往期学习资料推荐:1.Pytorch实战笔记_GoAI的博客-CSDN博客
2.Pytorch入门教程_GoAI的博客-CSDN博客
本系列目录: PyTorch学习笔记(一):PyTorch环境安装
PyTorch学习笔记(二):简介与基础知识
PyTorch学习笔记(三):PyTorch主要组成模块
PyTorch学习笔记(四):PyTorch基础实战
PyTorch学习笔记(五):模型定义、修改、保存
后续继续更新!!!!
1 深度学习步骤 (1)数据预处理:通过专门的数据加载,通过批训练提高模型表现,每次训练读取固定数量的样本输入到模型中进行训练
(2)深度神经网络搭建:逐层搭建,实现特定功能的层(如积层、池化层、批正则化层、LSTM层等)
(3)损失函数和优化器的设定:保证反向传播能够在用户定义的模型结构上实现
(4)模型训练:使用并行计算加速训练,将数据按批加载,放入GPU中训练,对损失函数反向传播回网络最前面的层,同时使用优化器调整网络参数
2 基本配置
- 导入相关的包
import os
import numpy as py
import torch
import torch.nn as nn
from torch.utils.data import Dataset, DataLoader
import torch.optim as optimizer
- 统一设置超参数:batch size、初始学习率、训练次数、GPU配置
# set batch size
batch_size = 16# 初始学习率
lr = 1e-4# 训练次数
max_epochs = 100# 配置GPU
device = torch.device("cuda:1" if torch.cuda.is_available() else "cpu")
devicedevice(type='cuda', index=1)
3 数据读入
- 读取方式:通过Dataset+DataLoader的方式加载数据,Dataset定义好数据的格式和数据变换形式,DataLoader用iterative的方式不断读入批次数据。
- 自定义Dataset类:实现
__init___
、__getitem__
、__len__
函数
-
torch.utils.data.DataLoader
参数:
- batch_size:样本是按“批”读入的,表示每次读入的样本数
- num_workers:表示用于读取数据的进程数
- shuffle:是否将读入的数据打乱
- drop_last:对于样本最后一部分没有达到批次数的样本,使其不再参与训练
通过
Module
类构造模型,实例化模型之后,可完成模型构造# 构造多层感知机
class MLP(nn.Module):
def __init__(self, **kwargs):
super(MLP, self).__init__(**kwargs)
self.hidden = nn.Linear(784, 256)
self.act = nn.ReLU()
self.output = nn.Linear(256, 10)def forward(self, X):
o = self.act(self.hidden(x))
return self.output(o)x = torch.rand(2, 784)
net = MLP()
print(x)
net(x)
tensor([[0.8924, 0.9624, 0.3262,..., 0.8376, 0.1889, 0.9060],
[0.3609, 0.8005, 0.5175,..., 0.6255, 0.1462, 0.9846]])tensor([[-0.0902,0.0199,0.0677, -0.0679,0.0799,0.0826,0.0628,0.1809,
-0.2387,0.0366],
[-0.2271,0.0056, -0.0984, -0.0432, -0.0160, -0.0038,0.0953,0.0545,
-0.1530, -0.0214]], grad_fn=)
4.2 神经网络常见的层
- 不含模型参数的层
# 构造一个输入减去均值后输出的层
class MyLayer(nn.Module):
def __init__(self, **kwargs):
super(MyLayer, self).__init__(**kwargs)def forward(self, x):
return x - x.mean()
x = torch.tensor([0, 5, 10, 15, 20], dtype=torch.float)
layer = MyLayer()
layer(x)
tensor([-10.,-5.,0.,5.,10.])
