Benchmark while vs each_with_index. And for vs map. RE: https://github.com/rails/rails/pull/12065

for_vs_map.rb

require 'benchmark/ips'

ARRAY = [1,2,3,1,'2',4,'5',6,7,8,9,'10']

Benchmark.ips do |x|
  x.report("for") {
    result = []
    for number in ARRAY
      result << number.to_s
    end
    result
  }

  x.report("map") {
    ARRAY.map do |number|
      number.to_s
    end
  }
end

while-vs-each_with_index.rb

require 'benchmark/ips'

ARRAY = [1,2,3,1,'2',4,'5',6,7,8,9,'10']

Benchmark.ips do |x|
 x.report("while") {
    hash   = {}
    index  = 0
    length = ARRAY.length

    while index < length
      hash[index] = ARRAY[index]
      index += 1
    end

    hash
  }

  x.report("each_with_index") {
    hash   = {}

    ARRAY.each_with_index do |item, index|
      hash[index] = item
    end

    hash
  }
end

Ruby 2.7.2, mbp 16" 2019

Warming up --------------------------------------
                 for    66.319k i/100ms
                 map    74.178k i/100ms
Calculating -------------------------------------
                 for    679.577k (± 2.4%) i/s -      3.449M in   5.077525s
                 map    750.524k (± 2.5%) i/s -      3.783M in   5.043778s

Warming up --------------------------------------
               while    64.774k i/100ms
     each_with_index    52.388k i/100ms
Calculating -------------------------------------
               while    756.853k (±12.2%) i/s -      3.757M in   5.041195s
     each_with_index    532.295k (± 8.2%) i/s -      2.672M in   5.055235s