train_movie_dialog_sw_gpt.py

import time
import numpy as np
import pandas as pd
import pickle as pkl
import byte_pair_encoding as bpe

import torch
import torch_gpt as gpt_module

# Define the weight update step for multiple sub-batches. #
def sub_batch_train_step(
    model, sub_batch_sz, x_encode, x_output, 
    optimizer, seg_length=None, grad_clip=1.0):
    ce_loss_fn = torch.nn.CrossEntropyLoss(reduction="none")
    
    batch_size = x_encode.shape[0]
    if batch_size <= sub_batch_sz:
        sub_batch = 1
    elif batch_size % sub_batch_sz == 0:
        sub_batch = int(batch_size / sub_batch_sz)
    else:
        sub_batch = int(batch_size / sub_batch_sz) + 1
    avg_batch_loss = 0.0
    
    optimizer.zero_grad()
    for n_sub in range(sub_batch):
        id_st = n_sub*sub_batch_sz
        if n_sub != (sub_batch-1):
            id_en = (n_sub+1)*sub_batch_sz
        else:
            id_en = batch_size
        
        tmp_encode = torch.tensor(
            x_encode[id_st:id_en, :], dtype=torch.long)
        tmp_output = torch.tensor(
            x_output[id_st:id_en, :], dtype=torch.long)
        
        if torch.cuda.is_available():
            tmp_encode = tmp_encode.to("cuda")
            tmp_output = tmp_output.to("cuda")
        
        # Accumulate the gradients. #
        tmp_ce_losses  = model.compute_ce_loss(
            tmp_encode, tmp_output, seg_len=seg_length)
        sub_batch_loss = tmp_ce_losses / batch_size
        avg_batch_loss += sub_batch_loss.item()
        sub_batch_loss.backward()
    
    # Update using the optimizer. #
    torch.nn.utils.clip_grad_norm_(
        model.parameters(), grad_clip)
    optimizer.step()
    return avg_batch_loss

# Model Parameters. #
batch_size = 256
sub_batch  = 64
seq_length = 31
num_heads  = 4
num_layers = 3

gradient_clip = 1.00
maximum_iter  = 20000
restore_flag  = False
save_step     = 250
warmup_steps  = 5000
display_step  = 50

prob_keep = 0.9
prob_drop = 1.0 - prob_keep

hidden_size = 256
ffwd_size   = 4*hidden_size
cooling_step = 250

model_ckpt_dir  = "PyTorch_Models/dialog_sw_torch_gpt_module"
train_loss_file = "train_loss_dialog_sw_torch_gpt_module.csv"

# Load the data. #
tmp_pkl_file = "../../Data/movie_dialogs/"
tmp_pkl_file += "movie_dialogues_subword.pkl"
with open(tmp_pkl_file, "rb") as tmp_load_file:
    data_tuple = pkl.load(tmp_load_file)
    subword_vocab = pkl.load(tmp_load_file)
    idx_2_subword = pkl.load(tmp_load_file)
    subword_2_idx = pkl.load(tmp_load_file)

# Filter the dataset. #
filtered_data = []
for tmp_data in data_tuple:
    tot_len = len(tmp_data[0]) + len(tmp_data[1])
    if tot_len > 1 and tot_len <= (seq_length-1):
        filtered_data.append(tmp_data)
del tmp_data, data_tuple

data_tuple = filtered_data
vocab_size = len(subword_vocab)
print("Subword Vocabulary Size:", str(vocab_size) + ".")
del filtered_data

num_data  = len(data_tuple)
SOS_token = subword_2_idx["<SOS>"]
EOS_token = subword_2_idx["<EOS>"]
PAD_token = subword_2_idx["<PAD>"]
UNK_token = subword_2_idx["<UNK>"]
print("Total of", num_data, "rows loaded.")

# Set the number of threads to use. #
torch.set_num_threads(1)

# Build the GPT network. #
print("Building the GPT Model.")
start_time = time.time()

gpt_model = gpt_module.GPTDecoder(
    num_layers, num_heads, 
    hidden_size, ffwd_size, vocab_size, 
    seq_length, rate1=0.0, rate2=prob_drop)
if torch.cuda.is_available():
    gpt_model.to("cuda")

gpt_optimizer = torch.optim.AdamW(
    gpt_model.parameters())

elapsed_time = (time.time()-start_time) / 60
print("GPT Model Built (" + str(elapsed_time), "mins).")

if restore_flag:
    ckpt = torch.load(model_ckpt_dir)
    n_iter = ckpt["step"]
    
    gpt_model.load_state_dict(ckpt['model_state_dict'])
    gpt_optimizer.load_state_dict(ckpt['optimizer_state_dict'])
    
    train_loss_df = pd.read_csv(train_loss_file)
    train_loss_list = [tuple(
        train_loss_df.iloc[x].values) \
        for x in range(len(train_loss_df))]
else:
    print("Training a new model.")
    n_iter = 0
    train_loss_list = []

