add BERT model

* load pre-trained BERT weights from local binary
* add tests

fastNLP/models/bert.py

@@ -0,0 +1,342 @@
+import copy
+import json
+import math
+import os
+
+import torch
+from torch import nn
+
+CONFIG_FILE = 'bert_config.json'
+MODEL_WEIGHTS = 'pytorch_model.bin'
+
+
+def gelu(x):
+    return x * 0.5 * (1.0 + torch.erf(x / math.sqrt(2.0)))
+
+
+def swish(x):
+    return x * torch.sigmoid(x)
+
+
+ACT2FN = {"gelu": gelu, "relu": torch.nn.functional.relu, "swish": swish}
+
+
+class BertLayerNorm(nn.Module):
+    def __init__(self, hidden_size, eps=1e-12):
+        super(BertLayerNorm, self).__init__()
+        self.weight = nn.Parameter(torch.ones(hidden_size))
+        self.bias = nn.Parameter(torch.zeros(hidden_size))
+        self.variance_epsilon = eps
+
+    def forward(self, x):
+        u = x.mean(-1, keepdim=True)
+        s = (x - u).pow(2).mean(-1, keepdim=True)
+        x = (x - u) / torch.sqrt(s + self.variance_epsilon)
+        return self.weight * x + self.bias
+
+
+class BertEmbeddings(nn.Module):
+    def __init__(self, vocab_size, hidden_size, max_position_embeddings, type_vocab_size, hidden_dropout_prob):
+        super(BertEmbeddings, self).__init__()
+        self.word_embeddings = nn.Embedding(vocab_size, hidden_size)
+        self.position_embeddings = nn.Embedding(max_position_embeddings, hidden_size)
+        self.token_type_embeddings = nn.Embedding(type_vocab_size, hidden_size)
+
+        # self.LayerNorm is not snake-cased to stick with TensorFlow model variable name and be able to load
+        # any TensorFlow checkpoint file
+        self.LayerNorm = BertLayerNorm(hidden_size, eps=1e-12)
+        self.dropout = nn.Dropout(hidden_dropout_prob)
+
+    def forward(self, input_ids, token_type_ids=None):
+        seq_length = input_ids.size(1)
+        position_ids = torch.arange(seq_length, dtype=torch.long, device=input_ids.device)
+        position_ids = position_ids.unsqueeze(0).expand_as(input_ids)
+        if token_type_ids is None:
+            token_type_ids = torch.zeros_like(input_ids)
+
+        words_embeddings = self.word_embeddings(input_ids)
+        position_embeddings = self.position_embeddings(position_ids)
+        token_type_embeddings = self.token_type_embeddings(token_type_ids)
+
+        embeddings = words_embeddings + position_embeddings + token_type_embeddings
+        embeddings = self.LayerNorm(embeddings)
+        embeddings = self.dropout(embeddings)
+        return embeddings
+
+
+class BertSelfAttention(nn.Module):
+    def __init__(self, hidden_size, num_attention_heads, attention_probs_dropout_prob):
+        super(BertSelfAttention, self).__init__()
+        if hidden_size % num_attention_heads != 0:
+            raise ValueError(
+                "The hidden size (%d) is not a multiple of the number of attention "
+                "heads (%d)" % (hidden_size, num_attention_heads))
+        self.num_attention_heads = num_attention_heads
+        self.attention_head_size = int(hidden_size / num_attention_heads)
+        self.all_head_size = self.num_attention_heads * self.attention_head_size
+
+        self.query = nn.Linear(hidden_size, self.all_head_size)
+        self.key = nn.Linear(hidden_size, self.all_head_size)
+        self.value = nn.Linear(hidden_size, self.all_head_size)
+
+        self.dropout = nn.Dropout(attention_probs_dropout_prob)
+
+    def transpose_for_scores(self, x):
+        new_x_shape = x.size()[:-1] + (self.num_attention_heads, self.attention_head_size)
+        x = x.view(*new_x_shape)
+        return x.permute(0, 2, 1, 3)
+
+    def forward(self, hidden_states, attention_mask):
+        mixed_query_layer = self.query(hidden_states)
+        mixed_key_layer = self.key(hidden_states)
+        mixed_value_layer = self.value(hidden_states)
+
+        query_layer = self.transpose_for_scores(mixed_query_layer)
+        key_layer = self.transpose_for_scores(mixed_key_layer)
+        value_layer = self.transpose_for_scores(mixed_value_layer)
+
+        # Take the dot product between "query" and "key" to get the raw attention scores.
+        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))
+        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
+        # Apply the attention mask is (precomputed for all layers in BertModel forward() function)
+        attention_scores = attention_scores + attention_mask
+
+        # Normalize the attention scores to probabilities.
+        attention_probs = nn.Softmax(dim=-1)(attention_scores)
+
+        # This is actually dropping out entire tokens to attend to, which might
+        # seem a bit unusual, but is taken from the original Transformer paper.
+        attention_probs = self.dropout(attention_probs)
+
+        context_layer = torch.matmul(attention_probs, value_layer)
+        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
+        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
+        context_layer = context_layer.view(*new_context_layer_shape)
+        return context_layer
+
+
+class BertSelfOutput(nn.Module):
+    def __init__(self, hidden_size, hidden_dropout_prob):
+        super(BertSelfOutput, self).__init__()
+        self.dense = nn.Linear(hidden_size, hidden_size)
