DEV Community: Subhash Halder

Hello World Programming for Neural Networks: A Beginner's Guide to Getting Started.

Subhash Halder — Sun, 18 Jun 2023 12:34:21 +0000

Hello World

Many online introductions to neural networks tend to be technical or rely on frameworks. However, there's a simpler way to dive into the world of neural networks by implementing a basic "Hello World" program. In this article, we'll take you through a step-by-step process of building a straightforward neural network with just one neuron.

What is Artificial intelligence?

There are lots of definition of AI in web, but the simplest term how I think of AI is, it's a different paradigm of programming where we program a machine to attain a certain goal from a certain data.

So as in other paradigm of programming where we tell the computer step-by-step to achieve a certain goal, but in AI we don't tell the computer programming how to do a certain task, but we write the program that train the AI to do certain task.

It would become more clearer as we proceed through the basic "Hello World!" program.

Language we will use

To create the simplest neural network we will use JavaScript. I know JavaScript is not a performant language but for our simplest task it's fine, also most of programmer are familiar of JavaScript.

The problem

Our program is very simple let say you have been given a series of tuple where first element is the input and the second element is the desired output, now you have to write a program that can predict the output if you give any input other than the input provided.

const input = [
  [0, 0], [1, 2], [2, 4], [3, 6], [4, 8]
];

Since the input is very small so we can tell the answer will be y = x * 2, but it will be not easy to guess if you have millions of data. But from the data we can say the equation will be something like y = x * weight.

The Neuron

In our case we need a very simple neuron which will take one input and spits our one output, and to train the model we will use a Weight and a Bias.

Actual programming

So our Equation is y = x * w where w is the weight we need to find out.

// let take a random weight between 0 to 10
let weight = Math.random() * 10; // let say you got 5
// now let's pass the weight into the Equation, input is defined in above code snippet
const y = input[1][0] * weight; // y will be 5

Cost function

In the above code we are calculating the result of one input, but we have to do it for all input values to get the real difference.
We will create a cost function for this will will give the average distance from the real value.

function cost(weight) {
  result = 0;
  for (let i = 0; i < input.length; i++) {
    const x = input[i][0]; // actual input
    const y = input[i][1]; // actual output
    const calculatedResult = x * weight; // the result we have calculated from the weight
    const distance = calculatedResult - y; // the difference between the actual value and the calculated value
    result += distance * distance; // squaring the diff to remove negative and increase the difference so it is visible clearly
  }
  return result / input.length;
}

This cost function gives us idea how much we are away from the actual value so in order to get the correct result we need to reduce the cost function.
Now to minimise the cost function we can use derivative as it will give the direction for us to get the local minimum.

Derivative

The real derivative

It's very hard to implement so for now we will go with Finite difference which is The approximation of derivatives, central difference is the most used one.

Finite difference

Finite difference Wiki

equation for central difference is as follows

reducing the cost function

Now we can get the partial derivative of the cost function with respect to weight is as follows

const h = 0.001;
const dw = ((cost(wieght + h) - cost(weight - h)) / 2) * h;
weight -= dw; // this will adjust the weight to get to the local minimum.

Training

The training is very simple just loop through the reducing the cost function for certain no of time.

const iter = 1000; // we will adjust the weight 1000 time
learningRage = 0.001; // we need to have a learning rate to reduce the changes in the weight
for (let i = 0; i < iter; i++) {
  const dw = (cost(wieght + h) - cost(weight - h)) / (2 * h);
  weight -= learningRage * dw; // this will adjust the weight to get to the local minimum.
}

Final Code

const input = [
  [0, 0], [1, 2], [2, 4], [3, 6], [4, 8]
];

// let take a random weight between 0 to 10
let weight = Math.random() * 10;

function cost(weight) {
  result = 0;
  for (let i = 0; i < input.length; i++) {
    const x = input[i][0]; // actual input
    const y = input[i][1]; // actual output
    const calculatedResult = x * weight; // the result we have calculated from the weight
    const distance = calculatedResult - y; // the difference between the actual value and the calculated value
    result += distance * distance; // squaring the diff to remove negative and increase the difference so it is visible clearly
  }
  return result / input.length;
}

const h = 0.001;
const learningRage = 0.001;

const iter = 1000; // we will adjust the weight 1000 time

for (let i = 0; i < iter; i++) {
  const dw = (cost(weight + h) - cost(weight - h)) / (2 * h);
  weight -= learningRage * dw; // this will adjust the weight to get to the local minimum.

  console.log(`Weight: ${weight}, cost: ${cost(weight)}`);
}
console.log(`Final weight: ${weight}`);

For this input the Final weight would be closed to 2, also if you change the input the output will change accordingly.

