如何指定多块GPU卡进行训练-数据并行

news2024/11/13 8:54:33

训练代码：

train.py

import torch
import torch.nn as nn
import torch.optim as optim
from torch.utils.data import DataLoader, Dataset
import torch.nn.functional as F

# 假设我们有一个简单的文本数据集
class TextDataset(Dataset):
    def __init__(self, texts, labels, vocab):
        self.texts = texts
        self.labels = labels
        self.vocab = vocab

    def __len__(self):
        return len(self.texts)

    def __getitem__(self, idx):
        text = self.texts[idx]
        label = self.labels[idx]
        # 将文本转换为索引
        text_indices = [self.vocab.get(word, self.vocab['<UNK>']) for word in text.split()]
        return torch.tensor(text_indices, dtype=torch.long), torch.tensor(label, dtype=torch.long)

# 定义一个简单的LSTM分类器
class LSTMClassifier(nn.Module):
    def __init__(self, vocab_size, embedding_dim, hidden_dim, output_dim):
        super(LSTMClassifier, self).__init__()
        self.embedding = nn.Embedding(vocab_size, embedding_dim)
        self.lstm = nn.LSTM(embedding_dim, hidden_dim, batch_first=True)
        self.fc = nn.Linear(hidden_dim, output_dim)

    def forward(self, x):
        embedded = self.embedding(x)
        _, (hidden, _) = self.lstm(embedded)
        output = self.fc(hidden[-1])
        return output

# 构建词汇表
vocab = {'<PAD>': 0, '<UNK>': 1, 'I': 2, 'love': 3, 'this': 4, 'movie': 5, 'is': 6, 'terrible': 7}
vocab_size = len(vocab)

# 示例数据
texts = ["I love this movie", "This movie is terrible"]
labels = [1, 0]  # 1表示正面情感，0表示负面情感

# 创建数据集和数据加载器
dataset = TextDataset(texts, labels, vocab)
dataloader = DataLoader(dataset, batch_size=2, shuffle=True, collate_fn=lambda x: (torch.nn.utils.rnn.pad_sequence([item[0] for item in x], batch_first=True), torch.stack([item[1] for item in x])))

# 实例化模型
embedding_dim = 50
hidden_dim = 50
output_dim = 2
model = LSTMClassifier(vocab_size, embedding_dim, hidden_dim, output_dim)

# 使用DataParallel包装模型
model = nn.DataParallel(model)

# 将模型移动到GPU
model = model.cuda()

# 定义损失函数和优化器
criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(model.parameters(), lr=0.001)

# 训练步骤
model.train()
for epoch in range(10):  # 训练10个epoch
    for inputs, labels in dataloader:
        inputs, labels = inputs.cuda(), labels.cuda()
        optimizer.zero_grad()
        outputs = model(inputs)
        loss = criterion(outputs, labels)
        loss.backward()
        optimizer.step()
    print(f"Epoch {epoch+1}, Loss: {loss.item()}")

print("训练完成")

# 测试模型
model.eval()
test_texts = ["I love this movie", "This movie is terrible"]
test_dataset = TextDataset(test_texts, [1, 0], vocab)
test_dataloader = DataLoader(test_dataset, batch_size=2, shuffle=False, collate_fn=lambda x: (torch.nn.utils.rnn.pad_sequence([item[0] for item in x], batch_first=True), torch.stack([item[1] for item in x])))

with torch.no_grad():
    for inputs, labels in test_dataloader:
        inputs, labels = inputs.cuda(), labels.cuda()
        outputs = model(inputs)
        predictions = torch.argmax(F.softmax(outputs, dim=1), dim=1)
        print(f"Predictions: {predictions.cpu().numpy()}, Labels: {labels.cpu().numpy()}")

执行命令：

export CUDA_VISIBLE_DEVICES=0,2
python train.py

GPU监控

训练前
在这里插入图片描述
训练中

Epoch 1, Loss: 0.7198400497436523
Epoch 2, Loss: 0.6889444589614868
Epoch 3, Loss: 0.6591541767120361
Epoch 4, Loss: 0.630306601524353
Epoch 5, Loss: 0.6022476553916931
Epoch 6, Loss: 0.5748419761657715
Epoch 7, Loss: 0.5479871034622192
Epoch 8, Loss: 0.5216072201728821
Epoch 9, Loss: 0.4956483840942383
Epoch 10, Loss: 0.47007784247398376
训练完成
Predictions: [1 0], Labels: [1 0]

结论

export CUDA_VISIBLE_DEVICES=0,2与nn.DataParallel(model)结合的方法是正确的

为什么需要指定 CUDA_VISIBLE_DEVICES

在多GPU系统中，默认情况下，PyTorch 会尝试使用所有可用的GPU进行训练。
通过设置 CUDA_VISIBLE_DEVICES 环境变量，用于控制哪些GPU对当前进程可见，PyTorch 只会使用这些可见的GPU进行训练。
通过设置环境变量，你可以在不修改代码的情况下控制使用的GPU。这使得代码更加简洁和通用，不需要在代码中硬编码GPU的选择逻辑。
总的来说：通过设置 CUDA_VISIBLE_DEVICES 环境变量，你可以灵活地控制哪些GPU对当前进程可见，从而避免资源冲突、简化代码并更好地管理多GPU资源。这是使用 torch.nn.DataParallel 进行多GPU训练时的一种常见做法。