01_intersect_benchmark.rb

require "benchmark/ips"

A_SIZE_RANGE = 0..1000
B_SIZE_RANGE = 2..5
VAL_RANGE = 0...10000

def a
  Array.new(rand A_SIZE_RANGE) { rand VAL_RANGE }
end

def b
  Array.new(rand B_SIZE_RANGE) { rand VAL_RANGE }
end

Benchmark.ips do |x|
  x.report("(a&b).any?") { (a & b).any? }
  x.report("a.any? {|item| b.include?(item) }") { a.any? {|item| b.include?(item) } }
  x.compare!
end

02_out.txt

$ ruby -v
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin15]

$ ruby 01_intersect_benchmark.rb
Warming up --------------------------------------
                       (a&b).any?   839.000  i/100ms
b.any? {|item| a.include?(item) }   267.000  i/100ms
Calculating -------------------------------------
                       (a&b).any?   8.310k (± 6.4%) i/s -     41.950k in   5.073744s
b.any? {|item| a.include?(item) }   2.731k (± 5.2%) i/s -     13.617k in   5.000863s

Comparison:
                       (a&b).any?:  8310.2 i/s
b.any? {|item| a.include?(item) }:  2731.1 i/s - 3.04x  slower