target_x = batch['Dispx'].to(device) target_y = batch['Dispy'].to(device) target = torch.cat([target_x,target_y],1).to(device)

这段代码的目的是将训练数据中的`Dispx`和`Dispy`两个特征合并为一个目标张量`target`，以便在训练过程中使用。

首先，代码从`batch`中获取`Dispx`和`Dispy`两个特征，并将它们移动到指定的设备上（例如GPU）以进行加速计算。然后，通过使用`torch.cat()`函数，将`target_x`和`target_y`在维度1上进行拼接，生成一个新的张量`target`。拼接的结果是将`target_x`和`target_y`按列连接在一起，形成一个形状为(batch_size, 2)的张量。

最终，将合并后的目标张量`target`也移动到指定的设备上，以便与模型进行计算和训练。

相关问题

train_x_tensor = torch.from_numpy(train_x).type(torch.FloatTensor).to(DEVICE) # (B, N, F, T) train_target_tensor = torch.from_numpy(train_target).type(torch.FloatTensor).to(DEVICE) # (B, N, T) train_dataset = torch.utils.data.TensorDataset(train_x_tensor, train_target_tensor) train_loader = torch.utils.data.DataLoader(train_dataset, batch_size=batch_size, shuffle=shuffle)是什么意思

这段代码是将 numpy 数组转换为 PyTorch 的张量，并将其放置在 GPU 上进行训练。具体来说，它完成以下操作：

- 将训练数据集（train_x 和 train_target）转换为 PyTorch 的张量。
- 将张量类型转换为 FloatTensor（在 PyTorch 中，FloatTensor 是默认的张量类型）。
- 将张量放置在指定的设备（DEVICE）上，这里通常指的是 GPU。
- 使用 PyTorch 的 TensorDataset 类将训练数据集打包成一个数据集对象。
- 使用 PyTorch 的 DataLoader 类将数据集对象转换为数据加载器，用于批量加载训练数据。batch_size 参数指定了每个批次的大小，shuffle 参数指定了是否需要对数据进行随机重排。

LDAM损失函数pytorch代码如下：class LDAMLoss(nn.Module): def init(self, cls_num_list, max_m=0.5, weight=None, s=30): super(LDAMLoss, self).init() m_list = 1.0 / np.sqrt(np.sqrt(cls_num_list)) m_list = m_list * (max_m / np.max(m_list)) m_list = torch.cuda.FloatTensor(m_list) self.m_list = m_list assert s > 0 self.s = s if weight is not None: weight = torch.FloatTensor(weight).cuda() self.weight = weight self.cls_num_list = cls_num_list def forward(self, x, target): index = torch.zeros_like(x, dtype=torch.uint8) index_float = index.type(torch.cuda.FloatTensor) batch_m = torch.matmul(self.m_list[None, :], index_float.transpose(1,0)) # 0,1 batch_m = batch_m.view((16, 1)) # size=(batch_size, 1) (-1,1) x_m = x - batch_m output = torch.where(index, x_m, x) if self.weight is not None: output = output * self.weight[None, :] target = torch.flatten(target) # 将 target 转换成 1D Tensor logit = output * self.s return F.cross_entropy(logit, target, weight=self.weight) 模型部分参数如下：# 设置全局参数 model_lr = 1e-5 BATCH_SIZE = 16 EPOCHS = 50 DEVICE = torch.device('cuda:0' if torch.cuda.is_available() else 'cpu') use_amp = True use_dp = True classes = 7 resume = None CLIP_GRAD = 5.0 Best_ACC = 0 #记录最高得分 use_ema=True model_ema_decay=0.9998 start_epoch=1 seed=1 seed_everything(seed) # 数据增强 mixup mixup_fn = Mixup( mixup_alpha=0.8, cutmix_alpha=1.0, cutmix_minmax=None, prob=0.1, switch_prob=0.5, mode='batch', label_smoothing=0.1, num_classes=classes) # 读取数据集 dataset_train = datasets.ImageFolder('/home/adminis/hpy/ConvNextV2_Demo/RAF-DB/RAF/train', transform=transform) dataset_test = datasets.ImageFolder("/home/adminis/hpy/ConvNextV2_Demo/RAF-DB/RAF/valid", transform=transform_test)# 导入数据 train_loader = torch.utils.data.DataLoader(dataset_train, batch_size=BATCH_SIZE, shuffle=True,drop_last=True) test_loader = torch.utils.data.DataLoader(dataset_test, batch_size=BATCH_SIZE, shuffle=False) 帮我用pytorch实现模型在模型训练中使用LDAM损失函数

好的，以下是使用LDAM损失函数训练模型的Pytorch代码：

import torch
import torch.nn as nn
import torch.nn.functional as F
import numpy as np
from torchvision import datasets, transforms
from ldam_loss import LDAMLoss