- 含模型参数的层:如果一个
Tensor
是Parameter
,那么它会?动被添加到模型的参数列表里
# 使用ParameterList定义参数的列表
class MyListDense(nn.Module):
def __init__(self):
super(MyListDense, self).__init__()
self.params = nn.ParameterList(
[nn.Parameter(torch.randn(4, 4)) for i in range(3)])
self.params.append(nn.Parameter(torch.randn(4, 1)))def forward(self, x):
for i in range(len(self.params)):
x = torch.mm(x, self.params[i])
return x
net = MyListDense()
print(net)
MyListDense(
(params): ParameterList(
(0): Parameter containing: [torch.FloatTensor of size 4x4]
(1): Parameter containing: [torch.FloatTensor of size 4x4]
(2): Parameter containing: [torch.FloatTensor of size 4x4]
(3): Parameter containing: [torch.FloatTensor of size 4x1]
)
)
# 使用ParameterDict定义参数的字典
class MyDictDense(nn.Module):
def __init__(self):
super(MyDictDense, self).__init__()
self.params = nn.ParameterDict({
'linear1': nn.Parameter(torch.randn(4, 4)),
'linear2': nn.Parameter(torch.randn(4, 1))
})
# 新增参数linear3
self.params.update({'linear3': nn.Parameter(torch.randn(4, 2))}) def forward(self, x, choice='linear1'):
return torch.mm(x, self.params[choice])net = MyDictDense()
print(net)
MyDictDense(
(params): ParameterDict(
(linear1): Parameter containing: [torch.FloatTensor of size 4x4]
(linear2): Parameter containing: [torch.FloatTensor of size 4x1]
(linear3): Parameter containing: [torch.FloatTensor of size 4x2]
)
)
- 二维卷积层:使用
nn.Conv2d
类构造,模型参数包括卷积核和标量偏差,在训练模式时,通常先对卷积核随机初始化,再不断迭代卷积核和偏差
# 计算卷积层,对输入和输出做相应的升维和降维
def comp_conv2d(conv2d, X):
# (1, 1)代表批量大小和通道数
X = X.view((1, 1) + X.shape)
Y = conv2d(X)
# 排除不关心的前两维:批量和通道
return Y.view(Y.shape[2:])
# 注意这里是两侧分别填充1?或列,所以在两侧一共填充2?或列
conv2d = nn.Conv2d(in_channels=1, out_channels=1, kernel_size=3,padding=1)X = torch.rand(8, 8)
comp_conv2d(conv2d, X).shape
torch.Size([8, 8])
- 池化层:直接计算池化窗口内元素的最大值或者平均值,分别叫做最大池化或平均池化
# 二维池化层
def pool2d(X, pool_size, mode='max'):
p_h, p_w = pool_size
Y = torch.zeros((X.shape[0] - p_h + 1, X.shape[1] - p_w + 1))
for i in range(Y.shape[0]):
for j in range(Y.shape[1]):
if mode == 'max':
Y[i, j] = X[i: i + p_h, j: j + p_w].max()
elif mode == 'avg':
Y[i, j] = X[i: i + p_h, j: j + p_w].mean()
return Y
X = torch.tensor([[0, 1, 2], [3, 4, 5], [6, 7, 8]], dtype=torch.float)
pool2d(X, (2, 2), 'max')
tensor([[4., 5.],
[7., 8.]])
pool2d(X, (2, 2), 'avg')
tensor([[2., 3.],
[5., 6.]])
4.3 模型示例
- 神经网络训练过程:
- 定义可学习参数的神经网络
- 在输入数据集上进行迭代训练
- 通过神经网络处理输入数据
- 计算loss(损失值)
- 将梯度反向传播给神经网络参数
- 更新网络参数,使用梯度下降
- LeNet(前馈神经网络)
文章图片
?
