def main():
# 3.7.1 获取和读取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_from_fashion_mnist(batch_size)
# 3.7.2 定义和初始化模型
num_inputs = 784
num_outputs = 10
class LinearNet(nn.Module):
def __init__(self, num_inputs, num_outputs):
super(LinearNet, self).__init__()
self.linear = nn.Linear(num_inputs, num_outputs)
def forward(self, x):
y = self.linear(x.view(x.shape[0], -1))
return y
net = LinearNet(num_inputs, num_outputs)
nn.init.normal_(net.linear.weight, mean=0, std=0.01)
nn.init.constant_(net.linear.bias, val=0)
# 3.7.3 softmax 和交叉熵损失函数
# PyTorch 提供了一个包括 softmax 和交叉熵损失计算的函数，它的数值稳定性更好
loss = nn.CrossEntropyLoss()
# 3.7.4 定义优化算法
optimizer = optim.SGD(net.parameters(), lr=0.1)
# 3.7.5 训练模型
num_epochs = 5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size,
None, None, optimizer)
def __manual():
# 获取和读取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
# 定义模型参数
num_inputs, num_outputs, num_hiddens = 784, 10, 256
W1 = torch.tensor(np.random.normal(0, 0.01, (num_inputs, num_hiddens)), dtype=torch.float)
b1 = torch.zeros(num_hiddens, dtype=torch.float)
W2 = torch.tensor(np.random.normal(0, 0.01, (num_hiddens, num_outputs)), dtype=torch.float)
b2 = torch.zeros(num_outputs, dtype=torch.float)
params = [W1, b1, W2, b2]
for param in params:
param.requires_grad_(requires_grad=True)
# 定义模型
def net(X):
X = X.view(-1, num_inputs)
H = relu(torch.matmul(X, W1) + b1)
return torch.matmul(H, W2) + b2
# 交叉熵损失函数
loss = torch.nn.CrossEntropyLoss()
# 训练模型
num_epochs, lr = 5, 100.0
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, params, lr)
def f1():
print("load_data_fashion_mnist start")
# 获取和读取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
print("load_data_fashion_mnist over")
num_inputs = 784
num_outputs = 10
# 定义和初始化模型
net = LinearNet(num_inputs, num_outputs)
net = nn.Sequential(
# FlattenLayer(),
# nn.Linear(num_inputs, num_outputs)
OrderedDict([('flatten', FlattenLayer()),
('linear', nn.Linear(num_inputs, num_outputs))]))
init.normal_(net.linear.weight, mean=0, std=0.01)
init.constant_(net.linear.bias, val=0)
loss = nn.CrossEntropyLoss()
# 定义优化算法
# 我们使用学习率为0.1的小批量随机梯度下降作为优化算法。
optimizer = torch.optim.SGD(net.parameters(), lr=0.1)
# 训练模型
# 接下来，我们使用上一节中定义的训练函数来训练模型。
num_epochs = 5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size,
None, None, optimizer)
def main():
# 3.6.1 获取和读取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_from_fashion_mnist(batch_size)
# 3.6.2 初始化模型参数
num_inputs = 784
num_outputs = 10
W = torch.tensor(np.random.normal(0, 0.01, (num_inputs, num_outputs)),
dtype=torch.float32)
b = torch.zeros(num_outputs, dtype=torch.float32)
W.requires_grad_(True)
b.requires_grad_(True)
# 3.6.3 实现 softmax 运算
def softmax(X):
X_exp = X.exp()
partition = X_exp.sum(dim=1, keepdim=True)
return X_exp / partition
# 3.6.4 定义模型
def net(X):
return softmax(torch.mm(X.view((-1, num_inputs)), W) + b)
# 3.6.5 定义损失函数
def cross_entropy(y_hat, y):
return -torch.log(y_hat.gather(1, y.view(-1, 1)))
# 3.6.6 计算分类准确率（已在 d2lzh 包中实现）
def accuracy(y_hat, y):
