log_values(sess, value_ops_dict)
       sess.run(update_ops)
 
-    values = sess.run(value_ops)
-    metric_values = dict(zip(metric_names, values))
+    _log_values(sess, value_ops_dict, summary_writer=summary_writer)
+
 
-    tf.logging.info('Eval metric values:')
-    summary = tf.summary.Summary()
-    for name, val in metric_values.items():
-      summary.value.add(tag=name, simple_value=val)
-      tf.logging.info('%s = %.3f', name, val)
+def _log_values(sess, value_ops, summary_writer=None):
+  metric_names, value_ops = zip(*value_ops.items())
+  values = sess.run(value_ops)
 
+  tf.logging.info('Eval metric values:')
+  summary = tf.summary.Summary()
+  for name, val in zip(metric_names, values):
+    summary.value.add(tag=name, simple_value=val)
+    tf.logging.info('%s = %.3f', name, val)
+
+  if summary_writer is not None:
     global_step_val = sess.run(tf.train.get_global_step())
     summary_writer.add_summary(summary, global_step_val)
 
-    return metric_values
-
 
 def main(_):
   tf.logging.set_verbosity(tf.logging.INFO)

adversarial_text/layers.py

@@ -81,11 +81,10 @@ class Embedding(K.layers.Layer):
 
   def _normalize(self, emb):
     weights = self.vocab_freqs / tf.reduce_sum(self.vocab_freqs)
-
-    emb -= tf.reduce_sum(weights * emb, 0, keep_dims=True)
-    emb /= tf.sqrt(1e-6 + tf.reduce_sum(
-        weights * tf.pow(emb, 2.), 0, keep_dims=True))
-    return emb
+    mean = tf.reduce_sum(weights * emb, 0, keep_dims=True)
+    var = tf.reduce_sum(weights * tf.pow(emb - mean, 2.), 0, keep_dims=True)
+    stddev = tf.sqrt(1e-6 + var)
+    return (emb - mean) / stddev
 
 
 class LSTM(object):
@@ -201,7 +200,7 @@ def classification_loss(logits, labels, weights):
     logits: 2-D [timesteps*batch_size, m] float tensor, where m=1 if
       num_classes=2, otherwise m=num_classes.
     labels: 1-D [timesteps*batch_size] integer tensor.
-    weights: 2-D [timesteps*batch_size] float tensor.
+    weights: 1-D [timesteps*batch_size] float tensor.
 
   Returns:
     Loss scalar of type float.