Merge pull request #9005 from xinliupitt:master

PiperOrigin-RevId: 324102453

official/nlp/modeling/layers/attention.py

@@ -521,11 +521,11 @@ class CachedAttention(MultiHeadAttention):
     if cache:
       key, value = self._update_cache(key, value, cache, decode_loop_step)
 
+    query = tf.multiply(query, 1.0 / math.sqrt(float(self._key_size)))
+
     # Take the dot product between "query" and "key" to get the raw
     # attention scores.
     attention_scores = tf.einsum(self._dot_product_equation, key, query)
-    attention_scores = tf.multiply(attention_scores,
-                                   1.0 / math.sqrt(float(self._key_size)))
 
     # Normalize the attention scores to probabilities.
     # `attention_scores` = [B, N, F, T]

official/nlp/modeling/layers/transformer.py

@@ -49,6 +49,12 @@ class Transformer(tf.keras.layers.Layer):
     activity_regularizer: Regularizer for dense layer activity.
     kernel_constraint: Constraint for dense layer kernels.
     bias_constraint: Constraint for dense layer kernels.
+    use_bias: Whether to enable use_bias in attention layer. If set False,
+      use_bias in attention layer is disabled.
+    norm_first: Whether to normalize inputs to attention and intermediate dense
+      layers. If set False, output of attention and intermediate dense layers is
+      normalized.
+    norm_epsilon: Epsilon value to initialize normalization layers.
   """
 
   def __init__(self,
@@ -65,6 +71,9 @@ class Transformer(tf.keras.layers.Layer):
                activity_regularizer=None,
                kernel_constraint=None,
                bias_constraint=None,
+               use_bias=True,
+               norm_first=False,
+               norm_epsilon=1e-12,
                **kwargs):
     super(Transformer, self).__init__(**kwargs)
 
@@ -81,6 +90,9 @@ class Transformer(tf.keras.layers.Layer):
     self._activity_regularizer = tf.keras.regularizers.get(activity_regularizer)
     self._kernel_constraint = tf.keras.constraints.get(kernel_constraint)
     self._bias_constraint = tf.keras.constraints.get(bias_constraint)
+    self._use_bias = use_bias
+    self._norm_first = norm_first
+    self._norm_epsilon = norm_epsilon
 
   def build(self, input_shape):
     input_tensor = input_shape[0] if len(input_shape) == 2 else input_shape
@@ -117,6 +129,7 @@ class Transformer(tf.keras.layers.Layer):
         num_heads=self._num_heads,
         key_size=self._attention_head_size,
         dropout=self._attention_dropout_rate,
+        use_bias=self._use_bias,
         name="self_attention",
         **common_kwargs)
     self._attention_dropout = tf.keras.layers.Dropout(rate=self._dropout_rate)
@@ -126,7 +139,7 @@ class Transformer(tf.keras.layers.Layer):
         tf.keras.layers.LayerNormalization(
             name="self_attention_layer_norm",
             axis=-1,
-            epsilon=1e-12,
+            epsilon=self._norm_epsilon,
             dtype=tf.float32))
     self._intermediate_dense = tf.keras.layers.experimental.EinsumDense(
         "abc,cd->abd",
@@ -151,7 +164,10 @@ class Transformer(tf.keras.layers.Layer):
     self._output_dropout = tf.keras.layers.Dropout(rate=self._dropout_rate)
     # Use float32 in layernorm for numeric stability.
     self._output_layer_norm = tf.keras.layers.LayerNormalization(
-        name="output_layer_norm", axis=-1, epsilon=1e-12, dtype=tf.float32)
+        name="output_layer_norm",
+        axis=-1,
+        epsilon=self._norm_epsilon,
+        dtype=tf.float32)
 
     super(Transformer, self).build(input_shape)
 