# Train the GPT model. #
tmp_out_seq = np.zeros(
    [batch_size, seq_length+1], dtype=np.int32)

# Warmup learning schedule. #
step_min = float(max(n_iter, warmup_steps))**(-0.5)
learning_rate = float(hidden_size)**(-0.5) * step_min

print("-" * 50)
print("Training the GPT Network", 
      "(" + str(n_iter) + " iterations).")
print(str(num_data), "training samples.")
print("-" * 50)

# Update the neural network's weights. #
tot_loss = 0.0
start_tm = time.time()
while n_iter < maximum_iter:
    step_min = float(max(n_iter, warmup_steps))**(-0.5)
    learning_rate = float(hidden_size)**(-0.5) * step_min
    
    for tmp_opt_group in gpt_optimizer.param_groups:
        tmp_opt_group["lr"] = learning_rate
    
    # Select a sample from the data. #
    batch_sample = np.random.choice(
        num_data, size=batch_size, replace=False)
    
    tmp_out_seq[:, :] = PAD_token
    for n_index in range(batch_size):
        tmp_index = batch_sample[n_index]
        tmp_i_idx = data_tuple[tmp_index][0]
        tmp_o_idx = data_tuple[tmp_index][1]
        
        tmp_p_idx = tmp_i_idx + [SOS_token]
        tmp_p_idx += tmp_o_idx + [EOS_token]
        
        n_input = len(tmp_p_idx)
        tmp_out_seq[n_index, :n_input] = tmp_p_idx
    
    # Set the training data. #
    tmp_input  = tmp_out_seq[:, :-1]
    tmp_output = tmp_out_seq[:, 1:]
    
    tmp_loss = sub_batch_train_step(
        gpt_model, sub_batch, 
        tmp_input, tmp_output, 
        gpt_optimizer, seg_length=seq_length)
    
    n_iter += 1
    tot_loss += tmp_loss
    if n_iter % display_step == 0:
        end_tm = time.time()
        
        avg_loss = tot_loss / display_step
        tot_loss = 0.0
        elapsed_tm = (end_tm - start_tm) / 60
        
        sample_id = np.random.choice(num_data)
        tmp_data  = data_tuple[sample_id]
        tmp_i_idx = tmp_data[0]
        tmp_o_idx = tmp_data[1]
        tmp_i_tok = bpe.bp_decode(tmp_i_idx, idx_2_subword)
        tmp_o_tok = bpe.bp_decode(tmp_o_idx, idx_2_subword)
        n_tokens  = len(tmp_i_idx)
        
        tmp_test_in = tmp_i_idx + [SOS_token]
        tmp_test_in = np.array(tmp_test_in).reshape((1, -1))

        infer_in = torch.tensor(
            tmp_test_in, dtype=torch.long)
        if torch.cuda.is_available():
            infer_in = infer_in.to("cuda")
        
        tmp_infer = gpt_model.infer(infer_in)
        if torch.cuda.is_available():
            tmp_infer = tmp_infer.detach().cpu()
        del tmp_data

        tmp_in_phrase  = " ".join(
            tmp_i_tok).replace("<", "").replace(">", "")
        tmp_out_phrase  = " ".join(
            tmp_o_tok).replace("<", "").replace(">", "")
        
        gen_tokens = tmp_infer[0].numpy()
        gen_phrase = bpe.bp_decode(
            gen_tokens, idx_2_subword)
        gen_phrase = " ".join(
            gen_phrase).replace("<", "").replace(">", "")
        
        gen_reply = gen_tokens[n_tokens:]
        gen_reply = bpe.bp_decode(
            gen_reply, idx_2_subword)
        gen_reply = " ".join(
            gen_reply).replace("<", "").replace(">", "")
        
        print("Iteration", str(n_iter) + ".")
        print("Elapsed Time:", str(elapsed_tm), "mins.")
        print("Gradient Clip:", str(gradient_clip) + ".")
        print("Learning Rate:", str(learning_rate) + ".")
        print("Average Loss:", str(avg_loss) + ".")
        
        print("")
        print("Input Phrase:")
        print(tmp_in_phrase)
        print("Generated Phrase:")
        print(gen_phrase)
        print("Generated Reply:")
        print(gen_reply)
        print("Actual Response:")
        print(tmp_out_phrase)
        del n_tokens
        
        train_loss_list.append((n_iter, avg_loss))
        start_tm = time.time()
        print("-" * 50)
    
    # Save the model. #
    if n_iter % save_step == 0:
        # Save the model. #
        torch.save({
            'step': n_iter,
            'model_state_dict': gpt_model.state_dict(),
            'optimizer_state_dict': gpt_optimizer.state_dict()
            }, model_ckpt_dir)
        print("Saved model to:", model_ckpt_dir)
        
        tmp_df_losses = pd.DataFrame(
            train_loss_list, columns=["n_iter", "xent_loss"])
        tmp_df_losses.to_csv(train_loss_file, index=False)
        del tmp_df_losses
    
    # Cool the GPU. #
    if n_iter % cooling_step == 0:
        print("Cooling GPU for 2 minutes.")
        time.sleep(120)
        print("Resume Training.")
        print("-" * 50)