# Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. from __future__ import print_function import numpy as np import paddle.fluid as fluid import paddle.fluid.layers as layers from paddle.fluid.dygraph import Embedding, LayerNorm, Linear, Layer, to_variable from paddle.fluid.dygraph.learning_rate_scheduler import LearningRateDecay from model import Model, CrossEntropy, Loss from text import TransformerBeamSearchDecoder, DynamicDecode def position_encoding_init(n_position, d_pos_vec): """ Generate the initial values for the sinusoid position encoding table. """ channels = d_pos_vec position = np.arange(n_position) num_timescales = channels // 2 log_timescale_increment = (np.log(float(1e4) / float(1)) / (num_timescales - 1)) inv_timescales = np.exp(np.arange( num_timescales)) * -log_timescale_increment scaled_time = np.expand_dims(position, 1) * np.expand_dims(inv_timescales, 0) signal = np.concatenate([np.sin(scaled_time), np.cos(scaled_time)], axis=1) signal = np.pad(signal, [[0, 0], [0, np.mod(channels, 2)]], 'constant') position_enc = signal return position_enc.astype("float32") class NoamDecay(LearningRateDecay): """ learning rate scheduler """ def __init__(self, d_model, warmup_steps, static_lr=2.0, begin=1, step=1, dtype='float32'): super(NoamDecay, self).__init__(begin, step, dtype) self.d_model = d_model self.warmup_steps = warmup_steps self.static_lr = static_lr def step(self): a = self.create_lr_var(self.step_num**-0.5) b = self.create_lr_var((self.warmup_steps**-1.5) * self.step_num) lr_value = (self.d_model**-0.5) * layers.elementwise_min( a, b) * self.static_lr return lr_value class PrePostProcessLayer(Layer): """ PrePostProcessLayer """ def __init__(self, process_cmd, d_model, dropout_rate): super(PrePostProcessLayer, self).__init__() self.process_cmd = process_cmd self.functors = [] for cmd in self.process_cmd: if cmd == "a": # add residual connection self.functors.append(lambda x, y: x + y if y else x) elif cmd == "n": # add layer normalization self.functors.append( self.add_sublayer( "layer_norm_%d" % len( self.sublayers(include_sublayers=False)), LayerNorm( normalized_shape=d_model, param_attr=fluid.ParamAttr( initializer=fluid.initializer.Constant(1.)), bias_attr=fluid.ParamAttr( initializer=fluid.initializer.Constant(0.))))) elif cmd == "d": # add dropout self.functors.append(lambda x: layers.dropout( x, dropout_prob=dropout_rate, is_test=False) if dropout_rate else x) def forward(self, x, residual=None): for i, cmd in enumerate(self.process_cmd): if cmd == "a": x = self.functors[i](x, residual) else: x = self.functors[i](x) return x class MultiHeadAttention(Layer): """ Multi-Head Attention """ def __init__(self, d_key, d_value, d_model, n_head=1, dropout_rate=0.): super(MultiHeadAttention, self).__init__() self.n_head = n_head self.d_key = d_key self.d_value = d_value self.d_model = d_model self.dropout_rate = dropout_rate self.q_fc = Linear( input_dim=d_model, output_dim=d_key * n_head, bias_attr=False) self.k_fc = Linear( input_dim=d_model, output_dim=d_key * n_head, bias_attr=False) self.v_fc = Linear( input_dim=d_model, output_dim=d_value * n_head, bias_attr=False) self.proj_fc = Linear( input_dim=d_value * n_head, output_dim=d_model, bias_attr=False) def _prepare_qkv(self, queries, keys, values, cache=None): if keys is None: # self-attention keys, values = queries, queries static_kv = False else: # cross-attention static_kv = True q = self.q_fc(queries) q = layers.reshape(x=q, shape=[0, 0, self.n_head, self.d_key]) q = layers.transpose(x=q, perm=[0, 2, 1, 3]) if cache is not None and static_kv and "static_k" in cache: # for encoder-decoder attention in inference and has cached k = cache["static_k"] v = cache["static_v"] else: k = self.k_fc(keys) v = self.v_fc(values) k = layers.reshape(x=k, shape=[0, 0, self.n_head, self.d_key]) k = layers.transpose(x=k, perm=[0, 2, 1, 3]) v = layers.reshape(x=v, shape=[0, 0, self.n_head, self.d_value]) v = layers.transpose(x=v, perm=[0, 2, 1, 3]) if cache is not None: if static_kv and not "static_k" in cache: # for encoder-decoder attention in inference and has not cached cache["static_k"], cache["static_v"] = k, v elif not static_kv: # for decoder self-attention in