โมเดล Seq2seq (ลำดับต่อลำดับ) ด้วย PyTorch

from __future__ import unicode_literals, print_function, division
import torch
import torch.nn as nn
import torch.optim as optim
import torch.nn.functional as F

import numpy as np
import pandas as pd

import os
import re
import random

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

SOS_token = 0
EOS_token = 1
MAX_LENGTH = 20

#initialize Lang Class
class Lang:
   def __init__(self):
       #initialize containers to hold the words and corresponding index
       self.word2index = {}
       self.word2count = {}
       self.index2word = {0: "SOS", 1: "EOS"}
       self.n_words = 2  # Count SOS and EOS

#split a sentence into words and add it to the container
   def addSentence(self, sentence):
       for word in sentence.split(' '):
           self.addWord(word)

#If the word is not in the container, the word will be added to it, else, update the word counter
   def addWord(self, word):
       if word not in self.word2index:
           self.word2index[word] = self.n_words
           self.word2count[word] = 1
           self.index2word[self.n_words] = word
           self.n_words += 1
       else:
           self.word2count[word] += 1

#Normalize every sentence
def normalize_sentence(df, lang):
   sentence = df[lang].str.lower()
   sentence = sentence.str.replace('[^A-Za-z\s]+', '')
   sentence = sentence.str.normalize('NFD')
   sentence = sentence.str.encode('ascii', errors='ignore').str.decode('utf-8')
   return sentence

def read_sentence(df, lang1, lang2):
   sentence1 = normalize_sentence(df, lang1)
   sentence2 = normalize_sentence(df, lang2)
   return sentence1, sentence2

def read_file(loc, lang1, lang2):
   df = pd.read_csv(loc, delimiter='\t', header=None, names=[lang1, lang2])
   return df

def process_data(lang1,lang2):
   df = read_file('text/%s-%s.txt' % (lang1, lang2), lang1, lang2)
   print("Read %s sentence pairs" % len(df))
   sentence1, sentence2 = read_sentence(df, lang1, lang2)

   source = Lang()
   target = Lang()
   pairs = []
   for i in range(len(df)):
       if len(sentence1[i].split(' ')) < MAX_LENGTH and len(sentence2[i].split(' ')) < MAX_LENGTH:
           full = [sentence1[i], sentence2[i]]
           source.addSentence(sentence1[i])
           target.addSentence(sentence2[i])
           pairs.append(full)

   return source, target, pairs

def indexesFromSentence(lang, sentence):
   return [lang.word2index[word] for word in sentence.split(' ')]

def tensorFromSentence(lang, sentence):
   indexes = indexesFromSentence(lang, sentence)
   indexes.append(EOS_token)
   return torch.tensor(indexes, dtype=torch.long, device=device).view(-1, 1)

def tensorsFromPair(input_lang, output_lang, pair):
   input_tensor = tensorFromSentence(input_lang, pair[0])
   target_tensor = tensorFromSentence(output_lang, pair[1])
   return (input_tensor, target_tensor)

class Encoder(nn.Module):
   def __init__(self, input_dim, hidden_dim, embbed_dim, num_layers):
       super(Encoder, self).__init__()

       #set the encoder input dimesion , embbed dimesion, hidden dimesion, and number of layers
       self.input_dim = input_dim
       self.embbed_dim = embbed_dim
       self.hidden_dim = hidden_dim
       self.num_layers = num_layers

       #initialize the embedding layer with input and embbed dimention
       self.embedding = nn.Embedding(input_dim, self.embbed_dim)
       #intialize the GRU to take the input dimetion of embbed, and output dimention of hidden and
       #set the number of gru layers
       self.gru = nn.GRU(self.embbed_dim, self.hidden_dim, num_layers=self.num_layers)

   def forward(self, src):
       embedded = self.embedding(src).view(1,1,-1)
       outputs, hidden = self.gru(embedded)
       return outputs, hidden

class Decoder(nn.Module):
   def __init__(self, output_dim, hidden_dim, embbed_dim, num_layers):
       super(Decoder, self).__init__()

#set the encoder output dimension, embed dimension, hidden dimension, and number of layers
       self.embbed_dim = embbed_dim
       self.hidden_dim = hidden_dim
       self.output_dim = output_dim
       self.num_layers = num_layers

# initialize every layer with the appropriate dimension. For the decoder layer, it will consist of an embedding, GRU, a Linear layer and a Log softmax activation function.
       self.embedding = nn.Embedding(output_dim, self.embbed_dim)
       self.gru = nn.GRU(self.embbed_dim, self.hidden_dim, num_layers=self.num_layers)
       self.out = nn.Linear(self.hidden_dim, output_dim)
       self.softmax = nn.LogSoftmax(dim=1)

   def forward(self, input, hidden):
# reshape the input to (1, batch_size)
       input = input.view(1, -1)
       embedded = F.relu(self.embedding(input))
       output, hidden = self.gru(embedded, hidden)
       prediction = self.softmax(self.out(output[0]))
       return prediction, hidden

class Seq2Seq(nn.Module):
   def __init__(self, encoder, decoder, device, MAX_LENGTH=MAX_LENGTH):
       super().__init__()