+        self.LayerNorm = BertLayerNorm(hidden_size, eps=1e-12)
+        self.dropout = nn.Dropout(hidden_dropout_prob)
+
+    def forward(self, hidden_states, input_tensor):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.dropout(hidden_states)
+        hidden_states = self.LayerNorm(hidden_states + input_tensor)
+        return hidden_states
+
+
+class BertAttention(nn.Module):
+    def __init__(self, hidden_size, num_attention_heads, attention_probs_dropout_prob, hidden_dropout_prob):
+        super(BertAttention, self).__init__()
+        self.self = BertSelfAttention(hidden_size, num_attention_heads, attention_probs_dropout_prob)
+        self.output = BertSelfOutput(hidden_size, hidden_dropout_prob)
+
+    def forward(self, input_tensor, attention_mask):
+        self_output = self.self(input_tensor, attention_mask)
+        attention_output = self.output(self_output, input_tensor)
+        return attention_output
+
+
+class BertIntermediate(nn.Module):
+    def __init__(self, hidden_size, intermediate_size, hidden_act):
+        super(BertIntermediate, self).__init__()
+        self.dense = nn.Linear(hidden_size, intermediate_size)
+        self.intermediate_act_fn = ACT2FN[hidden_act] \
+            if isinstance(hidden_act, str) else hidden_act
+
+    def forward(self, hidden_states):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.intermediate_act_fn(hidden_states)
+        return hidden_states
+
+
+class BertOutput(nn.Module):
+    def __init__(self, hidden_size, intermediate_size, hidden_dropout_prob):
+        super(BertOutput, self).__init__()
+        self.dense = nn.Linear(intermediate_size, hidden_size)
+        self.LayerNorm = BertLayerNorm(hidden_size, eps=1e-12)
+        self.dropout = nn.Dropout(hidden_dropout_prob)
+
+    def forward(self, hidden_states, input_tensor):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.dropout(hidden_states)
+        hidden_states = self.LayerNorm(hidden_states + input_tensor)
+        return hidden_states
+
+
+class BertLayer(nn.Module):
+    def __init__(self, hidden_size, num_attention_heads, attention_probs_dropout_prob, hidden_dropout_prob,
+                 intermediate_size, hidden_act):
+        super(BertLayer, self).__init__()
+        self.attention = BertAttention(hidden_size, num_attention_heads, attention_probs_dropout_prob,
+                                       hidden_dropout_prob)
+        self.intermediate = BertIntermediate(hidden_size, intermediate_size, hidden_act)
+        self.output = BertOutput(hidden_size, intermediate_size, hidden_dropout_prob)
+
+    def forward(self, hidden_states, attention_mask):
+        attention_output = self.attention(hidden_states, attention_mask)
+        intermediate_output = self.intermediate(attention_output)
+        layer_output = self.output(intermediate_output, attention_output)
+        return layer_output
+
+
+class BertEncoder(nn.Module):
+    def __init__(self, num_hidden_layers, hidden_size, num_attention_heads, attention_probs_dropout_prob,
+                 hidden_dropout_prob,
+                 intermediate_size, hidden_act):
+        super(BertEncoder, self).__init__()
+        layer = BertLayer(hidden_size, num_attention_heads, attention_probs_dropout_prob, hidden_dropout_prob,
+                          intermediate_size, hidden_act)
+        self.layer = nn.ModuleList([copy.deepcopy(layer) for _ in range(num_hidden_layers)])
+
+    def forward(self, hidden_states, attention_mask, output_all_encoded_layers=True):
+        all_encoder_layers = []
+        for layer_module in self.layer:
+            hidden_states = layer_module(hidden_states, attention_mask)
+            if output_all_encoded_layers:
+                all_encoder_layers.append(hidden_states)
+        if not output_all_encoded_layers:
+            all_encoder_layers.append(hidden_states)
+        return all_encoder_layers
+
+
+class BertPooler(nn.Module):
+    def __init__(self, hidden_size):
+        super(BertPooler, self).__init__()
+        self.dense = nn.Linear(hidden_size, hidden_size)
+        self.activation = nn.Tanh()
+
+    def forward(self, hidden_states):
+        # We "pool" the model by simply taking the hidden state corresponding
+        # to the first token.
+        first_token_tensor = hidden_states[:, 0]
+        pooled_output = self.dense(first_token_tensor)
+        pooled_output = self.activation(pooled_output)
+        return pooled_output
+
+
+class BertModel(nn.Module):
+    """BERT model ("Bidirectional Embedding Representations from a Transformer").
+
+    """
+
+    def __init__(self, vocab_size,
+                 hidden_size=768,
+                 num_hidden_layers=12,
+                 num_attention_heads=12,
+                 intermediate_size=3072,
+                 hidden_act="gelu",
+                 hidden_dropout_prob=0.1,
+                 attention_probs_dropout_prob=0.1,
+                 max_position_embeddings=512,
+                 type_vocab_size=2,
+                 initializer_range=0.02, **kwargs):
+        super(BertModel, self).__init__()
+        self.embeddings = BertEmbeddings(vocab_size, hidden_size, max_position_embeddings,
