def get_mean_and_std(dataset): '''Compute the mean and std value of dataset.''' dataloader = torch.utils.data.DataLoader(dataset, batch_size=1, shuffle=True, num_workers=2) mean = torch.zeros(3) std = torch.zeros(3) print('==> Computing mean and std..') for inputs, targets in dataloader: for i in range(3): mean[i] += inputs[:,i,:,:].mean() std[i] += inputs[:,i,:,:].std() mean.div_(len(dataset)) std.div_(len(dataset)) return mean,这段代码是干什么的
时间: 2024-02-07 13:02:39 浏览: 137
这段代码是用来计算给定数据集的均值和标准差的。它首先创建一个数据加载器(`dataloader`),用于加载数据集,并将每个数据样本单独作为一个批次(`batch_size=1`)进行处理。然后,它在循环中计算每个通道(在这里是3个通道)的均值和标准差,并将结果存储在`mean`和`std`张量中。最后,它将每个通道的总和除以数据集的大小(`len(dataset)`),以获得该通道的平均值和标准差,并返回这些值。
相关问题
import torch from torch.utils.data import Dataset from tools import ReadIntArray, OneHotData class SSQDataset(Dataset): def __init__(self, file_path, my_detection, sample_nums): self.file_path = file_path self.my_detection = my_detection self.sample_nums = sample_nums self.my_list = ReadIntArray(self.file_path) def __getitem__(self, my_index): data_list = [] target_list = [] start_index = my_index for sample_num in range(self.sample_nums): data_list.append(self.my_list[start_index + sample_num]) if self.my_detection in self.my_list[start_index + self.sample_nums]: target_list = [1, 0] else: target_list = [0, 1] data_list = OneHotData(data_list) data_list = torch.tensor(data_list, dtype=torch.float32) target_list = torch.tensor(target_list, dtype=torch.float32) return data_list, target_list def __len__(self): return len(self.my_list) - self.sample_nums
这段代码定义了一个名为SSQDataset的数据集类,用于读取文件并将其转换为模型可接受的数据格式。其中:
- `file_path`表示数据文件路径;
- `my_detection`表示要检测的目标,例如在双色球中是要预测的红球还是蓝球;
- `sample_nums`表示每个样本中包含的数据点数;
- `ReadIntArray`函数用于读取数据文件并将其转换为整数列表;
- `__getitem__`函数用于获取某个索引位置的数据,并将其转换为模型可接受的数据格式,同时将该数据对应的目标标签也转换为模型可接受的格式;
- `OneHotData`函数用于将原始数据转换为独热编码格式;
- `__len__`函数用于返回数据集的长度。
这个数据集类可以用于训练模型,例如:
```python
from torch.utils.data import DataLoader
from model import MyModel
dataset = SSQDataset(file_path='data/ssq.txt', my_detection='red', sample_nums=5)
dataloader = DataLoader(dataset, batch_size=32, shuffle=True)
model = MyModel()
for data, target in dataloader:
output = model(data)
loss = compute_loss(output, target)
optimizer.zero_grad()
loss.backward()
optimizer.step()
```
这里假设模型类为`MyModel`,使用PyTorch内置的`DataLoader`类将数据集分成批次进行训练。在每个批次中,将数据输入模型,计算损失并进行反向传播和优化。
dataset = 'image/' sampler_loader = torch.utils.data.DataLoader( datasets.ImageFolder(dataset, transform = transforms.Compose([ transforms.Resize((224, 224)), transforms.ToTensor(), transforms.Normalize(mean = [0.485, 0.456, 0.406], std = [0.229, 0.224, 0.225]) ]))) unnormalize = NormalizeInverse(mean = [0.485, 0.456, 0.406], std = [0.229, 0.224, 0.225]) device = torch.device("cuda" if torch.cuda.is_available() else "cpu") model = vgg11_bn(pretrained = True) model = model.to(device) fullgrad = FullGrad(model) simple_fullgrad = FullGradSimple(model) save_path = 'result' if