If there are any faults in the loss calculation during training fix it according to the correct formula, *code*: import torch
import torch.nn as nn
import torch.nn.functional as F
import json
import math
from torch.nn.utils.rnn import pad_sequence
from torch.utils.data import DataLoader, Dataset
from collections import Counter
from tqdm import tqdm


# ---------- Device Configuration ----------
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

# ---------- Utility Functions ----------
def positional_encoding(seq_len, d_model, device):
    pos = torch.arange(seq_len, dtype=torch.float, device=device).unsqueeze(1)
    div_term = torch.exp(torch.arange(0, d_model, 2).float() * (-math.log(10000.0) / d_model)).to(device)
    pe = torch.zeros(seq_len, d_model, device=device)
    pe[:, 0::2] = torch.sin(pos * div_term)
    pe[:, 1::2] = torch.cos(pos * div_term)
    return pe.unsqueeze(0)

# ---------- Model Definitions ----------
class TransformerExpert(nn.Module):
    def __init__(self, input_size, d_model, output_size, nhead, dim_feedforward, num_encoder_layers=1):
        super(TransformerExpert, self).__init__()
        self.d_model = d_model
        self.input_fc = nn.Linear(input_size, d_model)
        encoder_layer = nn.TransformerEncoderLayer(d_model=d_model, nhead=nhead, dim_feedforward=dim_feedforward, batch_first=True)
        self.transformer_encoder = nn.TransformerEncoder(encoder_layer, num_layers=num_encoder_layers)
        self.output_fc = nn.Linear(d_model, output_size)

    def forward(self, x):
        x = self.input_fc(x) + positional_encoding(x.size(1), self.d_model, x.device)
        transformer_output = self.transformer_encoder(x)
        output = self.output_fc(transformer_output)
        return output

class GatingNetwork(nn.Module):
    def __init__(self, input_feature_dim, num_experts, hidden_dims=None, dropout_rate=0.0):
        super(GatingNetwork, self).__init__()
        layers = []
        last_dim = input_feature_dim
        

        if hidden_dims is not None:
            for hidden_dim in hidden_dims:
                layers.append(nn.Linear(last_dim, hidden_dim))
                layers.append(nn.ReLU())
                if dropout_rate > 0.0:
                    layers.append(nn.Dropout(dropout_rate))
                last_dim = hidden_dim
        
        layers.append(nn.Linear(last_dim, num_experts))
        self.fc_layers = nn.Sequential(*layers)
        self.softmax = nn.Softmax(dim=1)
    
    def forward(self, x):
        x = x.mean(dim=1)
        x = self.fc_layers(x)
        return self.softmax(x)

class MixtureOfTransformerExperts(nn.Module):
    def __init__(self, input_size, d_model, output_size, nhead, dim_feedforward, num_experts, num_encoder_layers=1):
        super(MixtureOfTransformerExperts, self).__init__()
        self.num_experts = num_experts
        self.output_size = output_size
        self.experts = nn.ModuleList([TransformerExpert(input_size, d_model, output_size, nhead, dim_feedforward, num_encoder_layers) for _ in range(num_experts)])
        self.gating_network = GatingNetwork(d_model, num_experts)

    def forward(self, x):
        gating_scores = self.gating_network(x)

        expert_outputs = [expert(x) for expert in self.experts]
        stacked_expert_outputs = torch.stack(expert_outputs)

        expanded_gating_scores = gating_scores.unsqueeze(2).unsqueeze(3)
        expanded_gating_scores = expanded_gating_scores.expand(-1, -1, x.size(1), self.output_size)
        expanded_gating_scores = expanded_gating_scores.transpose(0, 1)

        mixed_output = torch.sum(stacked_expert_outputs * expanded_gating_scores, dim=0)
        return mixed_output

class MoETransformerModel(nn.Module):
    def __init__(self, vocab_size, d_model, moe):
        super(MoETransformerModel, self).__init__()
        self.embedding = nn.Embedding(num_embeddings=vocab_size, embedding_dim=d_model)
        self.moe = moe
        self.dropout = nn.Dropout(p=0.125)

    def forward(self, x):
        embedded = self.dropout(self.embedding(x))
        return self.moe(embedded)

