Introduction

We here present an application called with a single argument "n". This application returns the 'nth' prime number. The program is called through a REST api via an URL.

The computation of the Nth prime number is a very classical problem and many methods have already been proposed. Overall, these methods require either a high computational complexity or a large amount of RAM memory.

The program should run on an embedded device like a Raspberry Pi 3. To maintain a high efficiency of the service and reduce the computational cost, this code is based on a NoSQL database.

Platform

This code has been developped on Ubuntu 16.04 and does not depend on a specific version of Python.

Python requirements

Install required packages from requirements.txt

pip install -r requirements.txt

This will install the following packages

#cat requirements.txt
redis==2.10.6
web.py==0.38

For python3, you may have to install web.py using easy_install

:~$ easy_install web.py
:~$ pip install redis

Redis requirement

Install Redis client and server for your plateform from https://redis.io/.

A quickstart can be found in https://redis.io/topics/quickstart.

Redis may also be quickly installed by running the following commands.

wget http://download.redis.io/redis-stable.tar.gz
tar xvzf redis-stable.tar.gz
cd redis-stable
make
sudo make install

Package content

The current application contains 4 files:

requirements.txt : list of required python modules, to be ran with pip
primes.data : text file containing the 10M first prime numbers
fillup_redis.py : running the python script will laod 10M primes number in the Redis DB.
nth_prime_app.py : the main application will start a REST service available from your web browser.

All the files listed above must be placed the same directory.

How-To

In a Terminal, start the redis server. Keep this console open.

:~$ redis-server

In another terminal, check the connection to redis server by running:

:~$ redis-cli PING

This command should return PONG

Then install python dependencies

:~$ pip install -r requirements.txt

For python3, you may have to install web.py using easy_install

:~$ easy_install web.py
:~$ pip install redis

Unzip the file primes.data.gz

:~$ gunzip primes.data.gz

Then fill up the redis database by running

:~$ python fillup_redis.py

Filling up the redis database takes about 4 to 5 minutes depending on your system. You'll have to run this script only once.

Finally, you can launch the main app with

:~$ python nth_prime_app.py 8081

The service is now available from your web browser.

Connect to http://localhost:8081/nth_primes/n and set n to the value of nth prime number you want to return.

Example: http://localhost:8081/nth_primes/10000000 returns 179424673