模型搭建练习2_实现nn模块、optim、two_layer、dynamic_net
用variable实现nn.module
1 import torch 2 from torch.autograd import Variable 3 4 N, D_in, H, D_out = 64, 1000, 100, 10 5 6 x = Variable(torch.randn(N, D_in)) 7 y = Variable(torch.randn(N, D_out), requires_grad=False) 8 9 model = torch.nn.Sequential( 10 torch.nn.Linear(D_in, H), 11 torch.nn.ReLU(), 12 torch.nn.Linear(H, D_out), 13 ) 14 15 loss_fn = torch.nn.MSELoss(size_average=False) 16 17 learning_rate = 1e-4 18 for t in range(2): 19 # Forward pass 20 y_pred = model(x) 21 22 loss = loss_fn(y_pred, y) 23 # Zero the gradients before running the backward pass. 24 model.zero_grad() 25 # Backward pass: compute gradient of the loss with respect to all the learnable 26 # parameters of the model. Internally, the parameters of each Module are stored 27 # in Variables with requires_grad=True, so this call will compute gradients for 28 # all learnable parameters in the model. 29 loss.backward() 30 31 # Update the weights using gradient descent. Each parameter is a Variable 32 for param in model.parameters(): 33 param.data -= learning_rate * param.grad.data
实现optim
1 import torch 2 from torch.autograd import Variable 3 4 N, D_in, H, D_out = 64, 1000, 100, 10 5 x = Variable(torch.randn(N, D_in)) 6 y = Variable(torch.randn(N, D_out), requires_grad=False) 7 8 model = torch.nn.Sequential( 9 torch.nn.Linear(D_in, H), 10 torch.nn.ReLU(), 11 torch.nn.Linear(H, D_out), 12 ) 13 loss_fn = torch.nn.MSELoss(size_average=False) 14 15 learning_rate = 1e-4 16 # Use the optim package to define an Optimizer that will update the weights of 17 # the model for us. 18 optimizer = torch.optim.Adam(model.parameters(), lr=learning_rate) 19 for t in range(500): 20 # Forward pass: compute predicted y by passing x to the model. 21 y_pred = model(x) 22 loss = loss_fn(y_pred, y) 23 # Before the backward pass, use the optimizer object to zero all of the 24 # gradients for the variables it will update (which are the learnable weights 25 # of the model) 26 optimizer.zero_grad() 27 # Backward pass: compute gradient of the loss with respect to model 28 # parameters 29 loss.backward() 30 # Calling the step function on an Optimizer makes an update to its 31 # parameters 32 optimizer.step()
实现two_layer模型
1 import torch 2 from torch.autograd import Variable 3 4 class TwoLayerNet(torch.nn.Module): 5 def __init__(self, D_in, H, D_out): 6 super(TwoLayerNet, self).__init__() 7 self.linear1 = torch.nn.Linear(D_in, H) 8 self.linear2 = torch.nn.Linear(H, D_out) 9 10 def forward(self, x): 11 h_relu = self.linear1(x).clamp(min=0) 12 y_pred = self.linear2(h_relu) 13 return y_pred 14 15 N, D_in, H, D_out = 64, 1000, 100, 10 16 x = Variable(torch.randn(N, D_in)) 17 y = Variable(torch.randn(N, D_out), requires_grad=False) 18 19 model = TwoLayerNet(D_in, H, D_out) 20 criterion = torch.nn.MSELoss(size_average=False) 21 optimizer = torch.optim.SGD(model.parameters(), lr=1e-4) 22 for t in range(2): 23 y_pred = model(x) 24 loss = criterion(y_pred, y) 25 optimizer.zero_grad() 26 loss.backward() 27 optimizer.step()
实现dynamic_net
1 import random 2 import torch 3 from torch.autograd import Variable 4 5 class DynamicNet(torch.nn.Module): 6 def __init__(self, D_in, H, D_out): 7 super(DynamicNet, self).__init__() 8 self.input_linear = torch.nn.Linear(D_in, H) 9 self.middle_linear = torch.nn.Linear(H, H) 10 self.output_linear = torch.nn.Linear(H, D_out) 11 12 def forward(self, x): 13 h_relu = self.input_linear(x).clamp(min=0) 14 for _ in range(random.randint(0, 3)): 15 h_relu = self.middle_linear(h_relu).clamp(min=0) 16 y_pred = self.output_linear(h_relu) 17 return y_pred 18 19 N, D_in, H, D_out = 64, 1000, 100, 10 20 x = Variable(torch.randn(N, D_in)) 21 y = Variable(torch.randn(N, D_out), requires_grad=False) 22 model = DynamicNet(D_in, H, D_out) 23 24 criterion = torch.nn.MSELoss(size_average=False) 25 optimizer = torch.optim.SGD(model.parameters(), lr=1e-4, momentum=0.9) 26 for t in range(2): 27 y_pred = model(x) 28 loss = criterion(y_pred, y) 29 optimizer.zero_grad() 30 loss.backward() 31 optimizer.step()