# ---------- Dataset Definitions ----------
class QAJsonlDataset(Dataset):
    def __init__(self, path, seq_len):
        self.seq_len = seq_len
        self.pairs = self.load_data(path)
        self.vocab, self.idx2token = self.build_vocab([word for pair in self.pairs for sublist in pair for word in sublist])
        self.tokenized_pairs = [(self.tokenize(q), self.tokenize(a)) for q, a in self.pairs]

    def load_data(self, path):
        pairs = []
        with open(path, "r", encoding="utf-8") as f:
            for line in f:
                data = json.loads(line.strip())
                question, answer = data.get("instruction", ""), data.get("response", "")
                pairs.append((question.split(), answer.split()))
        return pairs

    def tokenize(self, words):
        tokens = [self.vocab.get(w, self.vocab["<unk>"]) for w in words]
        if len(tokens) < self.seq_len:
            tokens.append(self.vocab["<eos>"])
            tokens.extend([self.vocab["<pad>"]] * (self.seq_len - len(tokens)))
        else:
            tokens = tokens[:self.seq_len - 1] + [self.vocab["<eos>"]]
        return tokens

    def build_vocab(self, words):
        vocab = {"<unk>": 0, "<pad>": 1, "<eos>": 2}
        start_index = len(vocab)
        counts = Counter(words)
    
        for word, _ in counts.most_common():
            if word not in vocab:
                vocab[word] = len(vocab)

        idx2token = {idx: token for token, idx in vocab.items()}
        return vocab, idx2token
        
    def __len__(self):
        return len(self.tokenized_pairs)

    def __getitem__(self, idx):
        tokenized_question, tokenized_answer = self.tokenized_pairs[idx]
        return torch.tensor(tokenized_question, dtype=torch.long), torch.tensor(tokenized_answer, dtype=torch.long)

def collate_fn(batch):
    questions, answers = zip(*batch)
    questions = pad_sequence(questions, batch_first=True, padding_value=0)
    answers = pad_sequence(answers, batch_first=True, padding_value=0)
    return questions, answers

# ---------- Training and Inference Functions ----------
def train_model(model, criterion, optimizer, num_epochs, data_loader):
    model.train()
    for epoch in range(num_epochs):
        total_loss = 0
        progress_bar = tqdm(enumerate(data_loader), total=len(data_loader), desc=f"Epoch {epoch+1}", leave=False)
        for i, (inputs, targets) in progress_bar:
            inputs, targets = inputs.to(device), targets.to(device)
            optimizer.zero_grad()
            predictions = model(inputs)
            predictions = predictions.view(-1, predictions.size(-1))
            targets = targets.view(-1)
            loss = criterion(predictions, targets)
            loss.backward()
            torch.nn.utils.clip_grad_norm_(model.parameters(), max_norm=1.0)
            optimizer.step()
            total_loss += loss.item()
            progress_bar.set_postfix({"Loss": loss.item()})
        average_loss = total_loss / len(data_loader.dataset)
        print(f"Epoch {epoch+1}, Average Loss: {average_loss}")

def generate_text(model, dataset, seed_text, num_generate, temperature=1.0):
    model.eval()
    
    generated_tokens = []

    # Initial sequence (prefix) to start the generation process
    input_sequence = [dataset.vocab.get(word, dataset.vocab["<pad>"]) for word in seed_text.split()]
    current_sequence = torch.tensor(input_sequence, dtype=torch.long).unsqueeze(0)
    current_sequence = current_sequence.to(device)

    # Generate num_generate tokens
    for _ in range(num_generate):
        # Forward pass through the model
        with torch.no_grad():
            output = model(current_sequence)
        