@@ -182,7 +198,13 @@ class Transformer(tf.keras.layers.Layer):
         "kernel_constraint":
             tf.keras.constraints.serialize(self._kernel_constraint),
         "bias_constraint":
-            tf.keras.constraints.serialize(self._bias_constraint)
+            tf.keras.constraints.serialize(self._bias_constraint),
+        "use_bias":
+            self._use_bias,
+        "norm_first":
+            self._norm_first,
+        "norm_epsilon":
+            self._norm_epsilon
     }
     base_config = super(Transformer, self).get_config()
     return dict(list(base_config.items()) + list(config.items()))
@@ -197,13 +219,22 @@ class Transformer(tf.keras.layers.Layer):
       target_tensor = input_tensor[:, 0:self._output_range, :]
       attention_mask = attention_mask[:, 0:self._output_range, :]
     else:
+      if self._norm_first:
+        source_tensor = input_tensor
+        input_tensor = self._attention_layer_norm(input_tensor)
       target_tensor = input_tensor
 
     attention_output = self._attention_layer(
         query=target_tensor, value=input_tensor, attention_mask=attention_mask)
     attention_output = self._attention_dropout(attention_output)
+    if self._norm_first:
+      attention_output = source_tensor + attention_output
+    else:
       attention_output = self._attention_layer_norm(target_tensor +
                                                     attention_output)
+    if self._norm_first:
+      source_attention_output = attention_output
+      attention_output = self._output_layer_norm(attention_output)
     intermediate_output = self._intermediate_dense(attention_output)
     intermediate_output = self._intermediate_activation_layer(
         intermediate_output)
@@ -213,6 +244,9 @@ class Transformer(tf.keras.layers.Layer):
     # is always fp32 for now. Cast layer_output to fp32 for the subsequent
     # add.
     layer_output = tf.cast(layer_output, tf.float32)
+    if self._norm_first:
+      layer_output = source_attention_output + layer_output
+    else:
       layer_output = self._output_layer_norm(layer_output + attention_output)
 
     return layer_output
@@ -251,6 +285,12 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
     activity_regularizer: Regularizer for dense layer activity.
     kernel_constraint: Constraint for dense layer kernels.
     bias_constraint: Constraint for dense layer kernels.
+    use_bias: Whether to enable use_bias in attention layer. If set False,
+      use_bias in attention layer is disabled.
+    norm_first: Whether to normalize inputs to attention and intermediate dense
+      layers. If set False, output of attention and intermediate dense layers is
+      normalized.
+    norm_epsilon: Epsilon value to initialize normalization layers.
   """
 
   def __init__(self,
@@ -267,6 +307,9 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
                activity_regularizer=None,
                kernel_constraint=None,
                bias_constraint=None,
+               use_bias=True,
+               norm_first=False,
+               norm_epsilon=1e-12,
                **kwargs):
     super(TransformerDecoderLayer, self).__init__(**kwargs)
     self.num_attention_heads = num_attention_heads
@@ -283,6 +326,9 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
     self._activity_regularizer = tf.keras.regularizers.get(activity_regularizer)
     self._kernel_constraint = tf.keras.constraints.get(kernel_constraint)
     self._bias_constraint = tf.keras.constraints.get(bias_constraint)
+    self._use_bias = use_bias
+    self._norm_first = norm_first
+    self._norm_epsilon = norm_epsilon
     if self.multi_channel_cross_attention:
       self._cross_attention_cls = multi_channel_attention.MultiChannelAttention
     else:
@@ -312,6 +358,7 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
         num_heads=self.num_attention_heads,
         key_size=self.attention_head_size,
         dropout=self.attention_dropout_rate,
+        use_bias=self._use_bias,
         name="self_attention",
         **common_kwargs)
     self.self_attention_output_dense = tf.keras.layers.experimental.EinsumDense(
@@ -324,13 +371,16 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
         rate=self.dropout_rate)
     self.self_attention_layer_norm = (
         tf.keras.layers.LayerNormalization(
-            name="self_attention_layer_norm", axis=-1, epsilon=1e-12))
+            name="self_attention_layer_norm",
+            axis=-1,
+            epsilon=self._norm_epsilon))
     # Encoder-decoder attention.
     self.encdec_attention = self._cross_attention_cls(
         num_heads=self.num_attention_heads,
         key_size=self.attention_head_size,
         dropout=self.attention_dropout_rate,
         output_shape=hidden_size,
+        use_bias=self._use_bias,
         name="attention/encdec",
         **common_kwargs)
 
@@ -338,7 +388,9 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
         rate=self.dropout_rate)
     self.encdec_attention_layer_norm = (
         tf.keras.layers.LayerNormalization(
-            name="attention/encdec_output_layer_norm", axis=-1, epsilon=1e-12))
+            name="attention/encdec_output_layer_norm",
+            axis=-1,
+            epsilon=self._norm_epsilon))
 