How to Manage Multiple GitHub Repositories from a Single Machine

Subhash Halder — Sun, 18 Jun 2023 12:25:37 +0000

Problem

Many developers use their working laptop to contribute to open-source projects or personal projects. However, it can be a pain to set up a GitHub email for every repository. Sometimes we forget to update the email and contribute to a personal repository with our work email, or vice versa. Today I will show a simple solution to this problem.

Let say I am working in an Organization with GitHub username as subhash-xyz and my personal GitHub username is subhash-halder, first thing I do is set two different base folder for two username (you can use it for multiple account also).

# Organization projects base path
$ ~/Documents/work/xyz/
# Personal projects base path
$ ~/Documents/work/personal/

Create two different ssh keys

Now we need to create two different ssh keys for two different account.

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

This is the basic command to create ssh key, here we have to run the command two time and save the key in two different files. For more details of ssh key creation please visit this link.

I have created two ssh file as follows

$ ~/.ssh/github_xyz
$ ~/.ssh/github_personal

Now we have to add the public key to the respective GitHub Account.

Create a global .gitconfig

Now create a .gitconfig file in you home directory and paste the following code, please update it according to your need.

# ~/.gitconfig
[includeIf "gitdir:~/Documents/work/personal/"]
  path = ~/.gitconfig-personal
[includeIf "gitdir:~/Documents/work/xyz/"]
  path = ~/.gitconfig-xyz

This tells Git if the git folder is inside these folder use the respective config files.

Create the folder specific git configuration

Since we have specified that we will use different configuration file for different folder now we need to create them.

`~/.gitconfig-personal`

[user]
  name = Subhash Halder
  email = halder.subhash@gmail.com

[github]
  user = "subhash-halder"

[core]
  sshCommand = "ssh -i  ~/.ssh/personal_github"

`~/.gitconfig-xyz`

[user]
  name = Subhash Halder
  email = halder.subhash@xyz.com

[github]
  user = "subhash-xyz"

[core]
  sshCommand = "ssh -i  ~/.ssh/personal_xyz"

You can now use git command without worry

# If I run git clone command from personal folder it will use my personal ssh key
~/Documents/work/personal $ git clone git@github.com:subhash-halder/subhashhalder.com.git
~/Documents/work/personal $ cd subhashhalder.com
# If you run git command from inside the git folder it will show the config from the local configuration file.
~/Documents/work/personal/subhashhalder.com $ git config user.email
~/Documents/work/personal/subhashhalder.com $ halder.subhash@gmail.com
# If you run git command from inside the git folder of your Organization dir it will show the config from the local configuration file.
~/Documents/work/xyz $ git clone git@github.com:xyz/demo.git
~/Documents/work/xyz $ cd demo
~/Documents/work/xyz/demo $ git config user.email
~/Documents/work/xyz/demo $ halder.subhash@xyz.com

How to Stay on Top of Your Gmail Inbox with AppScript

Subhash Halder — Sun, 18 Jun 2023 12:21:21 +0000

Gmail is a powerful tool, but it can be difficult to keep your inbox organized. Apps Script is a scripting language like JavaScript that can help you automate tasks in Gmail, freeing up your time to focus on more important things.

What is Apps Script?

Google Apps Script is a cloud-based scripting platform that lets you integrate with and automate tasks across Google products. It's a powerful tool that can be used to automate tasks. It's based on JavaScript, so if you know JavaScript, you'll be able to pick it up quickly. And if you don't know JavaScript, there are plenty of resources available to help you learn.

Why not using Gmail filter?

Gmail filters are very effective for filtering and categorizing emails with simple terms like email patterns or simple regular expressions. However, they can be difficult to use when you need to filter for more complex patterns, such as if a pattern is only present in the subject line or if you are only mentioned in the email body.

Why I needed this process?

I was getting a lot of email notifications from GitHub, but most of them were from the build process and were not that important. The sheer number of these notifications made it difficult to see the important ones. So, I thought of creating a filter that would categorize GitHub emails into two categories github-important and github-not-important. So I created two labels with the name, now how do i categorize the email that I am getting in Inbox? I have tried with simple filter option but it doesn't work for every case.

How to write Apps Script?

To write google Apps Script you have to go the URL https://script.google.com/ and start writing the script. Give a name to the project so that you can search it easily afterword.

