# copyright (c) 2021 PaddlePaddle Authors. All Rights Reserve. # # 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. import math import paddle import copy from paddle import nn import paddle.nn.functional as F from paddle.nn import LayerList from paddle.nn.initializer import XavierNormal as xavier_uniform_ from paddle.nn import Dropout, Linear, LayerNorm, Conv2D import numpy as np from ppocr.modeling.heads.multiheadAttention import MultiheadAttention from paddle.nn.initializer import Constant as constant_ from paddle.nn.initializer import XavierNormal as xavier_normal_ zeros_ = constant_(value=0.) ones_ = constant_(value=1.) class Transformer(nn.Layer): """A transformer model. User is able to modify the attributes as needed. The architechture is based on the paper "Attention Is All You Need". Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez, Lukasz Kaiser, and Illia Polosukhin. 2017. Attention is all you need. In Advances in Neural Information Processing Systems, pages 6000-6010. Args: d_model: the number of expected features in the encoder/decoder inputs (default=512). nhead: the number of heads in the multiheadattention models (default=8). num_encoder_layers: the number of sub-encoder-layers in the encoder (default=6). num_decoder_layers: the number of sub-decoder-layers in the decoder (default=6). dim_feedforward: the dimension of the feedforward network model (default=2048). dropout: the dropout value (default=0.1). custom_encoder: custom encoder (default=None). custom_decoder: custom decoder (default=None). """ def __init__(self, d_model=512, nhead=8, num_encoder_layers=6, beam_size=0, num_decoder_layers=6, dim_feedforward=1024, attention_dropout_rate=0.0, residual_dropout_rate=0.1, custom_encoder=None, custom_decoder=None, in_channels=0, out_channels=0, scale_embedding=True): super(Transformer, self).__init__() self.out_channels = out_channels + 1 self.embedding = Embeddings( d_model=d_model, vocab=self.out_channels, padding_idx=0, scale_embedding=scale_embedding) self.positional_encoding = PositionalEncoding( dropout=residual_dropout_rate, dim=d_model, ) if custom_encoder is not None: self.encoder = custom_encoder else: if num_encoder_layers > 0: encoder_layer = TransformerEncoderLayer( d_model, nhead, dim_feedforward, attention_dropout_rate, residual_dropout_rate) self.encoder = TransformerEncoder(encoder_layer, num_encoder_layers) else: self.encoder = None if custom_decoder is not None: self.decoder = custom_decoder else: decoder_layer = TransformerDecoderLayer( d_model, nhead, dim_feedforward, attention_dropout_rate, residual_dropout_rate) self.decoder = TransformerDecoder(decoder_layer, num_decoder_layers) self._reset_parameters() self.beam_size = beam_size self.d_model = d_model self.nhead = nhead self.tgt_word_prj = nn.Linear( d_model, self.out_channels, bias_attr=False) w0 = np.random.normal(0.0, d_model**-0.5, (d_model, self.out_channels)).astype(np.float32) self.tgt_word_prj.weight.set_value(w0) self.apply(self._init_weights) def _init_weights(self, m): if isinstance(m, nn.Conv2D): xavier_normal_(m.weight) if m.bias is not None: zeros_(m.bias) def forward_train(self, src, tgt): tgt = tgt[:, :-1] tgt_key_padding_mask = self.generate_padding_mask(tgt) tgt = self.embedding(tgt).transpose([1, 0, 2]) tgt = self.positional_encoding(tgt) tgt_mask = self.generate_square_subsequent_mask(tgt.shape[0]) if self.encoder is not None: src = self.positional_encoding(src.transpose([1, 0, 2])) memory = self.encoder(src) else: memory = src.squeeze(2).transpose([2, 0, 1]) output = self.decoder( tgt, memory, tgt_mask=tgt_mask, memory_mask=None, tgt_key_padding_mask=tgt_key_padding_mask, memory_key_padding_mask=None) output = output.transpose([1, 0, 2]) logit = self.tgt_word_prj(output) return logit def forward(self, src, targets=None): """Take in and process masked source/target sequences. Args: src: the sequence to the encoder (required). tgt: the sequence to the decoder (required). Shape: - src: :math:`(S, N, E)`. - tgt: :math:`(T, N, E)`. Examples: >>> output = transformer_model(src, tgt) """ if self.training: max_len = targets[1].max() tgt = targets[0][:, :2 + max_len] return self.forward_train(src, tgt) else: if self.beam_size > 0: return self.forward_beam(src) else: return self.forward_test(src) def forward_test(self, src): bs = paddle.shape(src)[0] if self.encoder is not None: src = self.positional_encoding(paddle.transpose(src, [1, 0, 2])) memory = self.encoder(src) else: memory = paddle.transpose(paddle.squeeze(src, 2), [2, 0, 1]) dec_seq = paddle.full((bs, 1), 2, dtype=paddle.int64) dec_prob = paddle.full((bs, 1), 1., dtype=paddle.float32) for len_dec_seq in range(1, 25): dec_seq_embed = paddle.transpose(self.embedding(dec_seq), [1, 0, 2]) dec_seq_embed = self.positional_encoding(dec_seq_embed) tgt_mask = self.generate_square_subsequent_mask( paddle.shape(dec_seq_embed)[0]) output = self.decoder( dec_seq_embed, memory, tgt_mask=tgt_mask, memory_mask=None, tgt_key_padding_mask=None, memory_key_padding_mask=None) dec_output = paddle.transpose(output, [1, 0, 2]) dec_output = dec_output[:, -1, :] word_prob = F.softmax(self.tgt_word_prj(dec_output), axis=1) preds_idx = paddle.argmax(word_prob, axis=1) if paddle.equal_all( preds_idx, paddle.full( paddle.shape(preds_idx), 3, dtype='int64')): break preds_prob = paddle.max(word_prob, axis=1) dec_seq = paddle.concat( [dec_seq, paddle.reshape(preds_idx, [-1, 1])], axis=1) dec_prob = paddle.concat( [dec_prob, paddle.reshape(preds_prob, [-1, 1])], axis=1) return [dec_seq, dec_prob] def forward_beam(self, images): ''' Translation work in one batch ''' def get_inst_idx_to_tensor_position_map(inst_idx_list): ''' Indicate the position of an instance in a tensor. ''' return { inst_idx: tensor_position for tensor_position, inst_idx in enumerate(inst_idx_list) } def collect_active_part(beamed_tensor, curr_active_inst_idx, n_prev_active_inst, n_bm): ''' Collect tensor parts associated to active instances. ''' beamed_tensor_shape = paddle.shape(beamed_tensor) n_curr_active_inst = len(curr_active_inst_idx) new_shape = (n_curr_active_inst * n_bm, beamed_tensor_shape[1], beamed_tensor_shape[2]) beamed_tensor = beamed_tensor.reshape([n_prev_active_inst, -1]) beamed_tensor = beamed_tensor.index_select( curr_active_inst_idx, axis=0) beamed_tensor = beamed_tensor.reshape(new_shape) return beamed_tensor def collate_active_info(src_enc, inst_idx_to_position_map, active_inst_idx_list): # Sentences which are still active are collected, # so the decoder will not run on completed sentences. n_prev_active_inst = len(inst_idx_to_position_map) active_inst_idx = [ inst_idx_to_position_map[k] for k in active_inst_idx_list ] active_inst_idx = paddle.to_tensor(active_inst_idx, dtype='int64') active_src_enc = collect_active_part( src_enc.transpose([1, 0, 2]), active_inst_idx, n_prev_active_inst, n_bm).transpose([1, 0, 2]) active_inst_idx_to_position_map = get_inst_idx_to_tensor_position_map( active_inst_idx_list) return active_src_enc, active_inst_idx_to_position_map def beam_decode_step(inst_dec_beams, len_dec_seq, enc_output, inst_idx_to_position_map, n_bm, memory_key_padding_mask): ''' Decode