Flutter HTTP host https://maven.google.com/ is not reachable in Windows 10

It shows the following error messages after executing flutter doctor in terminal prompt in Windows 10.

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.10.3, on Microsoft Windows [Version 10.0.19044.1586], locale zh-CN)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[√] Chrome - develop for the web
[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.11.2)
[√] Android Studio (version 4.1)
[√] Connected device (4 available)
[!] HTTP Host Availability
    X HTTP host https://maven.google.com/ is not reachable. Reason: An error occurred while checking the HTTP host:
      信号灯超时时间已到

    X HTTP host https://cloud.google.com/ is not reachable. Reason: An error occurred while checking the HTTP host:
      信号灯超时时间已到

How to handle HTTP host https://maven.google.com/ is not reachable?

1.Get the port of your http proxy

For example, my https proxy port is 10809, I get it in Option Settings in the v2 proxy. V2 socks port is 10808, https port is sock port +1 which is 10809;

nn_Module

1.Where are module parameters configured?

The parameters are stored in the network node which is one of points of a network layer. Neural network layer is defined in init method of module and need to be defined as class variable;

import torch.nn as nn
import numpy as np
class TorchDNN(nn.Module):

    def __init__(self, input, hidden, output):
        super(TorchDNN, self).__init__();
        layer_hidden = nn.Linear(input, hidden, bias = True);
    def forward(self, input_data):
        pass

x = np.array([1, 2, 3])
torch_model = TorchDNN(len(x), 5, 3)
print(torch_model.state_dict())
# OUTPUT:
# OrderedDict()

Network layer should be defined as a variable of Module class;

Github ssh key didn’t work

After you config a ssh key on github, you can test your ssh connection.

• 1.Open Terminal.
• 2.Enter the following:

$ ssh -T git@github.com

If you see your username of github in the resulting message, that means you configure successfully.

But, when you run git pull under the root of the project, the it prompt you to enter your Username of github, what is wrong?！

Now you should check that the URL in git config file starts with git@, instead of the http or https:

Understanding arange, unsqueeze, repeat, stack methods in Pytorch

• torch.arange(start=0, end, step=1) return 1-D tensor of size (end-start)/step which value begin from start and each value take with common differences step.

• torch.unsqueeze(input, dim) return a new tensor with a dimension of size one insterted at specified position; A dim value within the range [-input.dim() - 1, input.dim() + 1) can be used.

• tensor.repeat(size*) return a tensor; the new shape of tensor is that original shape multiplied by arguments correspondingly, if the number of paramter don’t match the original shape, then last dimension of new shape = the last dimension of original shape * last paramter;

Optimizer: L1 L2 Regularization

L1,L2 Loss function mean different type of loss function.

L1: sum(Y-f(x))     lasso
L2: sum(Y-f(x))^2   Ridge

L1, L2 regularization :

Y_predict = E(w_i(x_i)+b_i)

MES = E(Y-Y_predict)^2

L1: loss = MSE + 入E|w_i|
L2: loss = MES + 入E(w_i)^2

What does penalize the weights?

It means add another parameters to the loss function, so that the greater the weight, the higher the loss function value. That makes the weight parameters to be less or smaller.