     # Feed-forward projection.
     self.intermediate_dense = tf.keras.layers.experimental.EinsumDense(
@@ -357,9 +409,47 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
         **common_kwargs)
     self.output_dropout = tf.keras.layers.Dropout(rate=self.dropout_rate)
     self.output_layer_norm = tf.keras.layers.LayerNormalization(
-        name="output_layer_norm", axis=-1, epsilon=1e-12)
+        name="output_layer_norm", axis=-1, epsilon=self._norm_epsilon)
     super(TransformerDecoderLayer, self).build(input_shape)
 
+  def get_config(self):
+    config = {
+        "num_attention_heads":
+            self.num_attention_heads,
+        "intermediate_size":
+            self.intermediate_size,
+        "intermediate_activation":
+            self.intermediate_activation,
+        "dropout_rate":
+            self.dropout_rate,
+        "attention_dropout_rate":
+            self.attention_dropout_rate,
+        "multi_channel_cross_attention":
+            self.multi_channel_cross_attention,
+        "kernel_initializer":
+            tf.keras.initializers.serialize(self._kernel_initializer),
+        "bias_initializer":
+            tf.keras.initializers.serialize(self._bias_initializer),
+        "kernel_regularizer":
+            tf.keras.regularizers.serialize(self._kernel_regularizer),
+        "bias_regularizer":
+            tf.keras.regularizers.serialize(self._bias_regularizer),
+        "activity_regularizer":
+            tf.keras.regularizers.serialize(self._activity_regularizer),
+        "kernel_constraint":
+            tf.keras.constraints.serialize(self._kernel_constraint),
+        "bias_constraint":
+            tf.keras.constraints.serialize(self._bias_constraint),
+        "use_bias":
+            self._use_bias,
+        "norm_first":
+            self._norm_first,
+        "norm_epsilon":
+            self._norm_epsilon
+    }
+    base_config = super(TransformerDecoderLayer, self).get_config()
+    return dict(list(base_config.items()) + list(config.items()))
+
   def common_layers_with_encoder(self):
     """Gets layer objects that can make a Transformer encoder block."""
     return [
@@ -378,6 +468,9 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
           "TransformerDecoderLayer must have 4 inputs, but it got: %d" %
           len(inputs))
     input_tensor, memory, attention_mask, self_attention_mask = inputs[:4]
+    source_tensor = input_tensor
+    if self._norm_first:
+      input_tensor = self.self_attention_layer_norm(input_tensor)
     self_attention_output, cache = self.self_attention(
         query=input_tensor,
         value=input_tensor,
@@ -385,8 +478,15 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
         cache=cache,
         decode_loop_step=decode_loop_step)
     self_attention_output = self.self_attention_dropout(self_attention_output)
+    if self._norm_first:
+      self_attention_output = source_tensor + self_attention_output
+    else:
       self_attention_output = self.self_attention_layer_norm(
           input_tensor + self_attention_output)
+    if self._norm_first:
+      source_self_attention_output = self_attention_output
+      self_attention_output = self.encdec_attention_layer_norm(
+          self_attention_output)
     cross_attn_inputs = dict(
         query=self_attention_output,
         value=memory,
@@ -396,13 +496,22 @@ class TransformerDecoderLayer(tf.keras.layers.Layer):
       cross_attn_inputs["context_attention_weights"] = inputs[-1]
     attention_output = self.encdec_attention(**cross_attn_inputs)
     attention_output = self.encdec_attention_dropout(attention_output)
-    attention_output = self.encdec_attention_layer_norm(self_attention_output +
-                                                        attention_output)
+    if self._norm_first:
+      attention_output = source_self_attention_output + attention_output
+    else:
+      attention_output = self.encdec_attention_layer_norm(
+          self_attention_output + attention_output)
+    if self._norm_first:
+      source_attention_output = attention_output
+      attention_output = self.output_layer_norm(attention_output)
 
     intermediate_output = self.intermediate_dense(attention_output)
     intermediate_output = self.intermediate_activation_layer(
         intermediate_output)
     layer_output = self.output_dense(intermediate_output)
     layer_output = self.output_dropout(layer_output)
+    if self._norm_first:
+      layer_output = source_attention_output + layer_output
+    else:
       layer_output = self.output_layer_norm(layer_output + attention_output)
     return layer_output, cache