and update beam status, and then return active beam idx ''' def prepare_beam_dec_seq(inst_dec_beams, len_dec_seq): dec_partial_seq = [ b.get_current_state() for b in inst_dec_beams if not b.done ] dec_partial_seq = paddle.stack(dec_partial_seq) dec_partial_seq = dec_partial_seq.reshape([-1, len_dec_seq]) return dec_partial_seq def predict_word(dec_seq, enc_output, n_active_inst, n_bm, memory_key_padding_mask): dec_seq = paddle.transpose(self.embedding(dec_seq), [1, 0, 2]) dec_seq = self.positional_encoding(dec_seq) tgt_mask = self.generate_square_subsequent_mask( paddle.shape(dec_seq)[0]) dec_output = self.decoder( dec_seq, enc_output, tgt_mask=tgt_mask, tgt_key_padding_mask=None, memory_key_padding_mask=memory_key_padding_mask, ) dec_output = paddle.transpose(dec_output, [1, 0, 2]) dec_output = dec_output[:, -1, :] # Pick the last step: (bh * bm) * d_h word_prob = F.softmax(self.tgt_word_prj(dec_output), axis=1) word_prob = paddle.reshape(word_prob, [n_active_inst, n_bm, -1]) return word_prob def collect_active_inst_idx_list(inst_beams, word_prob, inst_idx_to_position_map): active_inst_idx_list = [] for inst_idx, inst_position in inst_idx_to_position_map.items(): is_inst_complete = inst_beams[inst_idx].advance(word_prob[ inst_position]) if not is_inst_complete: active_inst_idx_list += [inst_idx] return active_inst_idx_list n_active_inst = len(inst_idx_to_position_map) dec_seq = prepare_beam_dec_seq(inst_dec_beams, len_dec_seq) word_prob = predict_word(dec_seq, enc_output, n_active_inst, n_bm, None) # Update the beam with predicted word prob information and collect incomplete instances active_inst_idx_list = collect_active_inst_idx_list( inst_dec_beams, word_prob, inst_idx_to_position_map) return active_inst_idx_list def collect_hypothesis_and_scores(inst_dec_beams, n_best): all_hyp, all_scores = [], [] for inst_idx in range(len(inst_dec_beams)): scores, tail_idxs = inst_dec_beams[inst_idx].sort_scores() all_scores += [scores[:n_best]] hyps = [ inst_dec_beams[inst_idx].get_hypothesis(i) for i in tail_idxs[:n_best] ] all_hyp += [hyps] return all_hyp, all_scores with paddle.no_grad(): #-- Encode if self.encoder is not None: src = self.positional_encoding(images.transpose([1, 0, 2])) src_enc = self.encoder(src) else: src_enc = images.squeeze(2).transpose([0, 2, 1]) n_bm = self.beam_size src_shape = paddle.shape(src_enc) inst_dec_beams = [Beam(n_bm) for _ in range(1)] active_inst_idx_list = list(range(1)) # Repeat data for beam search src_enc = paddle.tile(src_enc, [1, n_bm, 1]) inst_idx_to_position_map = get_inst_idx_to_tensor_position_map( active_inst_idx_list) # Decode for len_dec_seq in range(1, 25): src_enc_copy = src_enc.clone() active_inst_idx_list = beam_decode_step( inst_dec_beams, len_dec_seq, src_enc_copy, inst_idx_to_position_map, n_bm, None) if not active_inst_idx_list: break # all instances have finished their path to src_enc, inst_idx_to_position_map = collate_active_info( src_enc_copy, inst_idx_to_position_map, active_inst_idx_list) batch_hyp, batch_scores = collect_hypothesis_and_scores(inst_dec_beams, 1) result_hyp = [] hyp_scores = [] for bs_hyp, score in zip(batch_hyp, batch_scores): l = len(bs_hyp[0]) bs_hyp_pad = bs_hyp[0] + [3] * (25 - l) result_hyp.append(bs_hyp_pad) score = float(score) / l hyp_score = [score for _ in range(25)] hyp_scores.append(hyp_score) return [ paddle.to_tensor( np.array(result_hyp), dtype=paddle.int64), paddle.to_tensor(hyp_scores) ] def generate_square_subsequent_mask(self, sz): """Generate a square mask for