## (MongoDB) How to use –fork On Windows for multiple servers

Although for most of developers, deploying database On Windows is not advised. For beginners like me, always need do some practise on Windows.

Currently I am studying replica sets, which asks me to run multiple servers at the same time with following commands.

# Logistic Regression with a Neural Network mindset

Welcome to your first (required) programming assignment! You will build a logistic regression classifier to recognize cats. This assignment will step you through how to do this with a Neural Network mindset, and so will also hone your intuitions about deep learning.
Continue reading “Logistic Regression with a Neural Network mindset”

## (Neural Network) Derivative of sigmoid function $f(z)=\frac{1}{1+e^{-z}}$ $f'(z)=f(z)(1-f(z))$

Process:

$$f(z)=\frac{1}{1+e^{-z}}$$
$$f'(z)=\frac{e^{-z}}{{(1+e^{-z}})^{2}}$$
$$=\frac{1+e^{-z}-1}{{(1+e^{-z}})^{2}}$$
$$=\frac{1}{(1+e^{-z}}) – \frac{1}{{(1+e^{-z}})^{2}}$$
$$=y(1 – y)$$

## JVM: Stack VS. Heap VS. Method Area Similar to Operating System, Java Virtual Machine offers a runtime data area. This time, I make a summery about stack, hep and method.

## Why we said JAVA is Pass by Value

Today, I was asked a question that Does Java pass by reference or pass by value?

A popular mistake is that when we pass primitives like int, char, etc. it pass by value, and when we pass objects, it pass by reference.

## NameError: name ‘urllib2’ is not defined

I am studying mongoDB with python, I met this problem.

When I tried to open a url by python, I copied some code from internet like following:

and met this error:
NameError: name urllib2 is not defined

Then I found that ‘urllib2’ is a lib for python2 while I use python3

Solution is easy by changing import lib

With this url, you can get two month free trial with a \$300 credit for one year.

## (crawler4j)SLF4J: Failed to load class “org.slf4j.impl.StaticLoggerBinder”.

While using crawler4j to crawl some data, I met errors as following:

Based on the official document I found solution:

https://www.slf4j.org/codes.html#StaticLoggerBinder

Then I downloadedlogback and import logback-classic.jar.

Perfect!

## Azure Function Error: The resource you are looking for has been removed, had its name changed, or is temporarily unavailable.

These days, I changed one of my Node.js Application from AWS to Azure. However, some functions do not work after migrating.