Lets start with the script

Here is a simple script that will print 10 email subject and every email in the thread from notifications@github.com.

function githubNotiCategorizer() {
  const query = `from:(notifications@github.com) label:inbox`;
  const emails = GmailApp.search(query, 0, 10);
  for(const email of emails) {
    const subject = email.getFirstMessageSubject();
    console.log("Message Subject", subject);
      const messages = email.getMessages();
      for (const message of messages) {
        const messageBody = message.getBody();
        console.log("Message Body: ", messageBody)
      }
    }
  }
}

Copy paste the above code in the editor of the script project, to run it select the function name in the toolbar drop down and click the run button, you will be able to see the logs of the email from GitHub notification (if any).

Next step

If you are able to run the code then you are few step away from organizing your GitHub notification.

Create two Gmail Label like github-important and github-not-important.
We need to modify the script to distribute the notification between two label and we will remove the inbox label so inbox doesn't contain these emails.
Schedule this code to run every 1 hour ( customizable as your need ).

Final Script

function githubNotiCategorizer() {
  const query = `from:(notifications@github.com) label:inbox`;
  const emails = GmailApp.search(query, 0, 10);
  const myNameRegex = /subhash/i; // will match if have my name.
  const subjectFilterRegex = /^((?!(run failed)).)*$/i; // will match if "run failed" is not available.
  for(const email of emails) {
    let isImportant = false;
    const subject = email.getFirstMessageSubject();
    if(subject.match(subjectFilterRegex)) {
      isImportant = true;
    }
    const messages = email.getMessages();
    for (const message of messages) {
      const messageBody = message.getBody();
      if(messageBody.match(myNameRegex)) {
        isImportant = true;
        break;
      }
    }
    if(isImportant) {
      email.addLabel(GmailApp.getUserLabelByName('github-important'));
      email.moveToArchive(); // remove the inbox label so it will not be shown in the inbox
    } else {
      email.addLabel(GmailApp.getUserLabelByName('github-not-important'));
      email.moveToArchive(); // remove the inbox label so it will not be shown in the inbox
    }
  }
}

Scheduler

Now you have a script that can categorize your GitHub notifications, but how can we schedule it so it can run on new messages. Google script has that feature also you can activate the scheduler to run this function every hour ( as frequent you needed ) with the following script. Running the script by selecting the function name from the dropdown and pressing the play button will create a trigger.

function setTrigger() {
  // This will run the **githubNotiCategorizer** every hour
  ScriptApp.newTrigger('githubNotiCategorizer').timeBased().everyHours(1).create();
}

I the left panel of the script editor there is a menu of trigger which will have all the trigger, you can see your trigger is registered over there.
You can manually create the trigger also without writing the above code.

Now you know how to do it, you can do all sorts of cool automation with app script. I will write more about app script later, please let me know in the comment if you have any cool idea.

Host Your Site Without Static IP via Server

Subhash Halder — Sun, 18 Jun 2023 12:19:19 +0000

Why you want to do that?

This would be the first question if I need a server for this why would I need to expose any service from local in first place?

One of the reason would be to reduce server cost, like say you want to do some graphic intensive task which you can do in your local.
You can share your local work with other without publishing your work and without using services like ngrok

Prerequisite

Basic understanding of SSH is required, also I have done it with a linux machine will be same for mac I don't know how this works with windows machine.

How to Do it?

Suppose you have a server running on port 8080 and want to expose it to the outside world but you don't have a public IP.
So to make it public you need to have a server with public IP running in cloud (or any where) and SSH running in both the mechine.
Let say the IP address of the public server is pp.pp.pp.pp
then in the private server run the command

ssh -NT -o ServerAliveInterval=5 -o ExitOnForwardFailure=yes -R 80:127.0.0.1:8080 ubuntu@pp.pp.pp.pp

or to run it through systemd use this systemd file inside /etc/systemd/system/api-tunnel.service

/etc/systemd/system/api-tunnel.service

[Unit]
Description=api server tunnel
After=network.target
StartLimitIntervalSec=0
[Service]
Type=simple
Restart=always
RestartSec=1
User=ubuntu
ExecStart=/usr/bin/env ssh -NT -o ServerAliveInterval=5 -o ExitOnForwardFailure=yes  -R 80:127.0.0.1:8080 ubuntu@pp.pp.pp.pp

[Install]
WantedBy=multi-user.target

after succesfully running the command if you go the url pp.pp.pp.pp from any browser you will see the website running in port 8080 in your private machine

also need to update the sshd config file for the server machine to reduce the latency if the tunnel disconnect

/etc/ssh/sshd_config

ClientAliveInterval 5
ClientAliveCountMax 3