Relearning C++ : ++Basic Level

I am relearning C++ from the basics. It’s been 5 years when I first wrote my “Hello world” program in C, wasn’t a big fan of C++ back then because Python was more fun to code. Now that I am working at Nvidia, I have realized the importance of writing highly optimized code and how C++ really serves this purpose.

I believe having strong foundations in C++ is essential to make thyself a 10x programmer 😛

This is a journal to my learnings and findings of it or more like revision notes often copying information from the documentation and crediting the sources wherever necessary.

What kind of a programming language is C++?

  • Compiled language – One of the fastest languages in the world because it gets compiled to the machine language(0s and 1s) directly.
  • Strongly, static sometimes dynamic, unsafe type – Strongly typed because it requires explicit conversion to modify to another type, static because types are assigned to variables and not to run time objects, unsafe because it gives us more control with regards to type conversion.
  • Manifest and Inferred typing – Supports both explicitly defined variables and variables whose types need to be inferred.
  • Procedural, generic and Object-oriented – supports procedures and subroutines(functions), specifying types when algorithms are used, able to model objects like in real life.
  • Portable – runs on many platforms
  • Upward compatible with C – All C libraries can be run alongside C++
  • ISO-Standardized language

Structure of a c++ program

Not going into too many details here.

  • #include <iostream> is called a directive that a preprocessor interprets before the compilation of a program begins and includes the iostream header code.
  • using namespace std; some functions are part of the standard c++ code,

namespace – I have always ignored learning more about the namespace keyword, but they are very useful. Links provided helps to understand more about how it can be used. – article1, article2, article3

Variables and types

Variables are a portion of memory to store a value. Whenever a variable is defined in c++, the compiler allocates some memory to it based on the data type with which it is declared.

Identifiers: Contains letters, digits, or underscores. No Spaces, punctuation marks and symbols. Cannot start with digits, cannot match keywords and they are Case sensitive.

Data types: There are three kinds of data types in C++. Primitive, Derived and Abstract or User-defined data types.

2^8 = 256, 2^16 = 65,536, 2^32 ~ 4 billion(4 * 10^9), 2^64 ~ 18 billion billion (18 * 10^18)

Fundamental Data types: Built-in datatypes. These are.

  • Character types: char(1 byte), char16_t(>2 bytes), char32_t(>4 bytes), wchar_t(2 or 4 bytes)
  • Integer types:
    • Signed: signed char(>1 byte), signed short int(>2 bytes), signed int(>4 bytes), signed long int(>4 bytes(32bit machine), 8 bytes(64 bit machine)), signed long long int(> 8 bytes)
    • Unsigned: unsigned char, unsigned short int, unsigned int, unsigned long int, signed long long int (Sizes same as signed)
  • Floating-point types: float(4 bytes), double(8 bytes), long double(16 bytes)
  • Boolean type: bool(1 byte although only one bit is required)
  • Void type: void(no storage)
  • Null pointer: decltype(null)

Derived data types: Derived from fundamental datatypes. These are

  • Function: functionType functionName(parameters) Block of code that defines a well defined task.
  • Array/strings: Collection of items stored at continuous memory locations. Represent many instances in one variable. Dataype ArrayName[sizeofarray]
  • Pointers: symbolic representation of addresses. datatype* dataname
    int var = 20; // Value at var = 20
    int *ptr;
    ptr = &var; // Value at ptr = 0x777f7f(address), Value at ptr = 20
  • References: Alternative name for an existing variable datatype& dataname
    • int var1 = 10;
      int& var2 = var1; // var2 reference to var1
      var1 = 20; // Value of var2 = 20
      var2 = 25; // Value of var1 = 25

User defined datatypes: Class, structure, union, enumeration, typedef defined data type

Initialization of data types: Three ways

int x = 0;
int x (0); // via parantheses
int x {0}; // via curly braces

Type deduction: When a new variable is initialized, compiler can figure out what the type of variable is automatically by the intializer. Variables not initizalized can be declared by type deduction using decltype

int foo = 0;
auto bar = foo; // int bar
int foo1 = 0;
decltype(foo1) bar; // int bar





















Me @ GHCI’18


I am lucky to have the chance of attending GHCI’18 held at Bangalore India with my Outreachy travel fund.