import torch.nn.functional as Fclass Net(nn.Module):
def __init__(self):
super(Net, self).__init__()
# 输入图像channel是1;输出channel是6;5x5卷积核
self.conv1 = nn.Conv2d(1, 6, 5)
self.conv2 = nn.Conv2d(6, 16, 5)
# an affine operation: y = Wx + b
self.fc1 = nn.Linear(16 * 5 * 5, 120)
self.fc2 = nn.Linear(120, 84)
self.fc3 = nn.Linear(84, 10)def forward(self, x):
# 2x2 Max pooling
x = F.max_pool2d(F.relu(self.conv1(x)), (2, 2))
# 如果是方阵,则可以只使用一个数字进行定义
x = F.max_pool2d(F.relu(self.conv2(x)), 2)
x = x.view(-1, self.num_flat_features(x))
x = F.relu(self.fc1(x))
x = F.relu(self.fc2(x))
x = self.fc3(x)
return xdef num_flat_features(self, x):
# 除去批处理维度的其他所有维度
size = x.size()[1:]
num_features = 1
for s in size:
num_features *= s
return num_featuresnet = Net()
net
Net(
(conv1): Conv2d(1, 6, kernel_size=(5, 5), stride=(1, 1))
(conv2): Conv2d(6, 16, kernel_size=(5, 5), stride=(1, 1))
(fc1): Linear(in_features=400, out_features=120, bias=True)
(fc2): Linear(in_features=120, out_features=84, bias=True)
(fc3): Linear(in_features=84, out_features=10, bias=True)
)
# 假设输入的数据为随机的32x32
input = torch.randn(1, 1, 32, 32)
out = net(input)
print(out)
tensor([[-0.0921, -0.0605, -0.0726, -0.0451,0.1399, -0.0087,0.1075,0.0799,
-0.1472,0.0288]], grad_fn=)
# 清零所有参数的梯度缓存,然后进行随机梯度的反向传播
net.zero_grad()
out.backward(torch.randn(1, 10))
- AlexNet
class AlexNet(nn.Module):
def __init__(self):
super(AlexNet, self).__init__()
self.conv = nn.Sequential(
# in_channels, out_channels, kernel_size, stride, padding
nn.Conv2d(1, 96, 11, 4),
nn.ReLU(),
# kernel_size, stride
nn.MaxPool2d(3, 2),
# 减小卷积窗口,使用填充为2来使得输入与输出的高和宽一致,且增大输出通道数
nn.Conv2d(96, 256, 5, 1, 2),
nn.ReLU(),
nn.MaxPool2d(3, 2),
# 连续3个卷积层,且使用更小的卷积窗口。
# 除了最后的卷积层外,进一步增大了输出通道数。
# 前两个卷积层后不使用池化层来减小输入的高和宽
nn.Conv2d(256, 384, 3, 1, 1),
nn.ReLU(),
nn.Conv2d(384, 384, 3, 1, 1),
nn.ReLU(),
nn.Conv2d(384, 256, 3, 1, 1),
nn.ReLU(),
nn.MaxPool2d(3, 2)
)
# 这里全连接层的输出个数比LeNet中的大数倍。使用丢弃层来缓解过拟合
self.fc = nn.Sequential(
nn.Linear(256*5*5, 4096),
nn.ReLU(),
nn.Dropout(0.5),
nn.Linear(4096, 4096),
nn.ReLU(),
nn.Dropout(0.5),
# 输出层。由于这里使用Fashion-MNIST,所以用类别数为10,而非论文中的1000
nn.Linear(4096, 10),
)def forward(self, img):
feature = self.conv(img)
output = self.fc(feature.view(img.shape[0], -1))
return output
net = AlexNet()
print(net)
AlexNet(
(conv): Sequential(
(0): Conv2d(1, 96, kernel_size=(11, 11), stride=(4, 4))
(1): ReLU()
(2): MaxPool2d(kernel_size=3, stride=2, padding=0, dilation=1, ceil_mode=False)
(3): Conv2d(96, 256, kernel_size=(5, 5), stride=(1, 1), padding=(2, 2))
(4): ReLU()
(5): MaxPool2d(kernel_size=3, stride=2, padding=0, dilation=1, ceil_mode=False)
(6): Conv2d(256, 384, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
(7): ReLU()
(8): Conv2d(384, 384, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
(9): ReLU()
(10): Conv2d(384, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
(11): ReLU()
(12): MaxPool2d(kernel_size=3, stride=2, padding=0, dilation=1, ceil_mode=False)
)
(fc): Sequential(
(0): Linear(in_features=6400, out_features=4096, bias=True)
(1): ReLU()
(2): Dropout(p=0.5, inplace=False)
(3): Linear(in_features=4096, out_features=4096, bias=True)
