Quickly finding count of common elements in same length arrays in Ruby using RubyInline

benchmark_output

Calculating -------------------------------------
        ruby version       369 i/100ms
           c version      3413 i/100ms
-------------------------------------------------
        ruby version     3977.2 (±4.5%) i/s -      19926 in   5.020612s
           c version   450675.5 (±9.4%) i/s -    2221863 in   4.986029s
~/dev/theclymb$ ./bin/rails runner bench.rb 
Calculating -------------------------------------
        ruby version       360 i/100ms
           c version      3385 i/100ms
-------------------------------------------------
        ruby version     3923.5 (±4.9%) i/s -      19800 in   5.059191s
           c version   446588.8 (±9.7%) i/s -    2193480 in   4.968438s

common_element_count_bench.rb

require 'benchmark/ips'
require 'inline'

class Example
  inline do |builder|
    builder.c "
      static VALUE common_element_count(VALUE a1, VALUE a2) {
        int a_len = RARRAY_LEN(a1);
        int count = 0;
        int i = 0;

        VALUE *a1_arr = RARRAY_PTR(a1);
        VALUE *a2_arr = RARRAY_PTR(a2);

        for(i = 0; i < a_len; i++) {
          if (a1_arr[i] == a2_arr[i]) {
            count++;
          }
        }

        return INT2NUM(count);
      }"
  end

  def common_element_count_rb(a1, a2)
    count = 0

    i = 0
    len = a1.length
    while i < len
      count += 1 if a1[i] == a2[i]
      i += 1
    end

    count
  end
end

source_a = 10000.times.to_a
a1 = source_a.sample(5000)
a2 = source_a.sample(5000)
ex = Example.new

Benchmark.ips do |x|
  x.report('ruby version') do
    ex.common_element_count_rb(a1, a2)
  end

  x.report('c version') do
    ex.common_element_count(a1, a2)
  end
end