the sequence. The masked positions are filled with float('-inf'). Unmasked positions are filled with float(0.0). """ mask = paddle.zeros([sz, sz], dtype='float32') mask_inf = paddle.triu( paddle.full( shape=[sz, sz], dtype='float32', fill_value='-inf'), diagonal=1) mask = mask + mask_inf return mask def generate_padding_mask(self, x): padding_mask = paddle.equal(x, paddle.to_tensor(0, dtype=x.dtype)) return padding_mask def _reset_parameters(self): """Initiate parameters in the transformer model.""" for p in self.parameters(): if p.dim() > 1: xavier_uniform_(p) class TransformerEncoder(nn.Layer): """TransformerEncoder is a stack of N encoder layers Args: encoder_layer: an instance of the TransformerEncoderLayer() class (required). num_layers: the number of sub-encoder-layers in the encoder (required). norm: the layer normalization component (optional). """ def __init__(self, encoder_layer, num_layers): super(TransformerEncoder, self).__init__() self.layers = _get_clones(encoder_layer, num_layers) self.num_layers = num_layers def forward(self, src): """Pass the input through the endocder layers in turn. Args: src: the sequnce to the encoder (required). mask: the mask for the src sequence (optional). src_key_padding_mask: the mask for the src keys per batch (optional). """ output = src for i in range(self.num_layers): output = self.layers[i](output, src_mask=None, src_key_padding_mask=None) return output class TransformerDecoder(nn.Layer): """TransformerDecoder is a stack of N decoder layers Args: decoder_layer: an instance of the TransformerDecoderLayer() class (required). num_layers: the number of sub-decoder-layers in the decoder (required). norm: the layer normalization component (optional). """ def __init__(self, decoder_layer, num_layers): super(TransformerDecoder, self).__init__() self.layers = _get_clones(decoder_layer, num_layers) self.num_layers = num_layers def forward(self, tgt, memory, tgt_mask=None, memory_mask=None, tgt_key_padding_mask=None, memory_key_padding_mask=None): """Pass the inputs (and mask) through the decoder layer in turn. Args: tgt: the sequence to the decoder (required). memory: the sequnce from the last layer of the encoder (required). tgt_mask: the mask for the tgt sequence (optional). memory_mask: the mask for the memory sequence (optional). tgt_key_padding_mask: the mask for the tgt keys per batch (optional). memory_key_padding_mask: the mask for the memory keys per batch (optional). """ output = tgt for i in range(self.num_layers): output = self.layers[i]( output, memory, tgt_mask=tgt_mask, memory_mask=memory_mask, tgt_key_padding_mask=tgt_key_padding_mask, memory_key_padding_mask=memory_key_padding_mask) return output class TransformerEncoderLayer(nn.Layer): """TransformerEncoderLayer is made up of self-attn and feedforward network. This standard encoder layer is based on the paper "Attention Is All You Need". Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez, Lukasz Kaiser, and Illia Polosukhin. 2017. Attention is all you need. In Advances in Neural Information Processing Systems, pages 6000-6010. Users may modify or implement in a different way during application. Args: d_model: the number of expected features in the input (required). nhead: the number of heads in the multiheadattention models (required). dim_feedforward: the dimension of the feedforward network model (default=2048). dropout: the dropout value (default=0.1). """ def __init__(self, d_model, nhead, dim_feedforward=2048, attention_dropout_rate=0.0, residual_dropout_rate=0.1): super(TransformerEncoderLayer, self).