我也将以下内容发布到了Pytorch讨论板上。当向网络中添加更多神经元（到现有层，而不是新层）时，我试图保持每个参数的学习率。我编写了以下课程，让我可以在训练过程中将神经元添加到隐藏层中：
import torch
import torch.nn as nn
class DQN(nn.Module):
def __init__(self, num_inputs, hidden, num_actions, non_linearity):
super(DQN, self).__init__()
self.num_inputs = num_inputs
self.hidden = hidden
self.num_actions = num_actions
self.non_linearity = non_linearity
self.layers = nn.ModuleList()
self.layers.append(nn.Linear(num_inputs, self.hidden[0]))
previous = self.hidden[0]
for hidden_layer_size in self.hidden[1:]:
self.layers.append(nn.Linear(previous, hidden_layer_size))
previous = hidden_layer_size
self.layers.append(nn.Linear(previous, num_actions))
def forward(self, x):
for i in range(len(self.layers) - 1):
x = self.non_linearity(self.layers[i](x))
return self.layers[-1](x)
def increase_capacity(self, increment):
for i in range(len(self.hidden)):
self.hidden[i] += increment[i]
bias = self.layers[0].bias.data
weight = self.layers[0].weight.data
self.layers[0] = nn.Linear(self.num_inputs, self.hidden[0])
if increment[0]>0:
self.layers[0].weight.data[0:-increment[0],:] = weight
self.layers[0].bias.data[0:-increment[0]] = bias
else:
self.layers[0].weight.data[0:,:] = weight
self.layers[0].weight.data = bias
for i in range(1, len(self.layers) - 1):
bias = self.layers[i].bias.data
weight = self.layers[i].weight.data
self.layers[i] = nn.Linear(self.hidden[i-1], self.hidden[i])
if increment[i] > 0:
if increment[i-1] >0:
self.layers[i].bias.data[0:-increment[i]] = bias
self.layers[i].weight.data[0:-increment[i],0:-increment[i-1]] = weight
else:
self.layers[i].bias.data[0:-increment[i]] = bias
self.layers[i].weight.data[0:-increment[i],0:] = weight
else:
if increment[i-1] >0:
self.layers[i].bias.data = bias
self.layers[i].weight.data[0:,0:-increment[i-1]] = weight
else:
self.layers[i].bias.data = bias
self.layers[i].weight.data[0:,0:] = weight
bias = self.layers[-1].bias.data
weight = self.layers[-1].weight.data
self.layers[-1] = nn.Linear(self.hidden[-1], self.num_actions)
if increment[-1] >0:
self.layers[-1].bias.data = bias
self.layers[-1].weight.data[:,0:-increment[-1]] = weight
else:
self.layers[-1].bias.data = bias
self.layers[-1].weight.data[:,0:] = weight
def act(self, state, epsilon, mask):
if np.random.rand() > epsilon:
state = torch.tensor([state], dtype=torch.float32, device=device)
mask = torch.tensor([mask], dtype=torch.float32, device=device)
q_values = self.forward(state) + mask
action = q_values.max(1)[1].view(1, 1).item()
else:
action = np.random.randint(self.num_actions)
return action
现在，我已经写了一些健全性检查（在这一点上是否会导致健全性值得怀疑）：具有两个神经元和两个神经元的2层网络应该无法学习x或功能，而拥有4个神经元的网络已添加应该。如果我初始化一个新的优化器，这确实可以工作。我使用的优化器是Adam，它跟踪每个参数的学习率。在添加其他神经元之前，我想保持Adam的学习率和权重。以下是我这样做的失败尝试：
import random
import torch
import torch.nn as nn
import torch.optim as optim
import torch.nn.functional as F
import numpy as np
# Credits to Alvations
def generate_zero():
return random.uniform(0, 49) / 100
def generate_one():
return random.uniform(50, 100) / 100
def generate_xor_XY(num_data_points):
Xs, Ys = [], []
for _ in range(num_data_points):
# xor(0, 0) -> 0
Xs.append([generate_zero(), generate_zero()]); Ys.append([0])
# xor(1, 0) -> 1
Xs.append([generate_one(), generate_zero()]); Ys.append([1])
# xor(0, 1) -> 1
Xs.append([generate_zero(), generate_one()]); Ys.append([1])
# xor(1, 1) -> 0
Xs.append([generate_one(), generate_one()]); Ys.append([0])
return Xs, Ys
# Initialisation
network = DQN(2,[1,1],1,F.relu)
# optimizer = optim.Adam(network.parameters(), amsgrad=False)
optimizer = optim.Adam(network.parameters(), amsgrad=True)
criterion = nn.MSELoss()
# Train 50000 steps to show 1 neuron cannot solve x-or task
for i in range(50000):
optimizer.zero_grad()
Xs, Ys = generate_xor_XY(1)
Xs = torch.tensor(Xs)
Ys = torch.tensor(Ys, dtype=torch.float)
prediction = network(Xs)
loss = criterion(prediction, Ys)
loss.backward()
optimizer.step()
print(network(torch.tensor([[1,0],[0,1],[1,1],[0,0]], dtype=torch.float)))
print(loss)
# Add 5 neurons to first layer
capacity = [4,4]
network.increase_capacity(capacity)
