Why is == faster than eql?

Question

I read in the documentation for the String class that eql? is a strict equality operator, without type conversion, and == is a equality operator wh

Answer 1

When doing benchmarks, don't use times, because that creates a closure RUN_COUNT times. The extra time taken as a result affects all benchmarks equally in absolute terms, but that makes it harder to notice a relative difference:

require "benchmark"

RUN_COUNT = 10_000_000
FIRST_STRING = "Woooooha"
SECOND_STRING = "Woooooha"

def times_eq_question_mark
  RUN_COUNT.times do |i|
    FIRST_STRING.eql?(SECOND_STRING)
  end
end

def times_double_equal_sign
  RUN_COUNT.times do |i|
    FIRST_STRING == SECOND_STRING
  end
end

def loop_eq_question_mark
  i = 0
  while i < RUN_COUNT
    FIRST_STRING.eql?(SECOND_STRING)
    i += 1
  end
end

def loop_double_equal_sign
  i = 0
  while i < RUN_COUNT
    FIRST_STRING == SECOND_STRING
    i += 1
  end
end

1.upto(10) do |i|
  method_names = [:times_eq_question_mark, :times_double_equal_sign, :loop_eq_question_mark, :loop_double_equal_sign]
  method_times = method_names.map {|method_name| Benchmark.measure { send(method_name) } }
  puts "Run #{i}"
  method_names.zip(method_times).each do |method_name, method_time|
    puts [method_name, method_time].join("\t")
  end
  puts
end

gives

Run 1
times_eq_question_mark    3.500000   0.000000   3.500000 (  3.578011)
times_double_equal_sign   2.390000   0.000000   2.390000 (  2.453046)
loop_eq_question_mark     3.110000   0.000000   3.110000 (  3.140525)
loop_double_equal_sign    2.109000   0.000000   2.109000 (  2.124932)

Run 2
times_eq_question_mark    3.531000   0.000000   3.531000 (  3.562386)
times_double_equal_sign   2.469000   0.000000   2.469000 (  2.484295)
loop_eq_question_mark     3.063000   0.000000   3.063000 (  3.109276)
loop_double_equal_sign    2.109000   0.000000   2.109000 (  2.140556)

Run 3
times_eq_question_mark    3.547000   0.000000   3.547000 (  3.593635)
times_double_equal_sign   2.437000   0.000000   2.437000 (  2.453047)
loop_eq_question_mark     3.063000   0.000000   3.063000 (  3.109275)
loop_double_equal_sign    2.140000   0.000000   2.140000 (  2.140557)

Run 4
times_eq_question_mark    3.547000   0.000000   3.547000 (  3.578011)
times_double_equal_sign   2.422000   0.000000   2.422000 (  2.437422)
loop_eq_question_mark     3.094000   0.000000   3.094000 (  3.140524)
loop_double_equal_sign    2.140000   0.000000   2.140000 (  2.140557)

Run 5
times_eq_question_mark    3.578000   0.000000   3.578000 (  3.671758)
times_double_equal_sign   2.406000   0.000000   2.406000 (  2.468671)
loop_eq_question_mark     3.110000   0.000000   3.110000 (  3.156149)
loop_double_equal_sign    2.109000   0.000000   2.109000 (  2.156181)

Run 6
times_eq_question_mark    3.562000   0.000000   3.562000 (  3.562386)
times_double_equal_sign   2.407000   0.000000   2.407000 (  2.468671)
loop_eq_question_mark     3.109000   0.000000   3.109000 (  3.124900)
loop_double_equal_sign    2.125000   0.000000   2.125000 (  2.234303)

Run 7
times_eq_question_mark    3.500000   0.000000   3.500000 (  3.546762)
times_double_equal_sign   2.453000   0.000000   2.453000 (  2.468671)
loop_eq_question_mark     3.031000   0.000000   3.031000 (  3.171773)
loop_double_equal_sign    2.157000   0.000000   2.157000 (  2.156181)

Run 8
times_eq_question_mark    3.468000   0.000000   3.468000 (  3.656133)
times_double_equal_sign   2.454000   0.000000   2.454000 (  2.484296)
loop_eq_question_mark     3.093000   0.000000   3.093000 (  3.249896)
loop_double_equal_sign    2.125000   0.000000   2.125000 (  2.140556)

Run 9
times_eq_question_mark    3.563000   0.000000   3.563000 (  3.593635)
times_double_equal_sign   2.453000   0.000000   2.453000 (  2.453047)
loop_eq_question_mark     3.125000   0.000000   3.125000 (  3.124900)
loop_double_equal_sign    2.141000   0.000000   2.141000 (  2.156181)

Run 10
times_eq_question_mark    3.515000   0.000000   3.515000 (  3.562386)
times_double_equal_sign   2.453000   0.000000   2.453000 (  2.453046)
loop_eq_question_mark     3.094000   0.000000   3.094000 (  3.140525)
loop_double_equal_sign    2.109000   0.000000   2.109000 (  2.156181)