我是神經網路的新手，我正在嘗試在自定義資料集（單個目錄中的貓和狗影像）上訓練 CNN 模型。所以我想我在這里做了大多數教程中非常常見的事情，但以防萬一我會在這里提供我的完整代碼。
首先我生成要處理的 .csv 檔案：
import os
import torch
device = ("cuda" if torch.cuda.is_available() else "cpu")
train_df = pd.DataFrame(columns=["img_name","label"])
train_df["img_name"] = os.listdir("train/")
for idx, i in enumerate(os.listdir("train/")):
if "cat" in i:
train_df["label"][idx] = 0
if "dog" in i:
train_df["label"][idx] = 1
train_df.to_csv (r'train_csv.csv', index = False, header=True)
然后我準備資料集：
from torch.utils.data import Dataset
import pandas as pd
import os
from PIL import Image
import torch
class CatsAndDogsDataset(Dataset):
def __init__(self, root_dir, annotation_file, transform=None):
self.root_dir = root_dir
self.annotations = pd.read_csv(annotation_file)
self.transform = transform
def __len__(self):
return len(self.annotations)
def __getitem__(self, index):
img_id = self.annotations.iloc[index, 0]
img = Image.open(os.path.join(self.root_dir, img_id)).convert("RGB")
y_label = torch.tensor(float(self.annotations.iloc[index, 1]))
if self.transform is not None:
img = self.transform(img)
return (img, y_label)
這是我的模型：
import torch.nn as nn
import torchvision.models as models
class CNN(nn.Module):
def __init__(self, train_CNN=False, num_classes=1):
super(CNN, self).__init__()
self.train_CNN = train_CNN
self.inception = models.inception_v3(pretrained=True, aux_logits=False)
self.inception.fc = nn.Linear(self.inception.fc.in_features, num_classes)
self.relu = nn.ReLU()
self.dropout = nn.Dropout(0.5)
self.sigmoid = nn.Sigmoid()
def forward(self, images):
features = self.inception(images)
return self.sigmoid(self.dropout(self.relu(features))).squeeze(1)
這是我的超引數、轉換和資料加載器：
from torch.utils.data import DataLoader
import torchvision.transforms as transforms
num_epochs = 10
learning_rate = 0.00001
train_CNN = False
batch_size = 32
shuffle = True
pin_memory = True
num_workers = 0
transform = transforms.Compose(
[
transforms.Resize((356, 356)),
transforms.RandomCrop((299, 299)),
transforms.ToTensor(),
transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),
]
)
dataset = CatsAndDogsDataset("train","train_csv.csv",transform=transform)
print(len(dataset))
train_set, validation_set = torch.utils.data.random_split(dataset,[162,40])
train_loader = DataLoader(dataset=train_set, shuffle=shuffle, batch_size=batch_size,num_workers=num_workers,pin_memory=pin_memory)
validation_loader = DataLoader(dataset=validation_set, shuffle=shuffle, batch_size=batch_size,num_workers=num_workers, pin_memory=pin_memory)
model = CNN().to(device)
criterion = nn.BCELoss()
optimizer = torch.optim.Adam(model.parameters(), lr=learning_rate)
for name, param in model.inception.named_parameters():
if "fc.weight" in name or "fc.bias" in name:
param.requires_grad = True
else:
param.requires_grad = train_CNN
和準確性檢查：
def check_accuracy(loader, model):
if loader == train_loader:
print("Checking accuracy on training data")
else:
print("Checking accuracy on validation data")
num_correct = 0
num_samples = 0
model.eval()
with torch.no_grad():
for x, y in loader:
x = x.to(device=device)
y = y.to(device=device)
scores = model(x)
predictions = torch.tensor([1.0 if i >= 0.5 else 0.0 for i in scores]).to(device)
num_correct = (predictions == y).sum()
num_samples = predictions.size(0)
print(
f"Got {num_correct} / {num_samples} with accuracy {float(num_correct)/float(num_samples)*100:.2f}"
)
model.train()
return f"{float(num_correct)/float(num_samples)*100:.2f}"
這是我的訓練功能：
from tqdm import tqdm
def train():
model.train()
for epoch in range(num_epochs):
loop = tqdm(train_loader, total = len(train_loader), leave = True)
if epoch % 2 == 0:
loop.set_postfix(val_acc = check_accuracy(validation_loader, model))
for imgs, labels in loop:
imgs = imgs.to(device)
labels = labels.to(device)
outputs = model(imgs)
loss = criterion(outputs, labels)
optimizer.zero_grad()
loss.backward()
optimizer.step()
loop.set_description(f"Epoch [{epoch}/{num_epochs}]")
loop.set_postfix(loss = loss.item())
if __name__ == "__main__":
train()
0%| | 0/6 [00:00<?, ?it/s]Checking accuracy on validation data
0%| | 0/6 [01:13<?, ?it/s, val_acc=60.00]Got 24 / 40 with accuracy 60.00
Epoch [0/10]: 100%|██████████| 6/6 [06:02<00:00, 60.39s/it, loss=0.693]
Epoch [1/10]: 100%|██████████| 6/6 [04:49<00:00, 48.23s/it, loss=0.693]
...
Epoch [8/10]: 100%|██████████| 6/6 [06:07<00:00, 61.29s/it, loss=0.693]
Epoch [9/10]: 100%|██████████| 6/6 [04:55<00:00, 49.19s/it, loss=0.781]
該模型得到了很好的訓練，但是當我嘗試使用它進行預測時，每次在我的 Jupyter Notebooks 中運行最后一段時，我都會得到不同的結果：
model.eval()
img = Image.open('train/cat.22.png').convert("RGB")
img_t = transform(img)
batch_t = torch.unsqueeze(img_t, 0)
out = model(batch_t)
print(out)
張量（[0.5276]，grad_fn=）
張量（[0.5000]，grad_fn=）
張量（[0.5064]，grad_fn=）
等。每次對同一影像產生不同的結果。這是正常的嗎？為什么會發生這種情況？
uj5u.com熱心網友回復：
我沒有看到你加載你的訓練模型。這意味著每次初始化CNN模塊時，inception.fc層都將使用隨機權重進行初始化，這很可能是每次推理得到不同結果的原因。
編輯：您的轉換管道中有一個隨機轉換，即RandomCrop.
uj5u.com熱心網友回復：
根據有關使用的這個答案model.eval()，我相信您可能希望確保將代碼單元的下半部分包裝在with torch.no_grad():背景關系中。我認為除非在該背景關系中，否則它可能仍在學習/更新引數。
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