The Grace Hopper Celebration India (GHCI) is the Asia’s largest gathering of women technologists, this year held on 14th, 15th and 16th of November at the Bangalore International Exhibition Center, Bangalore. It is produced by the AnitaB.Org in partnership with ACM India along with the leading sponsors like American Express, Google, Amazon, Microsoft, Adobe, Goldman Sachs, Oracle and the list continues….

GHCI offers technical and career development sessions like poster session, Career Fair, Women Entrepreneur Quest (WEQ), Tech Expo, Speed Mentoring and lots more. And, I am fortunate that I got the chance to be part of these sessions.

So GHCI is a three-day event.

Day-1 – keynote sessions

Day-2 – Microsoft reception, career fair, systers meet.

Day-3 – Mostly career fair


Systers at GHCI
Goodies from GHCI


First keynote speech was given by Lori Beer, the Global CIO of JPMorgan Chase & Co. She shared her story of her success and her struggles between family and work.

The Exciting Career Fair

The Career Fair was something that couldn’t be missed. A hall filled with company booths of the tech Giants, that a Technologist dreams off! It was a unique experience to visit the various booths interact with their representatives, learn new things and solve puzzles to win goodies!

I would like to thank Outreachy for providing me full fund to attend the conference.

I can’t thank enough for the important work Software Freedom Conservancy do for managing Outreachy funds and sending us our stipends smoothly.



Setting up ROUGE

ROUGE or Recall-Oriented Understudy for Gisting Evaluation is a set of metrics and a software package used for evaluating automatic summarization and machine translation software in natural language processing.The metrics compare an automatically produced summary or translation against a reference or a set of references (human-produced) summary or translation.

While working on my Project on Summarisation, in order to compare my generated summary against the reference summary I had to set up ROUGE. In contrast to how there’s a lot of content on every topic available on the internet, well, installing ROUGE only has a few articles. None of them provided the sequence of steps and the requirements to install it. I wished there was some blog written. The content was present but I had to piece it all together from multiple sources to set it up. But, let me make things easy for the future researchers here in this post.


1. Download ROUGE-1.5.5 from here You only need the ROUGE-1.5.5 directory.

git clone
cd pyrouge/tools/ROUGE-1.5.5

2. Check if Perl is installed else install it.

In Ubuntu, do

sudo apt-get install perl

3. For installing XML:DOM(this is a requirement for ROUGE to work) we install synaptic package manager

sudo apt-get update
sudo apt-get install synaptic

4. Once Synaptic Package manager is installed, search for Synaptic package manager in your applications and launch it.

Screenshot from 2018-08-04 21-29-44

Once the package manager is opened search “libxml-dom-perl” Screenshot from 2018-08-04 21-38-44

Click on Mark for Installation and apply changes.

Screenshot from 2018-08-04 22-20-37

5.  An environment variable ROUGE_EVAL_HOME must be set to point to the data directory.

export ROUGE_EVAL_HOME="/home/poojitha/pyrouge/tools/ROUGE-1.5.5/data/"

6. To avoid any WordNet exceptions, run these commands.

cd data/WordNet-2.0-Exceptions/
./ . exc WordNet-2.0.exc.db

cd ../
ln -s WordNet-2.0-Exceptions/WordNet-2.0.exc.db WordNet-2.0.exc.db

ROUGE is now installed, hurray!

Setting up pyrouge

pyrouge is a Python wrapper for the ROUGE summarization evaluation package. Getting ROUGE to work can require quite a bit of time. pyrouge is designed to make getting ROUGE scores easier by automatically converting your summaries into a format ROUGE understands, and automatically generating the ROUGE configuration file.

