prime-tester's Introduction

prime-tester

A Python program for doing things with prime numbers.

Launching the program grants you with a selection menu. Here, three options open to you :

Check if a number is prime
Display every prime number up to a given number
Benchmark your system with prime numbers

Prime checking

Checking if a number is prime is done efficiently by three functions:

isDivisibleByThree() checks the last digit of the number. If that digit is 0, 2, 4, 5, 6 or 8, then the number can't be prime because it can be at least divided by 2 or 5.
isDivisibleByThree() checks the digital root of the number (sum of all digits). If the digital root of a number is divisible by three, then the number is divisible by three. For example, digital root of 123 is 1+2+3=6, 6 is divisible by 3, so 123 is divisible by three. It's a modular arithmetic trick, I remember seeing a demonstration for it in math courses, I have to find it again.
isDivisibleByMoreThanSeven() searches for dividers equal or higher than 7. This function checks every non-previously tested number up to the square root of the number we are checking.

Benchmark

You are able to benchmark your system with primes numbers. The program searches for primes up to a given limit and records time taken by the operation.

Improvements to be made:

Algorithm has most likely room for improvements. It's already pretty optimized but I'm sure we can find primes faster ;)
Benchmark has to be adjusted to fit a real-world usecase. Calculating too few primes doesn't provide an accurate measure with modern computers, and calculating too many can take more time than the universe's age...
I would like to implement an option for choosing between single-threading and multi-threading. This program appears to take all threads by default. I have to learn how to handle threads, because it's now out of my reach.

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