Merge pull request #701 from guoshengCS/add-transformer-initializer

Add initializer for Transformer.

fluid/neural_machine_translation/transformer/model.py

 from functools import partial
 import numpy as np
 
-import paddle.v2 as paddle
 import paddle.fluid as fluid
 import paddle.fluid.layers as layers
 
@@ -31,7 +30,7 @@ def multi_head_attention(queries,
                          d_key,
                          d_value,
                          d_model,
-                         num_heads=1,
+                         n_head=1,
                          dropout_rate=0.):
     """
     Multi-Head Attention. Note that attn_bias is added to the logit before
@@ -42,41 +41,53 @@ def multi_head_attention(queries,
         raise ValueError(
             "Inputs: quries, keys and values should all be 3-D tensors.")
 
-    def __compute_qkv(queries, keys, values, num_heads, d_key, d_value):
+    def __compute_qkv(queries, keys, values, n_head, d_key, d_value):
         """
         Add linear projection to queries, keys, and values.
         """
         q = layers.fc(input=queries,
-                      size=d_key * num_heads,
+                      size=d_key * n_head,
+                      param_attr=fluid.initializer.Xavier(
+                          uniform=False,
+                          fan_in=d_model * d_key,
+                          fan_out=n_head * d_key),
                       bias_attr=False,
                       num_flatten_dims=2)
         k = layers.fc(input=keys,
-                      size=d_key * num_heads,
+                      size=d_key * n_head,
+                      param_attr=fluid.initializer.Xavier(
+                          uniform=False,
+                          fan_in=d_model * d_key,
+                          fan_out=n_head * d_key),
                       bias_attr=False,
                       num_flatten_dims=2)
         v = layers.fc(input=values,
-                      size=d_value * num_heads,
+                      size=d_value * n_head,
+                      param_attr=fluid.initializer.Xavier(
+                          uniform=False,
+                          fan_in=d_model * d_value,
+                          fan_out=n_head * d_value),
                       bias_attr=False,
                       num_flatten_dims=2)
         return q, k, v
 
-    def __split_heads(x, num_heads):
+    def __split_heads(x, n_head):
         """
         Reshape the last dimension of inpunt tensor x so that it becomes two
         dimensions and then transpose. Specifically, input a tensor with shape
-        [bs, max_sequence_length, num_heads * hidden_dim] then output a tensor
-        with shape [bs, num_heads, max_sequence_length, hidden_dim].
+        [bs, max_sequence_length, n_head * hidden_dim] then output a tensor
+        with shape [bs, n_head, max_sequence_length, hidden_dim].
         """
-        if num_heads == 1:
+        if n_head == 1:
             return x
 
         hidden_size = x.shape[-1]
         # FIXME(guosheng): Decouple the program desc with batch_size.
         reshaped = layers.reshape(
-            x=x, shape=[batch_size, -1, num_heads, hidden_size // num_heads])
+            x=x, shape=[batch_size, -1, n_head, hidden_size // n_head])
 
         # permuate the dimensions into:
-        # [batch_size, num_heads, max_sequence_len, hidden_size_per_head]
+        # [batch_size, n_head, max_sequence_len, hidden_size_per_head]
         return layers.transpose(x=reshaped, perm=[0, 2, 1, 3])
 
     def __combine_heads(x):
@@ -95,7 +106,7 @@ def multi_head_attention(queries,
             shape=map(int,
                       [batch_size, -1, trans_x.shape[2] * trans_x.shape[3]]))
 
-    def scaled_dot_product_attention(q, k, v, attn_bias, d_key, dropout_rate):
+    def scaled_dot_product_attention(q, k, v, attn_bias, d_model, dropout_rate):
         """
         Scaled Dot-Product Attention
         """
@@ -114,7 +125,7 @@ def multi_head_attention(queries,
             sum_out = layers.reduce_sum(exp_out, dim=-1, keep_dim=False)
             return layers.elementwise_div(x=exp_out, y=sum_out, axis=0)
 
-        scaled_q = layers.scale(x=q, scale=d_key**-0.5)
+        scaled_q = layers.scale(x=q, scale=d_model**-0.5)
         product = layers.matmul(x=scaled_q, y=k, transpose_y=True)
         weights = __softmax(layers.elementwise_add(x=product, y=attn_bias))
         if dropout_rate:
@@ -123,13 +134,13 @@ def multi_head_attention(queries,
         out = layers.matmul(weights, v)
         return out
 
