train_iter.py

'''=================================================
@IDE    ：Pycharm
@Author ：Qingyong Li
@Date   ：2019/11/22
=================================================='''
import torch
from torch import nn, optim
from torch.autograd import Variable
from torch.utils.data import DataLoader
from torchvision import datasets, transforms

import cnn

# 定义一些超参数

batch_size = 128
learning_rate = 0.01
num_epoches = 20

# 数据预处理。transforms.ToTensor()将图片转换成PyTorch中处理的对象Tensor,并且进行标准化（数据在0~1之间）
# transforms.Normalize()做归一化。它进行了减均值，再除以标准差。两个参数分别是均值和标准差
# transforms.Compose()函数则是将各种预处理的操作组合到了一起

data_tf = transforms.Compose(
    [transforms.ToTensor(),
     transforms.Normalize([0.5], [0.5])])



# 数据集的下载器

train_dataset = datasets.MNIST(root='./data', train=True, transform=data_tf, download=True)

test_dataset = datasets.MNIST(root='./data', train=False, transform=data_tf)

train_loader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True)

test_loader = DataLoader(test_dataset, batch_size=batch_size, shuffle=False)



# 选择模型

model = cnn.CNN()

# model = net.Activation_Net(28 * 28, 300, 100, 10)

# model = net.Batch_Net(28 * 28, 300, 100, 10)

if torch.cuda.is_available():
    print("CUDA is available")
    model = model.cuda()



# 定义损失函数和优化器

criterion = nn.CrossEntropyLoss()

optimizer = optim.SGD(model.parameters(), lr=learning_rate)



# 训练模型
for i in range(num_epoches):
    epoch = 0

    for data in train_loader:

        img, label = data

    # img = img.view(img.size(0), -1)

        img = Variable(img)

        if torch.cuda.is_available():

            img = img.cuda()

            label = label.cuda()

        else:

            img = Variable(img)

            label = Variable(label)

        out = model(img)

        loss = criterion(out, label)

        print_loss = loss.data.item()
        optimizer.zero_grad()

        loss.backward()

        optimizer.step()

        epoch+=1

        #if epoch%50 == 0:

            #print('epoch: {}, loss: {:.4}'.format(epoch, loss.data.item()))



    # 模型评估

    model.eval()

    eval_loss = 0

    eval_acc = 0

    for data in test_loader:

        img, label = data

    # img = img.view(img.size(0), -1)

        img = Variable(img)

        if torch.cuda.is_available():

            img = img.cuda()

            label = label.cuda()



        out = model(img)

        loss = criterion(out, label)

        eval_loss += loss.data.item()*label.size(0)

        _, pred = torch.max(out, 1)

        num_correct = (pred == label).sum()

        eval_acc += num_correct.item()
    print('EPOCH: ',i+1)
    print('Test Loss: {:.6f}, Acc: {:.6f}'.format(

        eval_loss / (len(test_dataset)),

        eval_acc / (len(test_dataset))

    ))
    i+=1
#保存模型
torch.save(model, 'CNN_for_MNIST.pth')