(4): ReLU()
(5): Dropout(p=0.5, inplace=False)
(6): Linear(in_features=4096, out_features=10, bias=True)
)
)
5 损失函数
- 二分类交叉熵损失函数:
torch.nn.BCELoss
,用于计算二分类任务时的交叉熵
m = nn.Sigmoid()
loss = nn.BCELoss()
input = torch.randn(3, requires_grad=True)
target = torch.empty(3).random_(2)output = loss(m(input), target)
output.backward()
print('BCE损失函数的计算结果:',output)
BCE损失函数的计算结果: tensor(0.9389, grad_fn=)
- 交叉熵损失函数:
torch.nn.CrossEntropyLoss
,用于计算交叉熵
loss = nn.CrossEntropyLoss()
input = torch.randn(3, 5, requires_grad=True)
target = torch.empty(3, dtype=torch.long).random_(5)output = loss(input, target)
output.backward()
print('CrossEntropy损失函数的计算结果:',output)
CrossEntropy损失函数的计算结果: tensor(2.7367, grad_fn=)
- L1损失函数:
torch.nn.L1Loss
,用于计算输出y
和真实值target
之差的绝对值
loss = nn.L1Loss()
input = torch.randn(3, 5, requires_grad=True)
target = torch.randn(3, 5)output = loss(input, target)
output.backward()
print('L1损失函数的计算结果:',output)
L1损失函数的计算结果: tensor(1.0351, grad_fn=)
- MSE损失函数:
torch.nn.MSELoss
,用于计算输出y
和真实值target
之差的平方
loss = nn.MSELoss()
input = torch.randn(3, 5, requires_grad=True)
target = torch.randn(3, 5)output = loss(input, target)
output.backward()
print('MSE损失函数的计算结果:',output)
MSE损失函数的计算结果: tensor(1.7612, grad_fn=)
- 平滑L1(Smooth L1)损失函数:
torch.nn.SmoothL1Loss
,用于计算L1的平滑输出,减轻离群点带来的影响,通过与L1损失的比较,在0点的尖端处,过渡更为平滑
loss = nn.SmoothL1Loss()
input = torch.randn(3, 5, requires_grad=True)
target = torch.randn(3, 5)output = loss(input, target)
output.backward()
print('Smooth L1损失函数的计算结果:',output)
Smooth L1损失函数的计算结果: tensor(0.7252, grad_fn=)
- 目标泊松分布的负对数似然损失:
torch.nn.PoissonNLLLoss
loss = nn.PoissonNLLLoss()
log_input = torch.randn(5, 2, requires_grad=True)
target = torch.randn(5, 2)output = loss(log_input, target)
output.backward()
print('PoissonNL损失函数的计算结果:',output)
PoissonNL损失函数的计算结果: tensor(1.7593, grad_fn=)
- KL散度:
torch.nn.KLDivLoss
,用于连续分布的距离度量,可用在对离散采用的连续输出空间分布的回归场景
inputs = torch.tensor([[0.5, 0.3, 0.2], [0.2, 0.3, 0.5]])
target = torch.tensor([[0.9, 0.05, 0.05], [0.1, 0.7, 0.2]], dtype=torch.float)
loss = nn.KLDivLoss(reduction='batchmean')output = loss(inputs,target)
print('KLDiv损失函数的计算结果:',output)
KLDiv损失函数的计算结果: tensor(-1.0006)
- MarginRankingLoss:
torch.nn.MarginRankingLoss
,用于计算两组数据之间的差异(相似度),可使用在排序任务的场景
loss = nn.MarginRankingLoss()
input1 = torch.randn(3, requires_grad=True)
input2 = torch.randn(3, requires_grad=True)
target = torch.randn(3).sign()output = loss(input1, input2, target)
output.backward()
print('MarginRanking损失函数的计算结果:',output)
MarginRanking损失函数的计算结果: tensor(1.1762, grad_fn=)
- 多标签边界损失函数:
torch.nn.MultiLabelMarginLoss
,用于计算多标签分类问题的损失
loss = nn.MultiLabelMarginLoss()
x = torch.FloatTensor([[0.9, 0.2, 0.4, 0.8]])
# 真实的分类是,第3类和第0类
y = torch.LongTensor([[3, 0, -1, 1]])output = loss(x, y)
print('MultiLabelMargin损失函数的计算结果:',output)
MultiLabelMargin损失函数的计算结果: tensor(0.4500)
- 二分类损失函数:
torch.nn.SoftMarginLoss
,用于计算二分类的logistic
损失
# 定义两个样本,两个神经元
inputs = torch.tensor([[0.3, 0.7], [0.5, 0.5]])
target = torch.tensor([[-1, 1], [1, -1]], dtype=torch.float)# 该loss对每个神经元计算,需要为每个神经元单独设置标签
loss_f = nn.SoftMarginLoss()
output = loss_f(inputs, target)