os.path.isdir(save_path): os.mkdir(save_path) def compute_saliency_and_save(): for idx, (data, target) in enumerate(sampler_loader): data, target = data.to(device).requires_grad_(), target.to(device) # compute the saliency maps for the input data cam = fullgrad.fullgrad(data) cam_simple = simple_fullgrad.fullgrad(data) for i in range(data.size(0)): filename = save_path + str((idx + 1) * (i+1)) filename_simple = filename + "_simple" image = unnormalize(data[i,:,:,:].cpu()) save_saliency_map(image, cam[i,:,:,:], filename + ".jpg") save_saliency_map(image, cam_simple[i,:,:,:], filename_simple + ".jpg") if __name__ == "__main__": compute_saliency_and_save() 详细解释程序
这段程序是一个计算图像数据的显著性图并保存的过程。下面是对程序的详细解释:
1. 导入必要的库:
```python
import torch
import torchvision.datasets as datasets
import torchvision.transforms as transforms
from models import vgg11_bn
from fullgrad import FullGrad, FullGradSimple
from utils import NormalizeInverse, save_saliency_map
import os
```
2. 定义数据集和数据加载器:
```python
dataset = 'image/'
sampler_loader = torch.utils.data.DataLoader(
datasets.ImageFolder(dataset, transform = transforms.Compose([
transforms.Resize((224, 224)),
transforms.ToTensor(),
transforms.Normalize(mean = [0.485, 0.456, 0.406], std = [0.229, 0.224, 0.225])
])))
```
这里使用了`datasets.ImageFolder`来加载数据集,`transform`参数指定了对图像进行的预处理操作,包括将图像大小调整为224x224,转换为张量和归一化。
3. 定义反归一化操作:
```python
unnormalize = NormalizeInverse(mean = [0.485, 0.456, 0.406], std = [0.229, 0.224, 0.225])
```
`NormalizeInverse`是一个自定义的类,用于将经过归一化处理的张量反转回原始图像。
4. 检查设备是否支持CUDA并定义模型:
```python
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
model = vgg11_bn(pretrained = True)
model = model.to(device)
```
这里使用`torch.cuda.is_available()`来检查设备是否支持CUDA,并将模型移动到相应的设备(GPU或CPU)。
5. 定义FullGrad和Simple FullGrad对象:
```python
fullgrad = FullGrad(model)
simple_fullgrad = FullGradSimple(model)
```
`FullGrad`和`FullGradSimple`是自定义的类,用于计算图像数据的显著性图。
6. 定义结果保存路径:
```python
save_path = 'result'
if os.path.isdir(save_path):
os.mkdir(save_path)
```
如果保存路径不存在,则创建一个新的。
7. 定义计算显著性图并保存的函数:
```python
def compute_saliency_and_save():
for idx, (data, target) in enumerate(sampler_loader):
data, target = data.to(device).requires_grad_(), target.to(device)
cam = fullgrad.fullgrad(data)
cam_simple = simple_fullgrad.fullgrad(data)
for i in range(data.size(0)):
filename = save_path + str((idx + 1) * (i+1))
filename_simple = filename + "_simple"
image = unnormalize(data[i,:,:,:].cpu())
save_saliency_map(image, cam[i,:,:,:], filename + ".jpg")
save_saliency_map(image, cam_simple[i,:,:,:], filename_simple + ".jpg")
```
这个函数会遍历数据加载器中的每个数据,将其移动到设备上,并计算其对应的显著性图。然后,将图像、显著性图和保存路径传递给`save_saliency_map`函数以保存显著性图。
8. 主函数:
```python
if __name__ == "__main__":
compute_saliency_and_save()
```
当脚本被直接执行时,会调用`compute_saliency_and_save`函数来计算和保存显著性图。
总结:这段程序用于计算图像数据的显著性图并保存,它使用了预训练的VGG-11模型和FullGrad算法。程序首先加载数据集并进行预处理,然后将模型移动到合适的设备上。接下来,使用FullGrad和Simple FullGrad算法计算每个图像的显著性图,并将结果保存到指定路径下。
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