inference cache_k, cache_v = cache["k"], cache["v"] k = layers.concat([cache_k, k], axis=2) v = layers.concat([cache_v, v], axis=2) cache["k"], cache["v"] = k, v return q, k, v def forward(self, queries, keys, values, attn_bias, cache=None): # compute q ,k ,v q, k, v = self._prepare_qkv(queries, keys, values, cache) # scale dot product attention product = layers.matmul( x=q, y=k, transpose_y=True, alpha=self.d_model**-0.5) if attn_bias: product += attn_bias weights = layers.softmax(product) if self.dropout_rate: weights = layers.dropout( weights, dropout_prob=self.dropout_rate, is_test=False) out = layers.matmul(weights, v) # combine heads out = layers.transpose(out, perm=[0, 2, 1, 3]) out = layers.reshape(x=out, shape=[0, 0, out.shape[2] * out.shape[3]]) # project to output out = self.proj_fc(out) return out def cal_kv(self, keys, values): k = self.k_fc(keys) v = self.v_fc(values) k = layers.reshape(x=k, shape=[0, 0, self.n_head, self.d_key]) k = layers.transpose(x=k, perm=[0, 2, 1, 3]) v = layers.reshape(x=v, shape=[0, 0, self.n_head, self.d_value]) v = layers.transpose(x=v, perm=[0, 2, 1, 3]) return k, v class FFN(Layer): """ Feed-Forward Network """ def __init__(self, d_inner_hid, d_model, dropout_rate): super(FFN, self).__init__() self.dropout_rate = dropout_rate self.fc1 = Linear( input_dim=d_model, output_dim=d_inner_hid, act="relu") self.fc2 = Linear(input_dim=d_inner_hid, output_dim=d_model) def forward(self, x): hidden = self.fc1(x) if self.dropout_rate: hidden = layers.dropout( hidden, dropout_prob=self.dropout_rate, is_test=False) out = self.fc2(hidden) return out class EncoderLayer(Layer): """ EncoderLayer """ def __init__(self, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd="n", postprocess_cmd="da"): super(EncoderLayer, self).__init__() self.preprocesser1 = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) self.self_attn = MultiHeadAttention(d_key, d_value, d_model, n_head, attention_dropout) self.postprocesser1 = PrePostProcessLayer(postprocess_cmd, d_model, prepostprocess_dropout) self.preprocesser2 = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) self.ffn = FFN(d_inner_hid, d_model, relu_dropout) self.postprocesser2 = PrePostProcessLayer(postprocess_cmd, d_model, prepostprocess_dropout) def forward(self, enc_input, attn_bias): attn_output = self.self_attn( self.preprocesser1(enc_input), None, None, attn_bias) attn_output = self.postprocesser1(attn_output, enc_input) ffn_output = self.ffn(self.preprocesser2(attn_output)) ffn_output = self.postprocesser2(ffn_output, attn_output) return ffn_output class Encoder(Layer): """ encoder """ def __init__(self, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd="n", postprocess_cmd="da"): super(Encoder, self).__init__() self.encoder_layers = list() for i in range(n_layer): self.encoder_layers.append( self.add_sublayer( "layer_%d" % i, EncoderLayer(n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd))) self.processer = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) def forward(self, enc_input, attn_bias): for encoder_layer in self.encoder_layers: enc_output = encoder_layer(enc_input, attn_bias) enc_input = enc_output return self.processer(enc_output) class Embedder(Layer): """ Word Embedding + Position Encoding """ def __init__(self, vocab_size, emb_dim, bos_idx=0): super(Embedder, self).__init__() self.word_embedder = Embedding( size=[vocab_size, emb_dim], padding_idx=bos_idx, param_attr=fluid.ParamAttr( initializer=fluid.initializer.Normal(0., emb_dim**-0.5))) def forward(self, word): word_emb = self.word_embedder(word) return word_emb class WrapEncoder(Layer): """ embedder + encoder """ def __init__(self, src_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, word_embedder): super(WrapEncoder, self).