# 定义模型
class MyModel(nn.Module):
    def __init__(self, num_classes):
        super(MyModel, self).__init__()
        self.num_classes = num_classes
        self.features = nn.Sequential(
            nn.Conv2d(3, 32, kernel_size=3, stride=1, padding=1),
            nn.BatchNorm2d(32),
            nn.ReLU(inplace=True),
            nn.MaxPool2d(kernel_size=2, stride=2),
            nn.Conv2d(32, 64, kernel_size=3, stride=1, padding=1),
            nn.BatchNorm2d(64),
            nn.ReLU(inplace=True),
            nn.MaxPool2d(kernel_size=2, stride=2),
            nn.Conv2d(64, 128, kernel_size=3, stride=1, padding=1),
            nn.BatchNorm2d(128),
            nn.ReLU(inplace=True),
            nn.MaxPool2d(kernel_size=2, stride=2),
        )
        self.classifier = nn.Sequential(
            nn.Linear(128 * 4 * 4, 256),
            nn.ReLU(inplace=True),
            nn.Linear(256, num_classes),
        )

    def forward(self, x):
        x = self.features(x)
        x = x.view(x.size(0), -1)
        x = self.classifier(x)
        return x

# 设置超参数
model_lr = 1e-4
BATCH_SIZE = 16
EPOCHS = 50
DEVICE = torch.device('cuda:0' if torch.cuda.is_available() else 'cpu')
use_amp = True
use_dp = True
classes = 7
resume = None
CLIP_GRAD = 5.0
Best_ACC = 0
use_ema = True
model_ema_decay = 0.9998
start_epoch = 1
seed = 1

# 设置随机种子
def seed_everything(seed):
    torch.manual_seed(seed)
    torch.cuda.manual_seed_all(seed)
    np.random.seed(seed)
seed_everything(seed)

# 定义数据增强
transform = transforms.Compose([
    transforms.Resize(224),
    transforms.RandomHorizontalFlip(),
    transforms.RandomRotation(10),
    transforms.ToTensor(),
    transforms.Normalize(mean=[0.485, 0.456, 0.406],
                         std=[0.229, 0.224, 0.225])
])
transform_test = transforms.Compose([
    transforms.Resize(224),
    transforms.ToTensor(),
    transforms.Normalize(mean=[0.485, 0.456, 0.406],
                         std=[0.229, 0.224, 0.225])
])

# 定义数据集
dataset_train = datasets.ImageFolder('/home/adminis/hpy/ConvNextV2_Demo/RAF-DB/RAF/train', transform=transform)
dataset_test = datasets.ImageFolder("/home/adminis/hpy/ConvNextV2_Demo/RAF-DB/RAF/valid", transform=transform_test)

# 定义数据加载器
train_loader = torch.utils.data.DataLoader(dataset_train, batch_size=BATCH_SIZE, shuffle=True, drop_last=True)
test_loader = torch.utils.data.DataLoader(dataset_test, batch_size=BATCH_SIZE, shuffle=False)

# 定义模型及优化器
model = MyModel(num_classes=classes).to(DEVICE)
optimizer = torch.optim.Adam(model.parameters(), lr=model_lr)

# 使用LDAM损失函数
cls_num_list = [dataset_train.targets.count(i) for i in range(classes)]
criterion = LDAMLoss(cls_num_list=cls_num_list, max_m=0.5, weight=None, s=30)

# 训练模型
for epoch in range(start_epoch, EPOCHS+1):
    model.train()
    for i, (data, target) in enumerate(train_loader):
        data, target = data.to(DEVICE), target.to(DEVICE)
        mixup_data, mixup_target = mixup_fn(data, target)  # 数据增强
        optimizer.zero_grad()
        output = model(mixup_data)
        loss = criterion(output, mixup_target)
        if use_dp:
            loss.backward()
            torch.nn.utils.clip_grad_norm_(model.parameters(), CLIP_GRAD)
        else:
            with amp.scale_loss(loss, optimizer) as scaled_loss:
                scaled_loss.backward()
                torch.nn.utils.clip_grad_norm_(amp.master_params(optimizer), CLIP_GRAD)
        optimizer.step()
    if use_ema:
        ema_model = ModelEMA(model, decay=model_ema_decay)
        ema_model.update(model)
    else:
        ema_model = None
    test_acc = test(model, test_loader, DEVICE)
    if test_acc > Best_ACC:
        Best_ACC = test_acc
        save_checkpoint({
            'epoch': epoch,
            'state_dict': model.state_dict(),
            'optimizer': optimizer.state_dict(),
            'Best_ACC': Best_ACC,
        }, is_best=True)