As of now, pypi version of pyrouge is deprecated, so let’s get the latest version from the repository

git clone
cd pyrouge

Set the ROUGE path with the command

pyrouge_set_rouge_path /home/poojitha/pyrouge/tools/ROUGE-1.5.5/

Command usage – pyrouge_set_rouge_path  /absolute/path/to/ROUGE-1.5.5/

Install pyrouge using

sudo python install

Test if everything’s installed by running


If the above command outputs “OK” , everything has been installed properly.





SSH Hacks

Jupyter Notebooks

The Jupyter Notebook App is a server-client application that allows editing and running notebook documents via a web browser.

You’re starting to experiment an unknown library and you write a big chunk of code, there are too many errors, so you start debugging but in the end you give up hope. Sad story, eh?

But what if you can write small chunks, check if it’s running fine and proceed to the next? That’d be so great. This is what Notebooks achieve and why I love it.

Remote port forwarding / Reverse ssh tunneling for jupyter notebooks

My laptop’s too slow to even run a hello world program and I try to run it on my friend’s powerful machine. I want to run not just any code, but a jupyter notebook.  This is how I do it.

I ssh into my friend’s machine first. Now, the

  • Current machine is my friend’s powerful machine – let it be C,
  • Remote machine is the local machine, my very slow laptop  – R

Start a jupyter notebook on C in a new session, using

jupyter-notebook --no-browser --port 8080

In another session on C, do this

ssh -N -f -R <portR>:localhost:<portC>  <user_name>@<local_machine_ip(R's ip)>

<portR> is R’s port we wish to use.

<portC> is C’s port that’s currently used, in this case it’s 8080

<user_name>@<local_machine_ip> is my slow laptop’s address.(R)

Now, I will be able to access the jupyter notebook on my laptop(R) and perform expensive operations using C’s resources.

Using bind address 

Syntax for the argument -R from the man pages of ssh

-R [bind_address:]port:host:hostport

My friend now wants to access my jupyter notebook on my machine and when I send the address <R's ip>:portR , my friend wouldn’t able to access it.

To allow nonlocal users to be able to connect R:portR through localhost:portC, follow these few steps.

R$ grep GatewayPorts /etc/ssh/sshd_config
#GatewayPorts no

In the R’s /etc/ssh/sshd_config file  add

GatewayPorts clientspecified

Restart sshd using

R$ sudo service sshd restart

and run in C,

ssh -N -f -R<portR>:localhost:<portC>  <user_name>@<local_machine_ip>


ssh -N -f -R \*:<portR>:localhost:<portC>  <user_name>@<local_machine_ip>


ssh -N -f -R "[::]:<portR>:localhost:<portC>"  <user_name>@<local_

If you do this very often, set up a special host in ~/.ssh/config on C:

 Host laptop
 HostName <R's ip>
 User <user_name>
 RemoteForward portR localhost:portC


  • -N  says that you want an SSH connection, but you don’t actually want to run any remote commands. If all you’re creating is a tunnel, then including this option saves resources.
  • -R  Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side.
  • -f  Requests ssh to go to background just before command execution



Some hacks

Share buttons

1. Sharing buttons – default.

&lt;script type="text/javascript" src=""> 
<p> Share on </p>
<span class='st_facebook_large' displayText='Facebook'></span>
<span class='st_twitter_large' displayText='Tweet'></span>
<span class='st_googleplus_large' displayText='Google +'></span>
<span class='st_linkedin_large' displayText='LinkedIn'></span>

2. Sharing custom text/image/url

Use properties like

st_url Specifies URL (can be shortened URL) that you would like shared
st_title Specifies title that you would like shared
st_image Specifies link to image you would like displayed in the shared content
st_summary Specifies summary text/description you wish to share

The above code would change into something like this,

&lt;script type="text/javascript" src=""></script>
<p> Share on </p>
<span class='st_facebook_large' displayText='Facebook'></span>
<span class='st_twitter_large' displayText='Tweet' st_title="This is custom text #Blog #tweet @systers_org"></span>
<span class='st_googleplus_large' displayText='Google +'></span>
<span class='st_linkedin_large' displayText='LinkedIn'></span>