+                                         type_vocab_size, hidden_dropout_prob)
+        self.encoder = BertEncoder(num_hidden_layers, hidden_size, num_attention_heads,
+                                   attention_probs_dropout_prob, hidden_dropout_prob, intermediate_size,
+                                   hidden_act)
+        self.pooler = BertPooler(hidden_size)
+        self.initializer_range = initializer_range
+
+        self.apply(self.init_bert_weights)
+
+    def init_bert_weights(self, module):
+        if isinstance(module, (nn.Linear, nn.Embedding)):
+            # Slightly different from the TF version which uses truncated_normal for initialization
+            # cf https://github.com/pytorch/pytorch/pull/5617
+            module.weight.data.normal_(mean=0.0, std=self.initializer_range)
+        elif isinstance(module, BertLayerNorm):
+            module.bias.data.zero_()
+            module.weight.data.fill_(1.0)
+        if isinstance(module, nn.Linear) and module.bias is not None:
+            module.bias.data.zero_()
+
+    def forward(self, input_ids, token_type_ids=None, attention_mask=None, output_all_encoded_layers=True):
+        if attention_mask is None:
+            attention_mask = torch.ones_like(input_ids)
+        if token_type_ids is None:
+            token_type_ids = torch.zeros_like(input_ids)
+
+        # We create a 3D attention mask from a 2D tensor mask.
+        # Sizes are [batch_size, 1, 1, to_seq_length]
+        # So we can broadcast to [batch_size, num_heads, from_seq_length, to_seq_length]
+        # this attention mask is more simple than the triangular masking of causal attention
+        # used in OpenAI GPT, we just need to prepare the broadcast dimension here.
+        extended_attention_mask = attention_mask.unsqueeze(1).unsqueeze(2)
+
+        # Since attention_mask is 1.0 for positions we want to attend and 0.0 for
+        # masked positions, this operation will create a tensor which is 0.0 for
+        # positions we want to attend and -10000.0 for masked positions.
+        # Since we are adding it to the raw scores before the softmax, this is
+        # effectively the same as removing these entirely.
+        extended_attention_mask = extended_attention_mask.to(dtype=next(self.parameters()).dtype)  # fp16 compatibility
+        extended_attention_mask = (1.0 - extended_attention_mask) * -10000.0
+
+        embedding_output = self.embeddings(input_ids, token_type_ids)
+        encoded_layers = self.encoder(embedding_output,
+                                      extended_attention_mask,
+                                      output_all_encoded_layers=output_all_encoded_layers)
+        sequence_output = encoded_layers[-1]
+        pooled_output = self.pooler(sequence_output)
+        if not output_all_encoded_layers:
+            encoded_layers = encoded_layers[-1]
+        return encoded_layers, pooled_output
+
+    @classmethod
+    def from_pretrained(cls, pretrained_model_dir, state_dict=None, *inputs, **kwargs):
+        # Load config
+        config_file = os.path.join(pretrained_model_dir, CONFIG_FILE)
+        config = json.load(open(config_file, "r"))
+        # config = BertConfig.from_json_file(config_file)
+        # logger.info("Model config {}".format(config))
+        # Instantiate model.
+        model = cls(*inputs, **config, **kwargs)
+        if state_dict is None:
+            weights_path = os.path.join(pretrained_model_dir, MODEL_WEIGHTS)
+            state_dict = torch.load(weights_path)
+
+        old_keys = []
+        new_keys = []
+        for key in state_dict.keys():
+            new_key = None
+            if 'gamma' in key:
+                new_key = key.replace('gamma', 'weight')
+            if 'beta' in key:
+                new_key = key.replace('beta', 'bias')
+            if new_key:
+                old_keys.append(key)
+                new_keys.append(new_key)
+        for old_key, new_key in zip(old_keys, new_keys):
+            state_dict[new_key] = state_dict.pop(old_key)
+
+        missing_keys = []
+        unexpected_keys = []
+        error_msgs = []
+        # copy state_dict so _load_from_state_dict can modify it
+        metadata = getattr(state_dict, '_metadata', None)
+        state_dict = state_dict.copy()
+        if metadata is not None:
+            state_dict._metadata = metadata
+
+        def load(module, prefix=''):
+            local_metadata = {} if metadata is None else metadata.get(prefix[:-1], {})
+            module._load_from_state_dict(
+                state_dict, prefix, local_metadata, True, missing_keys, unexpected_keys, error_msgs)
+            for name, child in module._modules.items():
+                if child is not None:
+                    load(child, prefix + name + '.')
+
+        load(model, prefix='' if hasattr(model, 'bert') else 'bert.')
+        if len(missing_keys) > 0:
+            print("Weights of {} not initialized from pretrained model: {}".format(
+                model.__class__.__name__, missing_keys))
+        if len(unexpected_keys) > 0:
+            print("Weights from pretrained model not used in {}: {}".format(
+                model.__class__.__name__, unexpected_keys))
+        return model

