robertjlooby / primesieve-ruby

A wrapper for the primesieve C prime number generator

primesieve-ruby

Ruby bindings (gem wrapper) for the primesieve C++ library. Generates primes orders of magnitude faster than any pure Ruby code.

Installing

• Get primesieve

  • OS X: brew install primesieve
  • Build from source

• Get the primesieve gem

  • gem install primesieve -or-
  • add gem 'primesieve' to your Gemfile and run bundle install

Usage

The syntax of the primesieve Ruby bindings is nearly identical to the syntax of the primesieve C++ library.

require 'primesieve'

# Generate an array of the primes in (0..19)
Primesieve.generate_primes(0, 19) #=> [2, 3, 5, 7, 11, 13, 17, 19]

# Generate an array of the first 5 primes starting at 11
Primesieve.generate_n_primes(5, 11) #=> [11, 13, 17, 19, 23]

# Get the 10th prime
Primesieve.nth_prime(10, 0) #=> 29

# Get the 1st prime after 10**18
Primesieve.nth_prime(1, 10**18) #=> 1000000000000000003

# Get the number of primes below 10**10
Primesieve.count_primes(0, 10**10) #=> 4118054813

# Get the upper limit of primesieve
Primesieve.get_max_stop #=> 18446744073709551615

Here is a list of all available functions.

How fast is it?

Starting with version 6.0, primesieve uses all CPU cores by default.

Ruby 2.7.2 Prime module vs. primesieve to generate the first 10,000,000 primes:

           user     system      total        real
Ruby  15.015000   0.328000  15.343000 ( 15.350223)
gem    0.125000   0.032000   0.157000 (  0.157822)