3. Sharing custom text dynamically. (Django)

&lt;script type="text/javascript" src=""></script>
<p> Share on </p>
<span class='st_facebook_large' displayText='Facebook'></span>
<span class='st_twitter_large' displayText='Tweet' st_title="{{ share_message }}"></span>
<span class='st_googleplus_large' displayText='Google +'></span>
<span class='st_linkedin_large' displayText='LinkedIn'></span>

In the corresponding view add share message into the context, looks something like this.

def get_context_data(self, **kwargs):
     context = super(ExampleView, self).get_context_data(**kwargs)
     context['share_message'] = self.object.title " @systers_org " 
     return context


References : Custom Buttons

Journey with Systers so far…

It’s been a few weeks since I have started my internship, and there’s a lot to tell.

Community bonding period flew by quickly as I was having my end semester exams. Having finished my exams, and it being the start of my winter break, I had some free time before the official internship period begins.During that period, I was doubting myself if I could finish what I proposed and if I could make portal all set to serve the world. I wanted to get rid of all the anxiety and assert myself that I could do it, so I started the work a few days before the starting date. I was able to finish some tasks with less difficulty, Yay!

After that, I was eagerly waiting for the internship to begin so I can submit my first of many pull requests 😛 Working before official starting date made me less nervous and more confident about myself. Doubts washed away. Whoosh!

I did make a few resolutions on my first day. Some of them were – working sincerely throughout, writing code neater than what I usually code in my personal uni projects, write blogs, involve more with the community and learn more as the internship progresses.

Good Code


So, as an intern, I’d have to attend meetings. Meetings with May, mentors, fellow outreachy interns were so much fun. They weren’t what I thought they would be like, they’re so coool. There were meetings where we discussed the features on portal, setting up timeline – that was related to work, and there were meetings where it’s not always about work – there was a game we played that was to guess others tastes( to know more about my fellow outreachy interns), like talking about random stuff everyone’s interested in.

Coding is so much fun too, if only there were no errors XD. But, the truth is everyone’s bound to get errors, and get stuck once in a while. No matter how small the error can be and get stuck, it doesn’t mean that we’re stupid to not be able to solve it.

I didn’t know Django before, but, hey, now I do.  I knew I am good at python, MVC architectures, and MySQL, so I knew I would eventually be good at Django too. Most of the things I learned (listed under), I did know them(forms/views/migrations), it’s just that I’ve never ever coded them in Django. I’m a little confident in Django now, but not before I solved some of these tasks.


  1. The first task, Adding a  new community form for admin [1]  – I learned how to add a form, view, include context in it and a template, writing tests.
  2. Another task, Creating New community requests [1] – I can say I learned so much from this one task alone, that includes creating a model, understanding migrations, adding permissions and groups after understanding signals, creating a logic for approve feature, reject feature and sending messages using statuses of the task. One satisfying thing was that I was able to add all of them in a  week, although I put in a lot of effort into it in that week.
  3. Creating checkboxes, I was pondering over what model’s field type to add to it. Reddit’s r/Django helped me. I used the widget, was able to use checkboxes but I wasn’t able to store that in my dB, it took me quite some time to figure out what was happening. I created a new char field in the model, and a multiple-choice field with Checkboxselectmuliple widget in the model form for the same field and used a clean_field method to convert checkbox input into a char type.


As I was working, there were times when I was coding super fast, flawless, neat code, there were also times when every line I coded threw me errors and stack overflow seemed like a savior. It wasn’t always a rainbow. I did face a few errors which when googled were present in stack overflow, but none of them worked for me. I then tried to look at the errors for hours and days to analyze and make my own solution for it.  One such instance is this [1], I went on to use every answer present on the web (took me a lot of hours to do this), yet nothing solved it. I gave up looking for the answers online and came up with my own fix. But there were some errors that I just couldn’t fix even if I stare at it for days, and try out everything like this [1]

Fixing Problems

My Systers internship in Outreachy has been going on well, with ups and downs, with a lot to contribute, collaborate and lot to learn. I wish to do well in the remaining of my internship and make portal all set for production. I thank my mentors Tapasweni Pathak, Mansimar, and May for making my journey terrific so far.