Pytorch实现mnist手写数字识别
2020/6/29
Hey,突然想起来之前做的一个入门实验,用pytorch实现mnist手写数字识别。可以在这个基础上增加网络层数,或是尝试用不同的数据集,去实现不一样的功能。
Mnist数据集如图:
代码如下:
- import torch
- import torch.nn as nn
- import torch.utils.data as Data
- import torchvision # 数据库模块
- import matplotlib.pyplot as plt
- torch.manual_seed(1) # reproducible
- # Hyper Parameters
- EPOCH = 1 # 训练整批数据多少次, 为了节约时间, 我们只训练一次
- BATCH_SIZE = 50
- LR = 0.001 # 学习率
- DOWNLOAD_MNIST = True # 如果你已经下载好了mnist数据就写上 False
- # Mnist 手写数字
- train_data = torchvision.datasets.MNIST(
- root='./mnist/', # 保存或者提取位置
- train=True, # this is training data
- transform=torchvision.transforms.ToTensor(), # 转换 PIL.Image or numpy.ndarray 成
- # torch.FloatTensor (C x H x W), 训练的时候 normalize 成 [0.0, 1.0] 区间
- download=DOWNLOAD_MNIST, # 没下载就下载, 下载了就不用再下了
- )
- test_data = torchvision.datasets.MNIST(root='./mnist/', train=False)
- # 批训练 50samples, 1 channel, 28x28 (50, 1, 28, 28)
- train_loader = Data.DataLoader(dataset=train_data, batch_size=BATCH_SIZE, shuffle=True)
- # 为了节约时间, 我们测试时只测试前2000个
- test_x = torch.unsqueeze(test_data.test_data, dim=1).type(torch.FloatTensor)[:2000]/255. # shape from (2000, 28, 28) to (2000, 1, 28, 28), value in range(0,1)
- test_y = test_data.test_labels[:2000]
- class CNN(nn.Module):
- def __init__(self):
- super(CNN, self).__init__()
- self.conv1 = nn.Sequential( # input shape (1, 28, 28)
- nn.Conv2d(
- in_channels=1, # input height
- out_channels=16, # n_filters
- kernel_size=5, # filter size
- stride=1, # filter movement/step
- padding=2, # 如果想要 con2d 出来的图片长宽没有变化, padding=(kernel_size-1)/2 当 stride=1
- ), # output shape (16, 28, 28)
- nn.ReLU(), # activation
- nn.MaxPool2d(kernel_size=2), # 在 2x2 空间里向下采样, output shape (16, 14, 14)
- )
- self.conv2 = nn.Sequential( # input shape (16, 14, 14)
- nn.Conv2d(16, 32, 5, 1, 2), # output shape (32, 14, 14)
- nn.ReLU(), # activation
- nn.MaxPool2d(2), # output shape (32, 7, 7)
- )
- self.out = nn.Linear(32 * 7 * 7, 10) # fully connected layer, output 10 classes
- def forward(self, x):
- x = self.conv1(x)
- x = self.conv2(x)
- x = x.view(x.size(0), -1) # 展平多维的卷积图成 (batch_size, 32 * 7 * 7)
- output = self.out(x)
- return output
- cnn = CNN()
- print(cnn) # net architecture
- """
- CNN (
- (conv1): Sequential (
- (0): Conv2d(1, 16, kernel_size=(5, 5), stride=(1, 1), padding=(2, 2))
- (1): ReLU ()
- (2): MaxPool2d (size=(2, 2), stride=(2, 2), dilation=(1, 1))
- )
- (conv2): Sequential (
- (0): Conv2d(16, 32, kernel_size=(5, 5), stride=(1, 1), padding=(2, 2))
- (1): ReLU ()
- (2): MaxPool2d (size=(2, 2), stride=(2, 2), dilation=(1, 1))
- )
- (out): Linear (1568 -> 10)
- )
- """
- optimizer = torch.optim.Adam(cnn.parameters(), lr=LR) # optimize all cnn parameters
- loss_func = nn.CrossEntropyLoss() # the target label is not one-hotted
- # training and testing
- for epoch in range(EPOCH):
- for step, (b_x, b_y) in enumerate(train_loader): # 分配 batch data, normalize x when iterate train_loader
- output = cnn(b_x) # cnn output
- loss = loss_func(output, b_y) # cross entropy loss
- optimizer.zero_grad() # clear gradients for this training step
- loss.backward() # backpropagation, compute gradients
- optimizer.step() # apply gradients
- """
- ...
- Epoch: 0 | train loss: 0.0306 | test accuracy: 0.97
- Epoch: 0 | train loss: 0.0147 | test accuracy: 0.98
- Epoch: 0 | train loss: 0.0427 | test accuracy: 0.98
- Epoch: 0 | train loss: 0.0078 | test accuracy: 0.98
- """
- test_output = cnn(test_x[:10])
- pred_y = torch.max(test_output, 1)[1].data.numpy().squeeze()
- print(pred_y, 'prediction number')
- print(test_y[:10].numpy(), 'real number')
- """
- [7 2 1 0 4 1 4 9 5 9] prediction number
- [7 2 1 0 4 1 4 9 5 9] real number
- """
这个项目还是很有意思,对于初学者可以先试着对32-60行进行修改,增加网络层数。看看最后效果如何。
九层之台,起于累土。那天看到一句话,一个人把自己的事情做好,已经很不容易了。现在回想起之前安安静静在实验室的日子感觉很遥远,这半年来总是有各种各样的烦心事儿,也少了很多可以静下心来安静学习的时间。也许这就是生活吧C'est La Vie。我们总是要迎接挑战的,虽然没法回学习但是在智星云组用的GPU也是一样的好用,环境都是配置好了的,用来做实验非常节省时间和精力。有同样需求的朋友可以参考:智星云官网: http://www.ai-galaxy.cn/,淘宝店:https://shop36573300.taobao.com/公众号: 智星AI,
最后再唠叨两句,明天就是6月的最后一天了,眼看着2020年就要过去一半了,岁月不居,时节如流。通过这次疫情也让我深刻的认识到管理好自己的时间是多么的重要。往者不可谏,来者犹可追。
PEACE
参考资料:
https://pytorch.org/docs/stable/index.html
https://morvanzhou.github.io/tutorials/machine-learning/torch/
http://www.planetb.ca/syntax-highlight-word
https://shop36573300.taobao.com/