official/nlp/modeling/layers/transformer_test.py

@@ -152,10 +152,8 @@ class TransformerLayerTest(keras_parameterized.TestCase):
     _ = new_layer([input_data, mask_data])
     new_layer.set_weights(test_layer.get_weights())
     new_output_tensor = new_layer([input_data, mask_data])
-    self.assertAllClose(new_output_tensor,
-                        output_tensor[:, 0:1, :],
-                        atol=5e-5,
-                        rtol=0.003)
+    self.assertAllClose(
+        new_output_tensor, output_tensor[:, 0:1, :], atol=5e-5, rtol=0.003)
 
   def test_layer_invocation_with_float16_dtype(self, transformer_cls):
     tf.keras.mixed_precision.experimental.set_policy('mixed_float16')
@@ -218,6 +216,45 @@ class TransformerLayerTest(keras_parameterized.TestCase):
     self.assertAllEqual([1, input_length, width], output_data.shape)
 
 
+@keras_parameterized.run_all_keras_modes
+class TransformerArgumentTest(keras_parameterized.TestCase):
+
+  def test_use_bias_norm_first(self):
+    num_attention_heads = 2
+    hidden_size = 16
+    encoder_block = transformer.Transformer(
+        num_attention_heads=num_attention_heads,
+        intermediate_size=32,
+        intermediate_activation='relu',
+        dropout_rate=0.1,
+        attention_dropout_rate=0.1,
+        use_bias=False,
+        norm_first=True,
+        norm_epsilon=1e-6)
+    # Forward path.
+    dummy_tensor = tf.zeros([2, 4, 16], dtype=tf.float32)
+    dummy_mask = tf.zeros([2, 4, 4], dtype=tf.float32)
+    inputs = [dummy_tensor, dummy_mask]
+    output = encoder_block(inputs)
+    self.assertEqual(output.shape, (2, 4, hidden_size))
+
+  def test_get_config(self):
+    num_attention_heads = 2
+    encoder_block = transformer.Transformer(
+        num_attention_heads=num_attention_heads,
+        intermediate_size=32,
+        intermediate_activation='relu',
+        dropout_rate=0.1,
+        attention_dropout_rate=0.1,
+        use_bias=False,
+        norm_first=True,
+        norm_epsilon=1e-6)
+    encoder_block_config = encoder_block.get_config()
+    new_encoder_block = transformer.Transformer.from_config(
+        encoder_block_config)
+    self.assertEqual(encoder_block_config, new_encoder_block.get_config())
+
+
 def _create_cache(batch_size, init_decode_length, num_heads, head_size):
   return {
       'key':
@@ -251,6 +288,41 @@ class TransformerDecoderLayerTest(keras_parameterized.TestCase):
     self.assertEqual(output.shape, (2, 4, hidden_size))
     self.assertEqual(cache['value'].shape, (2, 4, 2, 8))
 
+  def test_use_bias_norm_first(self):
+    num_attention_heads = 2
+    hidden_size = 16
+    decoder_block = transformer.TransformerDecoderLayer(
+        num_attention_heads=num_attention_heads,
+        intermediate_size=32,
+        intermediate_activation='relu',
+        dropout_rate=0.1,
+        attention_dropout_rate=0.1,
+        use_bias=False,
+        norm_first=True,
+        norm_epsilon=1e-6)
+    # Forward path.
+    dummy_tensor = tf.zeros([2, 4, 16], dtype=tf.float32)
+    dummy_mask = tf.zeros([2, 4, 4], dtype=tf.float32)
+    inputs = [dummy_tensor, dummy_tensor, dummy_mask, dummy_mask]
+    output, _ = decoder_block(inputs)
+    self.assertEqual(output.shape, (2, 4, hidden_size))
+
+  def test_get_config(self):
+    num_attention_heads = 2
+    decoder_block = transformer.TransformerDecoderLayer(
+        num_attention_heads=num_attention_heads,
+        intermediate_size=32,
+        intermediate_activation='relu',
+        dropout_rate=0.1,
+        attention_dropout_rate=0.1,
+        use_bias=False,
+        norm_first=True,
+        norm_epsilon=1e-6)
+    decoder_block_config = decoder_block.get_config()
+    new_decoder_block = transformer.TransformerDecoderLayer.from_config(
+        decoder_block_config)
+    self.assertEqual(decoder_block_config, new_decoder_block.get_config())
+
 
 if __name__ == '__main__':
   tf.test.main()