import torch
import torch.nn as nn
import torch.optim as optim
import matplotlib.pyplot as plt
import numpy as np
# 数据集:字符序列预测(Hello -> Elloh)
char_set = list("hello")
char_to_idx = {c: i for i, c in enumerate(char_set)}
idx_to_char = {i: c for i, c in enumerate(char_set)}
# 数据准备
input_str = "hello"
target_str = "elloh"
input_data = [char_to_idx[c] for c in input_str]
target_data = [char_to_idx[c] for c in target_str]
# 转换为独热编码
input_one_hot = np.eye(len(char_set))[input_data]
# 转换为 PyTorch Tensor
inputs = torch.tensor(input_one_hot, dtype=torch.float32)
targets = torch.tensor(target_data, dtype=torch.long)
# 模型超参数
input_size = len(char_set)
hidden_size = 8
output_size = len(char_set)
num_epochs = 200
learning_rate = 0.1
# 定义 RNN 模型
class RNNModel(nn.Module):
def __init__(self, input_size, hidden_size, output_size):
super(RNNModel, self).__init__()
self.rnn = nn.RNN(input_size, hidden_size, batch_first=True)
self.fc = nn.Linear(hidden_size, output_size)
def forward(self, x, hidden):
out, hidden = self.rnn(x, hidden)
out = self.fc(out) # 应用全连接层
return out, hidden
model = RNNModel(input_size, hidden_size, output_size)
# 定义损失函数和优化器
criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(model.parameters(), lr=learning_rate)
# 训练 RNN
losses = []
hidden = None # 初始隐藏状态为 None
for epoch in range(num_epochs):
optimizer.zero_grad()
# 前向传播
outputs, hidden = model(inputs.unsqueeze(0), hidden)
hidden = hidden.detach() # 防止梯度爆炸
# 计算损失
loss = criterion(outputs.view(-1, output_size), targets)
loss.backward()
optimizer.step()
losses.append(loss.item())
if (epoch + 1) % 20 == 0:
print(f"Epoch [{epoch + 1}/{num_epochs}], Loss: {loss.item():.4f}")
# 测试 RNN
with torch.no_grad():
test_hidden = None
test_output, _ = model(inputs.unsqueeze(0), test_hidden)
predicted = torch.argmax(test_output, dim=2).squeeze().numpy()
print("Input sequence: ", ''.join([idx_to_char[i] for i in input_data]))
print("Predicted sequence: ", ''.join([idx_to_char[i] for i in predicted]))
# 可视化损失
plt.plot(losses, label="Training Loss")
plt.xlabel("Epoch")
plt.ylabel("Loss")
plt.title("RNN Training Loss Over Epochs")
plt.legend()
plt.show(),在这个代码里加入gpu加速