-    q, k, v = __compute_qkv(queries, keys, values, num_heads, d_key, d_value)
+    q, k, v = __compute_qkv(queries, keys, values, n_head, d_key, d_value)
 
-    q = __split_heads(q, num_heads)
-    k = __split_heads(k, num_heads)
-    v = __split_heads(v, num_heads)
+    q = __split_heads(q, n_head)
+    k = __split_heads(k, n_head)
+    v = __split_heads(v, n_head)
 
-    ctx_multiheads = scaled_dot_product_attention(q, k, v, attn_bias, d_key,
+    ctx_multiheads = scaled_dot_product_attention(q, k, v, attn_bias, d_model,
                                                   dropout_rate)
 
     out = __combine_heads(ctx_multiheads)
@@ -137,6 +148,7 @@ def multi_head_attention(queries,
     # Project back to the model size.
     proj_out = layers.fc(input=out,
                          size=d_model,
+                         param_attr=fluid.initializer.Xavier(uniform=False),
                          bias_attr=False,
                          num_flatten_dims=2)
     return proj_out
@@ -151,8 +163,14 @@ def positionwise_feed_forward(x, d_inner_hid, d_hid):
     hidden = layers.fc(input=x,
                        size=d_inner_hid,
                        num_flatten_dims=2,
+                       param_attr=fluid.initializer.Uniform(
+                           low=-(d_hid**-0.5), high=(d_hid**-0.5)),
                        act="relu")
-    out = layers.fc(input=hidden, size=d_hid, num_flatten_dims=2)
+    out = layers.fc(input=hidden,
+                    size=d_hid,
+                    num_flatten_dims=2,
+                    param_attr=fluid.initializer.Uniform(
+                        low=-(d_inner_hid**-0.5), high=(d_inner_hid**-0.5)))
     return out
 
 
@@ -168,7 +186,11 @@ def pre_post_process_layer(prev_out, out, process_cmd, dropout=0.):
         if cmd == "a":  # add residual connection
             out = out + prev_out if prev_out else out
         elif cmd == "n":  # add layer normalization
-            out = layers.layer_norm(out, begin_norm_axis=len(out.shape) - 1)
+            out = layers.layer_norm(
+                out,
+                begin_norm_axis=len(out.shape) - 1,
+                param_attr=fluid.initializer.Constant(1.),
+                bias_attr=fluid.initializer.Constant(0.))
         elif cmd == "d":  # add dropout
             if dropout:
                 out = layers.dropout(out, dropout_prob=dropout, is_test=False)
@@ -195,7 +217,10 @@ def prepare_encoder(src_word,
     This module is used at the bottom of the encoder stacks.
     """
     src_word_emb = layers.embedding(
-        src_word, size=[src_vocab_size, src_emb_dim], padding_idx=src_pad_idx)
+        src_word,
+        size=[src_vocab_size, src_emb_dim],
+        padding_idx=src_pad_idx,
+        param_attr=fluid.initializer.Normal(0., 1.))
     src_pos_enc = layers.embedding(
         src_pos,
         size=[src_max_len, src_emb_dim],
@@ -462,6 +487,7 @@ def transformer(
     predict = layers.reshape(
         x=layers.fc(input=dec_output,
                     size=trg_vocab_size,
+                    param_attr=fluid.initializer.Xavier(uniform=False),
                     bias_attr=False,
                     num_flatten_dims=2),
         shape=[-1, trg_vocab_size],

fluid/neural_machine_translation/transformer/train.py

@@ -115,7 +115,7 @@ def main():
         paddle.reader.shuffle(
             paddle.dataset.wmt16.train(ModelHyperParams.src_vocab_size,
                                        ModelHyperParams.trg_vocab_size),
-            buf_size=51200),
+            buf_size=100000),
         batch_size=TrainTaskConfig.batch_size)
 
     # Initialize the parameters.
@@ -143,7 +143,7 @@ def main():
                            fetch_list=[cost])
             cost_val = np.array(outs[0])
             print("pass_id = " + str(pass_id) + " batch = " + str(batch_id) +
-                  " avg_cost = " + str(cost_val))
+                  " cost = " + str(cost_val))
 
 
 if __name__ == "__main__":