__init__() self.self_attn = MultiheadAttention( d_model, nhead, dropout=attention_dropout_rate) self.conv1 = Conv2D( in_channels=d_model, out_channels=dim_feedforward, kernel_size=(1, 1)) self.conv2 = Conv2D( in_channels=dim_feedforward, out_channels=d_model, kernel_size=(1, 1)) self.norm1 = LayerNorm(d_model) self.norm2 = LayerNorm(d_model) self.dropout1 = Dropout(residual_dropout_rate) self.dropout2 = Dropout(residual_dropout_rate) def forward(self, src, src_mask=None, src_key_padding_mask=None): """Pass the input through the endocder layer. Args: src: the sequnce to the encoder layer (required). src_mask: the mask for the src sequence (optional). src_key_padding_mask: the mask for the src keys per batch (optional). """ src2 = self.self_attn( src, src, src, attn_mask=src_mask, key_padding_mask=src_key_padding_mask) src = src + self.dropout1(src2) src = self.norm1(src) src = paddle.transpose(src, [1, 2, 0]) src = paddle.unsqueeze(src, 2) src2 = self.conv2(F.relu(self.conv1(src))) src2 = paddle.squeeze(src2, 2) src2 = paddle.transpose(src2, [2, 0, 1]) src = paddle.squeeze(src, 2) src = paddle.transpose(src, [2, 0, 1]) src = src + self.dropout2(src2) src = self.norm2(src) return src class TransformerDecoderLayer(nn.Layer): """TransformerDecoderLayer is made up of self-attn, multi-head-attn and feedforward network. This standard decoder layer is based on the paper "Attention Is All You Need". Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez, Lukasz Kaiser, and Illia Polosukhin. 2017. Attention is all you need. In Advances in Neural Information Processing Systems, pages 6000-6010. Users may modify or implement in a different way during application. Args: d_model: the number of expected features in the input (required). nhead: the number of heads in the multiheadattention models (required). dim_feedforward: the dimension of the feedforward network model (default=2048). dropout: the dropout value (default=0.1). """ def __init__(self, d_model, nhead, dim_feedforward=2048, attention_dropout_rate=0.0, residual_dropout_rate=0.1): super(TransformerDecoderLayer, self).__init__() self.self_attn = MultiheadAttention( d_model, nhead, dropout=attention_dropout_rate) self.multihead_attn = MultiheadAttention( d_model, nhead, dropout=attention_dropout_rate) self.conv1 = Conv2D( in_channels=d_model, out_channels=dim_feedforward, kernel_size=(1, 1)) self.conv2 = Conv2D( in_channels=dim_feedforward, out_channels=d_model, kernel_size=(1, 1)) self.norm1 = LayerNorm(d_model) self.norm2 = LayerNorm(d_model) self.norm3 = LayerNorm(d_model) self.dropout1 = Dropout(residual_dropout_rate) self.dropout2 = Dropout(residual_dropout_rate) self.dropout3 = Dropout(residual_dropout_rate) def forward(self, tgt, memory, tgt_mask=None, memory_mask=None, tgt_key_padding_mask=None, memory_key_padding_mask=None): """Pass the inputs (and mask) through the decoder layer. Args: tgt: the sequence to the decoder layer (required). memory: the sequnce from the last layer of the encoder (required). tgt_mask: the mask for the tgt sequence (optional). memory_mask: the mask for the memory sequence (optional). tgt_key_padding_mask: the mask for the tgt keys per batch (optional). memory_key_padding_mask: the mask for the memory keys per batch (optional). """ tgt2 = self.self_attn( tgt, tgt, tgt, attn_mask=tgt_mask, key_padding_mask=tgt_key_padding_mask) tgt = tgt + self.dropout1(tgt2) tgt = self.norm1(tgt) tgt2 = self.multihead_attn( tgt, memory, memory, attn_mask=memory_mask, key_padding_mask=memory_key_padding_mask) tgt = tgt + self.dropout2(tgt2) tgt = self.norm2(tgt) # default tgt = paddle.transpose(tgt, [1, 2, 0]) tgt = paddle.unsqueeze(tgt, 2) tgt2 = self.conv2(F.relu(self.conv1(tgt))) tgt2 = paddle.squeeze(tgt2, 2) tgt2 = paddle.transpose(tgt2, [2, 0, 1]) tgt = paddle.squeeze(tgt, 2) tgt = paddle.transpose(tgt, [2, 0, 1]) tgt = tgt + self.dropout3(tgt2) tgt = self.norm3(tgt) return tgt def _get_clones(module, N): return LayerList([copy.deepcopy(module) for i in range(N)]) class PositionalEncoding(nn.Layer): """Inject some information about the relative or absolute position of the tokens in the sequence. The positional encodings have the same dimension as the embeddings, so that the two can be summed. Here, we use sine and cosine functions of different frequencies. .. math:: \text{PosEncoder}(pos, 2i) = sin(pos/10000^(2i/d_model)) \text{PosEncoder}(pos, 2i+1) = cos(pos/10000^(2i/d_model)) \text{where pos is the word position and i is the embed idx) Args: d_model: the embed dim (required). dropout: the dropout value (default=0.1). max_len: the max. length of the incoming sequence (default=5000). Examples: >>> pos_encoder = PositionalEncoding(d_model) """ def __init__(self, dropout, dim, max_len=5000): super(PositionalEncoding, self).__init__() self.dropout = nn.Dropout(p=dropout) pe = paddle.zeros([max_len, dim]) position = paddle.arange(0, max_len, dtype=paddle.float32).unsqueeze(1) div_term = paddle.exp( paddle.arange(0, dim, 2).astype('float32') * (-math.log(10000.0) / dim)) pe[:, 0::2] = paddle.sin(position * div_term) pe[:, 1::2] = paddle.cos(position * div_term) pe = paddle.unsqueeze(pe, 0) pe = paddle.transpose(pe, [1, 0, 2]) self.register_buffer('pe', pe) def forward(self, x): """Inputs of forward function Args: x: the sequence fed to the positional encoder model (required). Shape: x: [sequence length, batch size, embed dim] output: [sequence length, batch size, embed dim] Examples: >>> output = pos_encoder(x) """ x = x + self.pe[:paddle.shape(x)[0], :] return self.dropout(x) class PositionalEncoding_2d(nn.Layer): """Inject some information about the relative or absolute position of the tokens in the sequence. The positional encodings have the same dimension as the embeddings, so that the two can be summed. Here, we use sine and cosine functions of different frequencies. .. math:: \text{PosEncoder}(pos, 2i) = sin(pos/10000^(2i/d_model)) \text{PosEncoder}(pos, 2i+1) = cos(pos/10000^(2i/d_model)) \text{where pos is the word position and i is the embed idx) Args: d_model: the embed dim (required). dropout: the dropout value (default=0.1). max_len: the max. length of the incoming sequence (default=5000). Examples: >>> pos_encoder = PositionalEncoding(d_model) """ def __init__(self, dropout, dim, max_len=5000): super(PositionalEncoding_2d, self).__init__() self.dropout = nn.Dropout(p=dropout) pe = paddle.zeros([max_len, dim]) position = paddle.arange(0, max_len, dtype=paddle.float32).unsqueeze(1) div_term = paddle.exp( paddle.arange(0, dim, 2).astype('float32') * (-math.log(10000.0) / dim)) pe[:, 0::2] = paddle.sin(position * div_term) pe[:, 1::2] = paddle.cos(position * div_term) pe = paddle.transpose(paddle.unsqueeze(pe, 0), [1, 0, 2]) self.register_buffer('pe', pe) self.avg_pool_1 = nn.AdaptiveAvgPool2D((1, 1)) self.linear1 = nn.Linear(dim, dim) self.linear1.weight.data.fill_(1.) self.avg_pool_2 = nn.AdaptiveAvgPool2D((1, 1)) self.linear2 = nn.Linear(dim, dim) self.linear2.weight.data.fill_(1.) def forward(self, x): """Inputs of forward function Args: x: the sequence fed to the positional encoder