return (y_hat.argmax(dim=1) == y).float().mean().item()
# 3.6.7 训练模型
num_epochs, lr = 5, 0.1
d2l.train_ch3(net, train_iter, test_iter, cross_entropy, num_epochs,
batch_size, [W, b], lr)
# 3.6.8 预测
X, y = iter(test_iter).next()
true_labels = d2l.get_fashion_mnist_labels(y.numpy())
pred_labels = d2l.get_fashion_mnist_labels(net(X).argmax(dim=1).numpy())
titles = [
true + '\n' + pred for true, pred in zip(true_labels, pred_labels)
]
d2l.show_fashion_mnist(X[0:9], titles[0:9])
def __simplified():
num_inputs, num_outputs, num_hiddens = 784, 10, 256
net = nn.Sequential(
d2l.FlattenLayer(),
nn.Linear(num_inputs, num_hiddens),
nn.ReLU(),
nn.Linear(num_hiddens, num_outputs),
)
for params in net.parameters():
init.normal_(params, mean=0, std=0.01)
batch_size = 256
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
loss = torch.nn.CrossEntropyLoss()
optimizer = torch.optim.SGD(net.parameters(), lr=0.5)
# 训练模型
num_epochs = 5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, None, None, optimizer)
def main():
batch_size = 256
root = '../Datasets'
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size, root=root)
num_inputs = 784
num_outputs = 10
net = LinearNet(num_inputs, num_outputs)
net = nn.Sequential(
OrderedDict([('flatten', FlattenLayer()),
('linear', nn.Linear(num_inputs, num_outputs))]))
init.normal_(net.linear.weight, mean=0, std=0.01)
init.constant_(net.linear.bias, val=0)
loss = nn.CrossEntropyLoss()
optimizer = torch.optim.SGD(net.parameters(), lr=0.1)
num_epochs = 5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size,
None, None, optimizer)
def main():
# 3.9.1 获取和读取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_from_fashion_mnist(batch_size)
# 3.9.2 定义模型参数
num_inputs, num_outputs, num_hiddens = 784, 10, 256
W1 = torch.tensor(np.random.normal(0, 0.01, (num_inputs, num_hiddens)),
dtype=torch.float32)
b1 = torch.zeros(num_hiddens, dtype=torch.float32)
W2 = torch.tensor(np.random.normal(0, 0.01, (num_hiddens, num_outputs)),
dtype=torch.float32)
b2 = torch.zeros(num_outputs, dtype=torch.float32)
params = [W1, b1, W2, b2]
for param in params:
param.requires_grad_(True)
# 3.9.3 定义激活函数
def relu(X):
return torch.max(input=X, other=torch.tensor(0.0))
# 3.9.4 定义模型
def net(X):
X = X.view((-1, num_inputs))
H = relu(torch.mm(X, W1) + b1)
return torch.mm(H, W2) + b2
# 3.9.5 定义损失函数
loss = torch.nn.CrossEntropyLoss()
# 3.9.6 训练模型
num_epochs, lr = 5, 0.5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size,
params, lr)
def relu(X):
return torch.max(input=X, other=torch.tensor(0.0))
def net(X):
X = X.view((-1, num_inputs))
H = relu(torch.matmul(X, W1) + b1)
return torch.matmul(H, W2) + b2
loss = torch.nn.CrossEntropyLoss()
num_epochs, lr = 5, 100.0
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, params,
lr)
'''
3.10 多层感知机的简洁实现
https://tangshusen.me/Dive-into-DL-PyTorch/#/chapter03_DL-basics/3.10_mlp-pytorch
'''
import torch
from torch import nn
from torch.nn import init
import numpy as np
import sys
sys.path.append("..")
