steps.cr

require "benchmark"

struct Foo
  def initialize(@size : Int32, @stride : Int32)
  end

  def step_from_class
    0.step(to: @size, by: @stride) do |i|
      yield i
    end
  end

  def step_from_explicit(n : Int32, step : Int32)
    0.step(to: n, by: step) do |i|
      yield i
    end
  end

  def times_explicit_single_step
    i = @size ^ @size
    while i < @size
      yield i
      i += 1
    end
  end

  def times_step_from_stride
    i = @size ^ @size
    while i < @size
      yield i
      i += @stride
    end
  end
end

n = 100_000
step = 1
f = Foo.new(n, step)

Benchmark.ips do |b|
  b.report("step from class") { f.step_from_class { |i| 2*i } }
  b.report("step_from_explicit_literal") { f.step_from_explicit(100_000, 1) { |i| 2*i } }
  b.report("step_from_explicit variable") { f.step_from_explicit(n, step) { |i| 2*i } }
  b.report("times explicit single step") { f.times_explicit_single_step { |i| 2*i } }
  b.report("times step from stride") { f.times_step_from_stride { |i| 2*i } }
end

#             step from class  20.62k ( 48.50µs) (± 6.12%)  0.0B/op   1.15× slower
#  step_from_explicit_literal  23.68k ( 42.24µs) (± 5.95%)  0.0B/op        fastest
# step_from_explicit variable  21.63k ( 46.24µs) (± 4.48%)  0.0B/op   1.09× slower
#  times explicit single step  21.54k ( 46.43µs) (± 4.84%)  0.0B/op   1.10× slower
#      times step from stride  22.30k ( 44.84µs) (± 1.26%)  0.0B/op   1.06× slower