# Uncomment the following line and comment the lines following it for normal initialisation.
# optimizer = optim.Adam(network.parameters(), amsgrad=True)
nw_param = [p for p in network.parameters()]
new_param_group = []
layer_idx = 0
for idx, group in enumerate(optimizer.param_groups):
for idx_p, p in enumerate(group['params']):
# Save previous information
prev_grad = p.grad
old_p = copy.deepcopy(p)
old_state = copy.copy(optimizer.state[p])
old_step = old_state['step']
old_exp_avg = old_state['exp_avg']
old_exp_avg_sq = old_state['exp_avg_sq']
old_max_exp_avg_sq = old_state['max_exp_avg_sq']
# Remove old parameter from state
optimizer.state.pop(p)
# Weights
if p.dim()>1:
p = nn.Parameter(nw_param[layer_idx])
p.grad = torch.zeros_like(p)
new_exp_avg = torch.torch.zeros_like(p)
new_exp_avg_sq = torch.torch.zeros_like(p)
new_max_exp_avg_sq = torch.torch.zeros_like(p)
p.grad[0:prev_grad.size(0),0:prev_grad.size(1)] = prev_grad
optimizer.state[p]['step'] = old_step
optimizer.state[p]['exp_avg'] = new_exp_avg
optimizer.state[p]['exp_avg'][0:prev_grad.size(0),0:prev_grad.size(1)] = old_exp_avg
optimizer.state[p]['exp_avg_sq'] = new_exp_avg_sq
optimizer.state[p]['exp_avg_sq'][0:prev_grad.size(0),0:prev_grad.size(1)] = old_exp_avg_sq
optimizer.state[p]['max_exp_avg_sq'] = new_max_exp_avg_sq
optimizer.state[p]['max_exp_avg_sq'][0:prev_grad.size(0),0:prev_grad.size(1)] = old_max_exp_avg_sq
new_param_group.append(p)
# Biases
else:
p = nn.Parameter(nw_param[layer_idx])
p.grad = torch.zeros_like(p)
new_exp_avg = torch.zeros_like(p)
new_exp_avg_sq = torch.zeros_like(p)
new_max_exp_avg_sq = torch.zeros_like(p)
p.grad[0:prev_grad.size(0)] = prev_grad
optimizer.state[p]['step'] = old_step
optimizer.state[p]['exp_avg'] = new_exp_avg
optimizer.state[p]['exp_avg'][0:prev_grad.size(0)] = old_exp_avg
optimizer.state[p]['exp_avg_sq'] = new_exp_avg_sq
optimizer.state[p]['exp_avg_sq'][0:prev_grad.size(0)] = old_exp_avg_sq
optimizer.state[p]['max_exp_avg_sq'] = new_max_exp_avg_sq
optimizer.state[p]['max_exp_avg_sq'][0:prev_grad.size(0)] = old_max_exp_avg_sq
new_param_group.append(p)
layer_idx += 1
optimizer.param_groups[0]['params'] = new_param_group
print(network)
# Train 50000 steps to show by adding neurons the task can be solved
for i in range(50000):
optimizer.zero_grad()
Xs, Ys = generate_xor_XY(1)
Xs = torch.tensor(Xs)
Ys = torch.tensor(Ys, dtype=torch.float)
prediction = network(Xs)
loss = criterion(prediction, Ys)
loss.backward()
optimizer.step()
print(network(torch.tensor([[1,0],[0,1],[1,1],[0,0]], dtype=torch.float)))
print(loss)
我正在尝试获得相同的优化器状态，但要为添加的神经元添加其他参数。这似乎是一种令人费解的方法（并且不起作用：p）。有谁知道这样做的简便方法，或者看看我要怎么做？