        # Get probabilities, apply temperature scaling, and sample from the distribution
        probabilities = F.softmax(output[:, -1, :] / temperature, dim=-1).detach()
        next_token_idx = torch.multinomial(probabilities, 1).item()

        # Append token to the current sequence and to the generated tokens
        generated_tokens.append(next_token_idx)
        current_sequence = torch.cat((current_sequence, torch.tensor([[next_token_idx]])), 1).to(device)
    
    # Convert tokens to words
    generated_text = " ".join([dataset.idx2token.get(token, "<unk>") for token in generated_tokens])
    return generated_text

def count_tokens_in_dataset(dataset):
    return sum([len(pair[0]) + len(pair[1]) for pair in dataset.pairs])

def count_parameters(model):
    return sum(p.numel() for p in model.parameters() if p.requires_grad)

# ---------- Hyperparameters and Model Instantiation ----------
# Transformer :
d_model = 768
nhead = 6
dim_feedforward = 384
num_encoder_layers = 12
num_experts = 4
hidden_dims = [768, 256, 128]
dropout_rate = 0.5

# Gating Network :
gating_network = GatingNetwork(
    input_feature_dim=d_model,
    num_experts=num_experts,
    hidden_dims=hidden_dims,
    dropout_rate=dropout_rate,
)

# Dataset :
path_to_dataset = "C:/Users/L14/Documents/Projets/Easy-MoE/Easy-MoE/data/Databricks-2K.jsonl"
seq_len = 32
dataset = QAJsonlDataset(path_to_dataset, seq_len)
data_loader = DataLoader(dataset, batch_size=seq_len, shuffle=True, collate_fn=collate_fn, pin_memory=True)
    
num_tokens = count_tokens_in_dataset(dataset)
print(f"Total number of tokens in the dataset: {num_tokens}")

vocab_size = len(dataset.vocab)

moe = MixtureOfTransformerExperts(
    input_size=d_model,
    d_model=d_model,
    output_size=vocab_size,
    nhead=nhead,
    dim_feedforward=dim_feedforward,
    num_experts=num_experts,
    num_encoder_layers=num_encoder_layers
).to(device)

moe_transformer_model = MoETransformerModel(vocab_size, d_model, moe).to(device)

# Count of total parameters :
total_params = count_parameters(moe_transformer_model)
print(f"Total trainable parameters: {total_params}")

# ---------- Training ----------
num_epochs = 1
learning_rate = 1e-8

criterion = nn.CrossEntropyLoss(label_smoothing=0.1)
optimizer = torch.optim.AdamW(moe_transformer_model.parameters(), lr=learning_rate, weight_decay=0.01)

# Train the model
train_model(moe_transformer_model, criterion, optimizer, num_epochs, data_loader)

# ---------- Inference ----------
def interactive_text_generation(model, dataset, max_length=32, temperature=0.2):
    while True:
        try:
            # Get user input
            seed_text = input("Enter seed text (type 'quit' to exit and save the model): ").strip()
            
            # Check if user wants to quit the interaction
            if seed_text.lower() == 'quit':
                print("Exiting text generation mode.")
                break
            
            # Check if the seed text is not empty
            if seed_text:
                generated_text = generate_text(model, dataset, seed_text, max_length, temperature)
                print("Generated Text: ", generated_text)
            else:
                print("Seed text cannot be empty. Please enter some text.")
                
        except KeyboardInterrupt:
            # Handle the interrupt signal to exit gracefully
            print("\nReceived interrupt signal. Exiting text generation mode.")
            break
        except Exception as e:
            # Handle other exceptions and prevent the loop from crashing
            print(f"An error occurred: {e}. Try again.")

interactive_text_generation(moe_transformer_model, dataset)

# ---------- Save Trained Model ----------
torch.save(moe_transformer_model.state_dict(), "MoE_Transformer-Instruct-X4.pth")