model (required). Shape: x: [sequence length, batch size, embed dim] output: [sequence length, batch size, embed dim] Examples: >>> output = pos_encoder(x) """ w_pe = self.pe[:paddle.shape(x)[-1], :] w1 = self.linear1(self.avg_pool_1(x).squeeze()).unsqueeze(0) w_pe = w_pe * w1 w_pe = paddle.transpose(w_pe, [1, 2, 0]) w_pe = paddle.unsqueeze(w_pe, 2) h_pe = self.pe[:paddle.shape(x).shape[-2], :] w2 = self.linear2(self.avg_pool_2(x).squeeze()).unsqueeze(0) h_pe = h_pe * w2 h_pe = paddle.transpose(h_pe, [1, 2, 0]) h_pe = paddle.unsqueeze(h_pe, 3) x = x + w_pe + h_pe x = paddle.transpose( paddle.reshape(x, [x.shape[0], x.shape[1], x.shape[2] * x.shape[3]]), [2, 0, 1]) return self.dropout(x) class Embeddings(nn.Layer): def __init__(self, d_model, vocab, padding_idx, scale_embedding): super(Embeddings, self).__init__() self.embedding = nn.Embedding(vocab, d_model, padding_idx=padding_idx) w0 = np.random.normal(0.0, d_model**-0.5, (vocab, d_model)).astype(np.float32) self.embedding.weight.set_value(w0) self.d_model = d_model self.scale_embedding = scale_embedding def forward(self, x): if self.scale_embedding: x = self.embedding(x) return x * math.sqrt(self.d_model) return self.embedding(x) class Beam(): ''' Beam search ''' def __init__(self, size, device=False): self.size = size self._done = False # The score for each translation on the beam. self.scores = paddle.zeros((size, ), dtype=paddle.float32) self.all_scores = [] # The backpointers at each time-step. self.prev_ks = [] # The outputs at each time-step. self.next_ys = [paddle.full((size, ), 0, dtype=paddle.int64)] self.next_ys[0][0] = 2 def get_current_state(self): "Get the outputs for the current timestep." return self.get_tentative_hypothesis() def get_current_origin(self): "Get the backpointers for the current timestep." return self.prev_ks[-1] @property def done(self): return self._done def advance(self, word_prob): "Update beam status and check if finished or not." num_words = word_prob.shape[1] # Sum the previous scores. if len(self.prev_ks) > 0: beam_lk = word_prob + self.scores.unsqueeze(1).expand_as(word_prob) else: beam_lk = word_prob[0] flat_beam_lk = beam_lk.reshape([-1]) best_scores, best_scores_id = flat_beam_lk.topk(self.size, 0, True, True) # 1st sort self.all_scores.append(self.scores) self.scores = best_scores # bestScoresId is flattened as a (beam x word) array, # so we need to calculate which word and beam each score came from prev_k = best_scores_id // num_words self.prev_ks.append(prev_k) self.next_ys.append(best_scores_id - prev_k * num_words) # End condition is when top-of-beam is EOS. if self.next_ys[-1][0] == 3: self._done = True self.all_scores.append(self.scores) return self._done def sort_scores(self): "Sort the scores." return self.scores, paddle.to_tensor( [i for i in range(int(self.scores.shape[0]))], dtype='int32') def get_the_best_score_and_idx(self): "Get the score of the best in the beam." scores, ids = self.sort_scores() return scores[1], ids[1] def get_tentative_hypothesis(self): "Get the decoded sequence for the current timestep." if len(self.next_ys) == 1: dec_seq = self.next_ys[0].unsqueeze(1) else: _, keys = self.sort_scores() hyps = [self.get_hypothesis(k) for k in keys] hyps = [[2] + h for h in hyps] dec_seq = paddle.to_tensor(hyps, dtype='int64') return dec_seq def get_hypothesis(self, k): """ Walk back to construct the full hypothesis. """ hyp = [] for j in range(len(self.prev_ks) - 1, -1, -1): hyp.append(self.next_ys[j + 1][k]) k = self.prev_ks[j][k] return list(map(lambda x: x.item(), hyp[::-1]))