print('SoftMargin损失函数的计算结果:',output)
SoftMargin损失函数的计算结果: tensor(0.6764)
- 多分类的折页损失函数:
torch.nn.MultiMarginLoss
,用于计算多分类问题的折页损失
inputs = torch.tensor([[0.3, 0.7], [0.5, 0.5]])
target = torch.tensor([0, 1], dtype=torch.long) loss_f = nn.MultiMarginLoss()
output = loss_f(inputs, target)
print('MultiMargin损失函数的计算结果:',output)
MultiMargin损失函数的计算结果: tensor(0.6000)
- 三元组损失函数:
torch.nn.TripletMarginLoss
,用于处理<实体1,关系,实体2>类型的数据,计算该类型数据的损失
triplet_loss = nn.TripletMarginLoss(margin=1.0, p=2)
anchor = torch.randn(100, 128, requires_grad=True)
positive = torch.randn(100, 128, requires_grad=True)
negative = torch.randn(100, 128, requires_grad=True)output = triplet_loss(anchor, positive, negative)
output.backward()
print('TripletMargin损失函数的计算结果:',output)
TripletMargin损失函数的计算结果: tensor(1.1507, grad_fn=)
- HingEmbeddingLoss:
torch.nn.HingeEmbeddingLoss
,用于计算输出的embedding结果的Hing损失
loss_f = nn.HingeEmbeddingLoss()
inputs = torch.tensor([[1., 0.8, 0.5]])
target = torch.tensor([[1, 1, -1]])output = loss_f(inputs,target)
print('HingEmbedding损失函数的计算结果:',output)
HingEmbedding损失函数的计算结果: tensor(0.7667)
- 余弦相似度:
torch.nn.CosineEmbeddingLoss
,用于计算两个向量的余弦相似度,如果两个向量距离近,则损失函数值小,反之亦然
loss_f = nn.CosineEmbeddingLoss()
inputs_1 = torch.tensor([[0.3, 0.5, 0.7], [0.3, 0.5, 0.7]])
inputs_2 = torch.tensor([[0.1, 0.3, 0.5], [0.1, 0.3, 0.5]])
target = torch.tensor([1, -1], dtype=torch.float)output = loss_f(inputs_1,inputs_2,target)
print('CosineEmbedding损失函数的计算结果:',output)
CosineEmbedding损失函数的计算结果: tensor(0.5000)
- CTC损失函数:
torch.nn.CTCLoss
,用于处理时序数据的分类问题,计算连续时间序列和目标序列之间的损失
# Target are to be padded
# 序列长度
T = 50
# 类别数(包括空类)
C = 20
# batch size
N = 16
# Target sequence length of longest target in batch (padding length)
S = 30
# Minimum target length, for demonstration purposes
S_min = 10input = torch.randn(T, N, C).log_softmax(2).detach().requires_grad_()
# 初始化target(0 = blank, 1:C = classes)
target = torch.randint(low=1, high=C, size=(N, S), dtype=torch.long)input_lengths = torch.full(size=(N,), fill_value=https://www.it610.com/article/T, dtype=torch.long)
target_lengths = torch.randint(low=S_min, high=S, size=(N,), dtype=torch.long)ctc_loss = nn.CTCLoss()
loss = ctc_loss(input, target, input_lengths, target_lengths)
loss.backward()
print('CTC损失函数的计算结果:',loss)
CTC损失函数的计算结果: tensor(6.1333, grad_fn=)
6 优化器 6.1 Optimizer的属性和方法
- 使用方向:为了使求解参数过程更快,使用BP+优化器逼近求解
- Optimizer的属性:
defaults
:优化器的超参数state
:参数的缓存param_groups
:参数组,顺序是params,lr,momentum,dampening,weight_decay,nesterov
- 【深度学习|PyTorch学习笔记(三)(PyTorch主要组成模块)】Optimizer的方法:
zero_grad()
:清空所管理参数的梯度step()
:执行一步梯度更新add_param_group()
:添加参数组load_state_dict()
:加载状态参数字典,可以用来进行模型的断点续训练,继续上次的参数进行训练state_dict()
:获取优化器当前状态信息字典
# 设置权重,服从正态分布--> 2 x 2
weight = torch.randn((2, 2), requires_grad=True)# 设置梯度为全1矩阵--> 2 x 2
weight.grad = torch.ones((2, 2))# 输出现有的weight和data
print("The data of weight before step:\n{}".format(weight.data))
print("The grad of weight before step:\n{}".format(weight.grad))
The data of weight before step:
tensor([[-0.5871, -1.1311],
[-1.0446,0.2656]])
The grad of weight before step:
tensor([[1., 1.],
[1., 1.]])
