我正在尝试更新/更改神经网络模型的参数,然后将更新后的神经网络的前向传递放在计算图中(无论我们做了多少更改/更新)。
我尝试了这个想法,但是每当我这样做时,pytorch 都会将我更新的张量(在模型内部)设置为叶子,这会阻止梯度流向我想要接收梯度的网络。它杀死了梯度流,因为叶节点不是我希望它们成为的计算图的一部分(因为它们不是真正的叶)。
我尝试了多种方法,但似乎没有任何效果。我创建了一个自包含的虚拟代码,它打印了我希望有渐变的网络的渐变:
import torch
import torch.nn as nn
import copy
from collections import OrderedDict
# img = torch.randn([8,3,32,32])
# targets = torch.LongTensor([1, 2, 0, 6, 2, 9, 4, 9])
# img = torch.randn([1,3,32,32])
# targets = torch.LongTensor([1])
x = torch.randn(1)
target = 12.0*x**2
criterion = nn.CrossEntropyLoss()
#loss_net = nn.Sequential(OrderedDict([('conv0',nn.Conv2d(in_channels=3,out_channels=10,kernel_size=32))]))
loss_net = nn.Sequential(OrderedDict([('fc0', nn.Linear(in_features=1,out_features=1))]))
hidden = torch.randn(size=(1,1),requires_grad=True)
updater_net = nn.Sequential(OrderedDict([('fc0',nn.Linear(in_features=1,out_features=1))]))
print(f'updater_net.fc0.weight.is_leaf = {updater_net.fc0.weight.is_leaf}')
#
nb_updates = 2
for i in range(nb_updates):
print(f'i = {i}')
new_params = copy.deepcopy( loss_net.state_dict() )
## w^<t> := f(w^<t-1>,delta^<t-1>)
for (name, w) in loss_net.named_parameters():
print(f'name = {name}')
print(w.size())
hidden = updater_net(hidden).view(1)
print(hidden.size())
#delta = ((hidden**2)*w/2)
delta = w + hidden
wt = w + delta
print(wt.size())
new_params[name] = wt
#del loss_net.fc0.weight
#setattr(loss_net.fc0, 'weight', nn.Parameter( wt ))
#setattr(loss_net.fc0, 'weight', wt)
#loss_net.fc0.weight = wt
#loss_net.fc0.weight = nn.Parameter( wt )
##
loss_net.load_state_dict(new_params)
#
print()
print(f'updater_net.fc0.weight.is_leaf = {updater_net.fc0.weight.is_leaf}')
outputs = loss_net(x)
loss_val = 0.5*(target - outputs)**2
loss_val.backward()
print()
print(f'-- params that dont matter if they have gradients --')
print(f'loss_net.grad = {loss_net.fc0.weight.grad}')
print('-- params we want to have gradients --')
print(f'hidden.grad = {hidden.grad}')
print(f'updater_net.fc0.weight.grad = {updater_net.fc0.weight.grad}')
print(f'updater_net.fc0.bias.grad = {updater_net.fc0.bias.grad}')
如果有人知道如何执行此操作,请给我一个 ping...我将要更新的次数设置为 2,因为更新操作应该在计算图中出现任意次数...所以它必须适用于2.
强相关帖子:
交叉发布:
最佳答案
不能正常工作,因为命名参数模块被删除。
似乎这有效:
import torch
import torch.nn as nn
from torchviz import make_dot
import copy
from collections import OrderedDict
# img = torch.randn([8,3,32,32])
# targets = torch.LongTensor([1, 2, 0, 6, 2, 9, 4, 9])
# img = torch.randn([1,3,32,32])
# targets = torch.LongTensor([1])
x = torch.randn(1)
target = 12.0*x**2
criterion = nn.CrossEntropyLoss()
#loss_net = nn.Sequential(OrderedDict([('conv0',nn.Conv2d(in_channels=3,out_channels=10,kernel_size=32))]))
loss_net = nn.Sequential(OrderedDict([('fc0', nn.Linear(in_features=1,out_features=1))]))
hidden = torch.randn(size=(1,1),requires_grad=True)
updater_net = nn.Sequential(OrderedDict([('fc0',nn.Linear(in_features=1,out_features=1))]))
print(f'updater_net.fc0.weight.is_leaf = {updater_net.fc0.weight.is_leaf}')
#
def del_attr(obj, names):
if len(names) == 1:
delattr(obj, names[0])
else:
del_attr(getattr(obj, names[0]), names[1:])
def set_attr(obj, names, val):
if len(names) == 1:
setattr(obj, names[0], val)
else:
set_attr(getattr(obj, names[0]), names[1:], val)
nb_updates = 2
for i in range(nb_updates):
print(f'i = {i}')
new_params = copy.deepcopy( loss_net.state_dict() )
## w^<t> := f(w^<t-1>,delta^<t-1>)
for (name, w) in list(loss_net.named_parameters()):
hidden = updater_net(hidden).view(1)
#delta = ((hidden**2)*w/2)
delta = w + hidden
wt = w + delta
del_attr(loss_net, name.split("."))
set_attr(loss_net, name.split("."), wt)
##
#
print()
print(f'updater_net.fc0.weight.is_leaf = {updater_net.fc0.weight.is_leaf}')
print(f'loss_net.fc0.weight.is_leaf = {loss_net.fc0.weight.is_leaf}')
outputs = loss_net(x)
loss_val = 0.5*(target - outputs)**2
loss_val.backward()
print()
print(f'-- params that dont matter if they have gradients --')
print(f'loss_net.grad = {loss_net.fc0.weight.grad}')
print('-- params we want to have gradients --')
print(f'hidden.grad = {hidden.grad}') # None because this is not a leaf, it is overriden in the for loop above.
print(f'updater_net.fc0.weight.grad = {updater_net.fc0.weight.grad}')
print(f'updater_net.fc0.bias.grad = {updater_net.fc0.bias.grad}')
make_dot(loss_val)
输出:
updater_net.fc0.weight.is_leaf = True
i = 0
i = 1
updater_net.fc0.weight.is_leaf = True
loss_net.fc0.weight.is_leaf = False
-- params that dont matter if they have gradients --
loss_net.grad = None
-- params we want to have gradients --
hidden.grad = None
updater_net.fc0.weight.grad = tensor([[0.7152]])
updater_net.fc0.bias.grad = tensor([-7.4249])
致谢:来自 pytorch 团队的强大 albanD:https://discuss.pytorch.org/t/how-does-one-have-the-parameters-of-a-model-not-be-leafs/70076/9?u=pinocchio
关于python - pytorch 模型中的参数如何不是叶子并且在计算图中?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60271131/