__init__() self.emb_dropout = prepostprocess_dropout self.emb_dim = d_model self.word_embedder = word_embedder self.pos_encoder = Embedding( size=[max_length, self.emb_dim], param_attr=fluid.ParamAttr( initializer=fluid.initializer.NumpyArrayInitializer( position_encoding_init(max_length, self.emb_dim)), trainable=False)) self.encoder = Encoder(n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd) def forward(self, src_word, src_pos, src_slf_attn_bias): word_emb = self.word_embedder(src_word) word_emb = layers.scale(x=word_emb, scale=self.emb_dim**0.5) pos_enc = self.pos_encoder(src_pos) pos_enc.stop_gradient = True emb = word_emb + pos_enc enc_input = layers.dropout( emb, dropout_prob=self.emb_dropout, is_test=False) if self.emb_dropout else emb enc_output = self.encoder(enc_input, src_slf_attn_bias) return enc_output class DecoderLayer(Layer): """ decoder """ def __init__(self, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd="n", postprocess_cmd="da"): super(DecoderLayer, self).__init__() self.preprocesser1 = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) self.self_attn = MultiHeadAttention(d_key, d_value, d_model, n_head, attention_dropout) self.postprocesser1 = PrePostProcessLayer(postprocess_cmd, d_model, prepostprocess_dropout) self.preprocesser2 = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) self.cross_attn = MultiHeadAttention(d_key, d_value, d_model, n_head, attention_dropout) self.postprocesser2 = PrePostProcessLayer(postprocess_cmd, d_model, prepostprocess_dropout) self.preprocesser3 = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) self.ffn = FFN(d_inner_hid, d_model, relu_dropout) self.postprocesser3 = PrePostProcessLayer(postprocess_cmd, d_model, prepostprocess_dropout) def forward(self, dec_input, enc_output, self_attn_bias, cross_attn_bias, cache=None): self_attn_output = self.self_attn( self.preprocesser1(dec_input), None, None, self_attn_bias, cache) self_attn_output = self.postprocesser1(self_attn_output, dec_input) cross_attn_output = self.cross_attn( self.preprocesser2(self_attn_output), enc_output, enc_output, cross_attn_bias, cache) cross_attn_output = self.postprocesser2(cross_attn_output, self_attn_output) ffn_output = self.ffn(self.preprocesser3(cross_attn_output)) ffn_output = self.postprocesser3(ffn_output, cross_attn_output) return ffn_output class Decoder(Layer): """ decoder """ def __init__(self, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd): super(Decoder, self).__init__() self.decoder_layers = list() for i in range(n_layer): self.decoder_layers.append( self.add_sublayer( "layer_%d" % i, DecoderLayer(n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd))) self.processer = PrePostProcessLayer(preprocess_cmd, d_model, prepostprocess_dropout) def forward(self, dec_input, enc_output, self_attn_bias, cross_attn_bias, caches=None): for i, decoder_layer in enumerate(self.decoder_layers): dec_output = decoder_layer(dec_input, enc_output, self_attn_bias, cross_attn_bias, None if caches is None else caches[i]) dec_input = dec_output return self.processer(dec_output) def prepare_static_cache(self, enc_output): return [ dict( zip(("static_k", "static_v"), decoder_layer.cross_attn.cal_kv(enc_output, enc_output))) for decoder_layer in self.decoder_layers ] class WrapDecoder(Layer): """ embedder + decoder """ def __init__(self, trg_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, share_input_output_embed, word_embedder): super(WrapDecoder, self).__init__() self.emb_dropout = prepostprocess_dropout self.emb_dim = d_model self.word_embedder = word_embedder self.pos_encoder = Embedding( size=[max_length, self.emb_dim], param_attr=fluid.ParamAttr( initializer=fluid.initializer.NumpyArrayInitializer( position_encoding_init(max_length, self.emb_dim)), trainable=False)) self.decoder = Decoder(n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd) if share_input_output_embed: self.linear = lambda x: layers.matmul(x=x, y=self.word_embedder. word_embedder.weight, transpose_y=True) else: self.linear = Linear( input_dim=d_model, output_dim=trg_vocab_size, bias_attr=False) def forward(self, trg_word, trg_pos, trg_slf_attn_bias, trg_src_attn_bias, enc_output, caches=None): word_emb = self.word_embedder(trg_word) word_emb = layers.scale(x=word_emb, scale=self.emb_dim**0.5) pos_enc = self.pos_encoder(trg_pos) pos_enc.stop_gradient = True emb = word_emb + pos_enc dec_input = layers.dropout( emb, dropout_prob=self.emb_dropout, is_test=False) if self.emb_dropout else emb dec_output = self.decoder(dec_input, enc_output, trg_slf_attn_bias, trg_src_attn_bias, caches) dec_output = layers.reshape( dec_output, shape=[-1, dec_output.shape[-1]], ) logits = self.linear(dec_output) return logits class CrossEntropyCriterion(Loss): def __init__(self, label_smooth_eps): super(CrossEntropyCriterion, self).