#initialize the encoder and decoder
       self.encoder = encoder
       self.decoder = decoder
       self.device = device

   def forward(self, source, target, teacher_forcing_ratio=0.5):
       input_length = source.size(0) #get the input length (number of words in sentence)
       batch_size = target.shape[1]
       target_length = target.shape[0]
       vocab_size = self.decoder.output_dim

#initialize a variable to hold the predicted outputs
       outputs = torch.zeros(target_length, batch_size, vocab_size).to(self.device)

#encode every word in a sentence
       for i in range(input_length):
           encoder_output, encoder_hidden = self.encoder(source[i])

#use the encoder's hidden layer as the decoder hidden
       decoder_hidden = encoder_hidden.to(device)

#add a token before the first predicted word
       decoder_input = torch.tensor([SOS_token], device=device)  # SOS

#topk is used to get the top K value over a list
#predict the output word from the current target word. If we enable the teaching force, then the next decoder input is the next word, else, use the decoder output highest value.
       for t in range(target_length):
           decoder_output, decoder_hidden = self.decoder(decoder_input, decoder_hidden)
           outputs[t] = decoder_output
           teacher_force = random.random() < teacher_forcing_ratio
           topv, topi = decoder_output.topk(1)
           input = (target[t] if teacher_force else topi)
           if(teacher_force == False and input.item() == EOS_token):
               break

       return outputs

teacher_forcing_ratio = 0.5

def clacModel(model, input_tensor, target_tensor, model_optimizer, criterion):
   model_optimizer.zero_grad()

   input_length = input_tensor.size(0)
   loss = 0
   epoch_loss = 0
   # print(input_tensor.shape)

   output = model(input_tensor, target_tensor)

   num_iter = output.size(0)
   print(num_iter)

#calculate the loss from a predicted sentence with the expected result
   for ot in range(num_iter):
       loss += criterion(output[ot], target_tensor[ot])

   loss.backward()
   model_optimizer.step()
   epoch_loss = loss.item() / num_iter

   return epoch_loss

def trainModel(model, source, target, pairs, num_iteration=20000):
   model.train()

   optimizer = optim.SGD(model.parameters(), lr=0.01)
   criterion = nn.NLLLoss()
   total_loss_iterations = 0

   training_pairs = [tensorsFromPair(source, target, random.choice(pairs))
                     for i in range(num_iteration)]

   for iter in range(1, num_iteration+1):
       training_pair = training_pairs[iter - 1]
       input_tensor = training_pair[0]
       target_tensor = training_pair[1]

       loss = clacModel(model, input_tensor, target_tensor, optimizer, criterion)

       total_loss_iterations += loss

       if iter % 5000 == 0:
           avarage_loss= total_loss_iterations / 5000
           total_loss_iterations = 0
           print('%d %.4f' % (iter, avarage_loss))

   torch.save(model.state_dict(), 'mytraining.pt')
   return model

def evaluate(model, input_lang, output_lang, sentences, max_length=MAX_LENGTH):
   with torch.no_grad():
       input_tensor = tensorFromSentence(input_lang, sentences[0])
       output_tensor = tensorFromSentence(output_lang, sentences[1])

       decoded_words = []

       output = model(input_tensor, output_tensor)
       # print(output_tensor)

       for ot in range(output.size(0)):
           topv, topi = output[ot].topk(1)
           # print(topi)

           if topi[0].item() == EOS_token:
               decoded_words.append('')
               break
           else:
               decoded_words.append(output_lang.index2word[topi[0].item()])
   return decoded_words

def evaluateRandomly(model, source, target, pairs, n=10):
   for i in range(n):
       pair = random.choice(pairs)
       print('source {}'.format(pair[0]))
       print('target {}'.format(pair[1]))
       output_words = evaluate(model, source, target, pair)
       output_sentence = ' '.join(output_words)
       print('predicted {}'.format(output_sentence))

lang1 = 'eng'
lang2 = 'ind'
source, target, pairs = process_data(lang1, lang2)

randomize = random.choice(pairs)
print('random sentence {}'.format(randomize))

#print number of words
input_size = source.n_words
output_size = target.n_words
print('Input : {} Output : {}'.format(input_size, output_size))

embed_size = 256
hidden_size = 512
num_layers = 1
num_iteration = 100000

#create encoder-decoder model
encoder = Encoder(input_size, hidden_size, embed_size, num_layers)
decoder = Decoder(output_size, hidden_size, embed_size, num_layers)

model = Seq2Seq(encoder, decoder, device).to(device)

#print model
print(encoder)
print(decoder)

model = trainModel(model, source, target, pairs, num_iteration)
evaluateRandomly(model, source, target, pairs)

random sentence ['tom is finishing his work', 'tom sedang menyelesaikan pekerjaannya']
Input : 3551 Output : 4253
Encoder(
  (embedding): Embedding(3551, 256)
  (gru): GRU(256, 512)
)
Decoder(
  (embedding): Embedding(4253, 256)
  (gru): GRU(256, 512)
  (out): Linear(in_features=512, out_features=4253, bias=True)
  (softmax): LogSoftmax()
)
5000 4.0906
10000 3.9129
15000 3.8171
20000 3.8369
25000 3.8199
30000 3.7957
75000 3.7044