接着上篇《PyTorch简明教程上篇》，继续学习多层感知机，卷积神经网络和LSTMNet。
1、多层感知机
多层感知机通过在网络中加入一个或多个隐藏层来克服线性模型的限制，是一个简单的神经网络，也是深度学习的重要基础，具体图如下：
import numpy as np
import torch
from torch.autograd import Variable
from torch import optim
from data_util import load_mnist
def build_model(input_dim, output_dim):
return torch.nn.Sequential(
torch.nn.Linear(input_dim, 512, bias=False),
torch.nn.ReLU(),
torch.nn.Dropout(0.2),
torch.nn.Linear(512, 512, bias=False),
torch.nn.ReLU(),
torch.nn.Dropout(0.2),
torch.nn.Linear(512, output_dim, bias=False),
)
def train(model, loss, optimizer, x_val, y_val):
model.train()
optimizer.zero_grad()
fx = model.forward(x_val)
output = loss.forward(fx, y_val)
output.backward()
optimizer.step()
return output.item()
def predict(model, x_val):
model.eval()
output = model.forward(x_val)
return output.data.numpy().argmax(axis=1)
def main():
torch.manual_seed(42)
trX, teX, trY, teY = load_mnist(notallow=False)
trX = torch.from_numpy(trX).float()
teX = torch.from_numpy(teX).float()
trY = torch.tensor(trY)
n_examples, n_features = trX.size()
n_classes = 10
model = build_model(n_features, n_classes)
loss = torch.nn.CrossEntropyLoss(reductinotallow='mean')
optimizer = optim.Adam(model.parameters())
batch_size = 100
for i in range(100):
cost = 0.
num_batches = n_examples // batch_size
for k in range(num_batches):
start, end = k * batch_size, (k + 1) * batch_size
cost += train(model, loss, optimizer,
trX[start:end], trY[start:end])
predY = predict(model, teX)
print("Epoch %d, cost = %f, acc = %.2f%%"
% (i + 1, cost / num_batches, 100. * np.mean(predY == teY)))
if __name__ == "__main__":
main()分享说明：转发分享请注明出处。
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