__init__() self.label_smooth_eps = label_smooth_eps def forward(self, outputs, labels): predict, (label, weights) = outputs[0], labels if self.label_smooth_eps: label = layers.label_smooth( label=layers.one_hot( input=label, depth=predict.shape[-1]), epsilon=self.label_smooth_eps) cost = layers.softmax_with_cross_entropy( logits=predict, label=label, soft_label=True if self.label_smooth_eps else False) weighted_cost = cost * weights sum_cost = layers.reduce_sum(weighted_cost) token_num = layers.reduce_sum(weights) token_num.stop_gradient = True avg_cost = sum_cost / token_num return avg_cost class Transformer(Model): """ model """ def __init__(self, src_vocab_size, trg_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, weight_sharing, bos_id=0, eos_id=1): super(Transformer, self).__init__() src_word_embedder = Embedder( vocab_size=src_vocab_size, emb_dim=d_model, bos_idx=bos_id) self.encoder = WrapEncoder( src_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, src_word_embedder) if weight_sharing: assert src_vocab_size == trg_vocab_size, ( "Vocabularies in source and target should be same for weight sharing." ) trg_word_embedder = src_word_embedder else: trg_word_embedder = Embedder( vocab_size=trg_vocab_size, emb_dim=d_model, bos_idx=bos_id) self.decoder = WrapDecoder( trg_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, weight_sharing, trg_word_embedder) self.trg_vocab_size = trg_vocab_size self.n_layer = n_layer self.n_head = n_head self.d_key = d_key self.d_value = d_value def forward(self, src_word, src_pos, src_slf_attn_bias, trg_word, trg_pos, trg_slf_attn_bias, trg_src_attn_bias): enc_output = self.encoder(src_word, src_pos, src_slf_attn_bias) predict = self.decoder(trg_word, trg_pos, trg_slf_attn_bias, trg_src_attn_bias, enc_output) return predict class TransfomerCell(object): """ Let inputs=(trg_word, trg_pos), states=cache to make Transformer can be used as RNNCell """ def __init__(self, decoder): self.decoder = decoder def __call__(self, inputs, states, trg_src_attn_bias, enc_output, static_caches): trg_word, trg_pos = inputs for cache, static_cache in zip(states, static_caches): cache.update(static_cache) logits = self.decoder(trg_word, trg_pos, None, trg_src_attn_bias, enc_output, states) new_states = [{"k": cache["k"], "v": cache["v"]} for cache in states] return logits, new_states class InferTransformer(Transformer): """ model for prediction """ def __init__(self, src_vocab_size, trg_vocab_size, max_length, n_layer, n_head, d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout, attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd, weight_sharing, bos_id=0, eos_id=1, beam_size=4, max_out_len=256): args = dict(locals()) args.pop("self") args.pop("__class__", None) # py3 self.beam_size = args.pop("beam_size") self.max_out_len = args.pop("max_out_len") super(InferTransformer, self).__init__(**args) cell = TransfomerCell(self.decoder) self.beam_search_decoder = DynamicDecode( TransformerBeamSearchDecoder( cell, bos_id, eos_id, beam_size, var_dim_in_state=2), max_out_len, is_test=True) def forward(self, src_word, src_pos, src_slf_attn_bias, trg_src_attn_bias): enc_output = self.encoder(src_word, src_pos, src_slf_attn_bias) ## init states (caches) for transformer, need to be updated according to selected beam caches = [{ "k": layers.fill_constant_batch_size_like( input=enc_output, shape=[-1, self.n_head, 0, self.d_key], dtype=enc_output.dtype, value=0), "v": layers.fill_constant_batch_size_like( input=enc_output, shape=[-1, self.n_head, 0, self.d_value], dtype=enc_output.dtype, value=0), } for i in range(self.n_layer)] enc_output = TransformerBeamSearchDecoder.tile_beam_merge_with_batch( enc_output, self.beam_size) trg_src_attn_bias = TransformerBeamSearchDecoder.tile_beam_merge_with_batch( trg_src_attn_bias, self.beam_size) static_caches = self.decoder.decoder.prepare_static_cache(enc_output) rs, _ = self.beam_search_decoder( inits=caches, enc_output=enc_output, trg_src_attn_bias=trg_src_attn_bias, static_caches=static_caches) return rs