# 实例化优化器
optimizer = torch.optim.SGD([weight], lr=0.1, momentum=0.9)# 进行一步操作
optimizer.step()# 查看进行一步后的值,梯度
print("The data of weight after step:\n{}".format(weight.data))
print("The grad of weight after step:\n{}".format(weight.grad))
The data of weight after step:
tensor([[-0.6871, -1.2311],
[-1.1446,0.1656]])
The grad of weight after step:
tensor([[1., 1.],
[1., 1.]])
# 权重清零
optimizer.zero_grad()# 检验权重是否为0
print("The grad of weight after optimizer.zero_grad():\n{}".format(weight.grad))
The grad of weight after optimizer.zero_grad():
tensor([[0., 0.],
[0., 0.]])
# 添加参数:weight2
weight2 = torch.randn((3, 3), requires_grad=True)
optimizer.add_param_group({"params": weight2, 'lr': 0.0001, 'nesterov': True})# 查看现有的参数
print("optimizer.param_groups is\n{}".format(optimizer.param_groups))# 查看当前状态信息
opt_state_dict = optimizer.state_dict()
print("state_dict before step:\n", opt_state_dict)
optimizer.param_groups is
[{'params': [tensor([[-0.6871, -1.2311],
[-1.1446,0.1656]], requires_grad=True)], 'lr': 0.1, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0, 'nesterov': False}, {'params': [tensor([[ 0.0411, -0.6569,0.7445],
[-0.7056,1.1146, -0.4409],
[-0.2302, -1.1507, -1.3807]], requires_grad=True)], 'lr': 0.0001, 'nesterov': True, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0}]
state_dict before step:
{'state': {0: {'momentum_buffer': tensor([[1., 1.],
[1., 1.]])}}, 'param_groups': [{'lr': 0.1, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0, 'nesterov': False, 'params': [0]}, {'lr': 0.0001, 'nesterov': True, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0, 'params': [1]}]}
# 进行5次step操作
for _ in range(50):
optimizer.step()
# 输出现有状态信息
print("state_dict after step:\n", optimizer.state_dict())
state_dict after step:
{'state': {0: {'momentum_buffer': tensor([[0.0052, 0.0052],
[0.0052, 0.0052]])}}, 'param_groups': [{'lr': 0.1, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0, 'nesterov': False, 'params': [0]}, {'lr': 0.0001, 'nesterov': True, 'momentum': 0.9, 'dampening': 0, 'weight_decay': 0, 'params': [1]}]}
7 训练与评估
def train(epoch):
# 设置训练状态
model.train()
train_loss = 0
# 循环读取DataLoader中的全部数据
for data, label in train_loader:
# 将数据放到GPU用于后续计算
data, label = data.cuda(), label.cuda()
# 将优化器的梯度清0
optimizer.zero_grad()
# 将数据输入给模型
output = model(data)
# 设置损失函数
loss = criterion(label, output)
# 将loss反向传播给网络
loss.backward()
# 使用优化器更新模型参数
optimizer.step()
# 累加训练损失
train_loss += loss.item()*data.size(0)
train_loss = train_loss/len(train_loader.dataset)
print('Epoch: {} \tTraining Loss: {:.6f}'.format(epoch, train_loss))
def val(epoch):
# 设置验证状态
model.eval()
val_loss = 0
# 不设置梯度
with torch.no_grad():
for data, label in val_loader:
data, label = data.cuda(), label.cuda()
output = model(data)
preds = torch.argmax(output, 1)
loss = criterion(output, label)
val_loss += loss.item()*data.size(0)
# 计算准确率
running_accu += torch.sum(preds == label.data)
val_loss = val_loss/len(val_loader.dataset)
print('Epoch: {} \tTraining Loss: {:.6f}'.format(epoch, val_loss))
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