fastNLP/modules/aggregator/attention.py

@@ -4,8 +4,8 @@ import torch
 import torch.nn.functional as F
 from torch import nn
 
-from fastNLP.modules.utils import mask_softmax
 from fastNLP.modules.dropout import TimestepDropout
+from fastNLP.modules.utils import mask_softmax
 
 
 class Attention(torch.nn.Module):
@@ -49,27 +49,27 @@ class DotAtte(nn.Module):
 
 
 class MultiHeadAtte(nn.Module):
-    def __init__(self, model_size, key_size, value_size, num_head, dropout=0.1):
+    def __init__(self, input_size, key_size, value_size, num_head, dropout=0.1):
         """
 
-        :param model_size: int, 输入维度的大小。同时也是输出维度的大小。
+        :param input_size: int, 输入维度的大小。同时也是输出维度的大小。
         :param key_size: int, 每个head的维度大小。
         :param value_size: int，每个head中value的维度。
         :param num_head: int，head的数量。
         :param dropout: float。
         """
         super(MultiHeadAtte, self).__init__()
-        self.input_size = model_size
+        self.input_size = input_size
         self.key_size = key_size
         self.value_size = value_size
         self.num_head = num_head
 
         in_size = key_size * num_head
-        self.q_in = nn.Linear(model_size, in_size)
-        self.k_in = nn.Linear(model_size, in_size)
-        self.v_in = nn.Linear(model_size, in_size)
+        self.q_in = nn.Linear(input_size, in_size)
+        self.k_in = nn.Linear(input_size, in_size)
+        self.v_in = nn.Linear(input_size, in_size)
         self.attention = DotAtte(key_size=key_size, value_size=value_size)
-        self.out = nn.Linear(value_size * num_head, model_size)
+        self.out = nn.Linear(value_size * num_head, input_size)
         self.drop = TimestepDropout(dropout)
         self.reset_parameters()
 
@@ -108,6 +108,7 @@ class MultiHeadAtte(nn.Module):
         output = self.drop(self.out(atte))
         return output
 
+
 class Bi_Attention(nn.Module):
     def __init__(self):
         super(Bi_Attention, self).__init__()

fastNLP/modules/encoder/transformer.py

@@ -1,4 +1,3 @@
-import torch
 from torch import nn
 
 from ..aggregator.attention import MultiHeadAtte

test/models/test_bert.py

@@ -0,0 +1,21 @@
+import unittest
+
+import torch
+
+from fastNLP.models.bert import BertModel
+
+
+class TestBert(unittest.TestCase):
+    def test_bert_1(self):
+        # model = BertModel.from_pretrained("/home/zyfeng/data/bert-base-chinese")
+        model = BertModel(vocab_size=32000, hidden_size=768,
+                          num_hidden_layers=12, num_attention_heads=12, intermediate_size=3072)
+
+        input_ids = torch.LongTensor([[31, 51, 99], [15, 5, 0]])
+        input_mask = torch.LongTensor([[1, 1, 1], [1, 1, 0]])
+        token_type_ids = torch.LongTensor([[0, 0, 1], [0, 1, 0]])
+
+        all_encoder_layers, pooled_output = model(input_ids, token_type_ids, input_mask)
+        for layer in all_encoder_layers:
+            self.assertEqual(tuple(layer.shape), (2, 3, 768))
+        self.assertEqual(tuple(pooled_output.shape), (2, 768))