import d2lzh_pytorch as d2l
num_inputs, num_outputs, num_hiddens = 784, 10, 256
# 定义交叉熵损失函数
def cross_entropy(y_hat, y):
# -1 表示该维度大小由其他维度决定
# gather(dim, index) 可以理解为映射, index（即y）是一个tensor，它的dim和必须和y_hat一样
# 以y的值为下标，从y_hat中抽取对应的值
# 比如 torch.gather(t, 1, torch.tensor([[0,0],[1,0]])) 的结果为 tensor([[1, 1], [4, 3]])
return -torch.log(y_hat.gather(1, y.view(-1, 1))).sum() / y_hat.shape[0]
# 设置参数
batch_size, num_epochs, lr = 256, 3, 0.1
# 获取数据
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
# 训练模型
d2l.train_ch3(net, train_iter, test_iter, cross_entropy, num_epochs,
batch_size, [W, b], lr)
# 预测
X, y = iter(test_iter).next()
true_labels = d2l.get_fashion_mnist_labels(y.numpy())
pred_labels = d2l.get_fashion_mnist_labels(net(X).argmax(dim=1).numpy())
# 绘制
titles = [true + '\n' + pred for true, pred in zip(true_labels, pred_labels)]
for i in range(2):
# test[:] 记住冒号右边的下标的元素不会包含在目标列表中！
d2l.show_fashion_mnist(X[(5 * i):(5 * (i + 1))],
titles[(5 * i):(5 * (i + 1))])
def net(X, is_training=True):
X = X.view(-1, num_inputs)
H1 = (torch.matmul(X, W1) + b1).relu()
if is_training:
H1 = d2l.dropout(H1, drop_prob1) # 在第一层全连接后添加丢弃层（激活之后丢弃）
H2 = (torch.mm(H1, W2) + b2).relu()
if is_training:
H2 = d2l.dropout(H2, drop_prob2)
return torch.matmul(H2, W3) + b3
num_epochs, lr, batch_size = 4, 100.0, 256
loss = torch.nn.CrossEntropyLoss()
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
# 简洁版
net_pytorch = nn.Sequential(d2l.FlattenLayer(),
nn.Linear(num_inputs, num_hiddens1), nn.ReLU(),
nn.Dropout(drop_prob1),
nn.Linear(num_hiddens1, num_hiddens2), nn.ReLU(),
nn.Dropout(drop_prob2),
nn.Linear(num_hiddens2, num_outputs))
for p in params:
nn.init.normal_(p, mean=0, std=0.01)
# d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, params, lr)
optimizer = torch.optim.SGD(net_pytorch.parameters(), lr=0.5)
d2l.train_ch3(net_pytorch, train_iter, test_iter, loss, num_epochs, batch_size,
None, None, optimizer)
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
num_inputs, num_outputs = 784, 10
class FlattenLayer(nn.Module):
def __init__(self):
super(FlattenLayer, self).__init__()
def forward(self, x):
return x.view(x.shape[0], -1)
from collections import OrderedDict
net = nn.Sequential(
OrderedDict([('flattenlayer', FlattenLayer()),
('linear', nn.Linear(num_inputs, num_outputs))]))
init.normal_(net.linear.weight, mean=0, std=0.01)
init.constant_(net.linear.bias, val=0)
loss = nn.CrossEntropyLoss()
optimizer = torch.optim.SGD(net.parameters(), lr=0.1)
num_epochs = 5
d2l.train_ch3(net,
train_iter,
test_iter,
loss,
num_epochs,
batch_size,
optimizer=optimizer)
# 定义参数
num_inputs, num_outputs, num_hiddens = 784, 10, 256
# 定义网络
net = nn.Sequential(
d2l.FlattenLayer(),
nn.Linear(num_inputs, num_hiddens),
nn.ReLU(),
nn.Linear(num_hiddens, num_outputs),
)
# 初始化模型参数(但其实初始化网络时，参数已经初始化)
for params in net.parameters():
init.normal_(params, mean=0, std=0.01)
# 定义损失函数
loss = torch.nn.CrossEntropyLoss()
# 定义优化器
optimizer = torch.optim.SGD(net.parameters(), lr=0.5)
# 获取数据
batch_size = 256
train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)
# 训练模型
num_epochs = 5
d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, None,
None, optimizer) # lr已经包含在optimizer中
w1 = torch.tensor(np.random.normal(0, 0.01, (num_inputs, num_hiddens)), dtype=torch.float)
b1 = torch.zeros(num_hiddens, dtype=torch.float)
w2 = torch.tensor(np.random.normal(0, 0.01, (num_hiddens, num_outputs)), dtype=torch.float)
b2 = torch.zeros(num_outputs, dtype=torch.float)
params = [w1, b1, w2, b2]
for param in params:
param.requires_grad_(requires_grad=True)
def relu(x):
return torch.max(input=x, other=torch.tensor(0.0))
# 定义模型
def net(x):
x = x.view((-1, num_inputs))
h = relu(torch.matmul(x, w1) + b1)
return torch.matmul(h, w2) + b2
# 定义损失函数
loss = torch.nn.CrossEntropyLoss()
# 训练模型
num_epoch, lr = 5, 0.01
d2l.train_ch3(net, train_iter, test_iter, loss, num_epoch, batch_size, params, lr)