Hash[] vs Array#to_h

hash_bench.rb

require 'benchmark/ips'

DEFAULT_CHARSET = ('a'..'z').to_a + (0..9).to_a

def random_symbol
  charset = ('a'..'z')
  random_string(charset).to_sym
end

def random_string(charset = DEFAULT_CHARSET)
  length = rand(10) + 3
  length.times.map { charset.to_a.sample }.join
end

NESTED_ARRAY = 1000.times.map { [random_symbol, random_string] }
FLAT_ARRAY = NESTED_ARRAY.flatten

Benchmark.ips do |x|
  x.report('Hash[] nested array', 'Hash[NESTED_ARRAY]')

  x.report('Hash[] flat array', 'Hash[*FLAT_ARRAY]')

  x.report('Array#to_h', 'NESTED_ARRAY.to_h')

  x.compare!
end

results

Calculating -------------------------------------
 Hash[] nested array   174.000  i/100ms
   Hash[] flat array   186.000  i/100ms
          Array#to_h   204.000  i/100ms
-------------------------------------------------
 Hash[] nested array      2.058k (±24.2%) i/s -      9.222k
   Hash[] flat array      2.140k (±23.7%) i/s -      9.672k
          Array#to_h      2.008k (±21.5%) i/s -      9.588k

Comparison:
   Hash[] flat array:     2139.9 i/s
 Hash[] nested array:     2057.8 i/s - 1.04x slower
          Array#to_h:     2008.2 i/s - 1.07x slower

specs

hash_bench: ruby -v
ruby 2.2.1p85 (2015-02-26 revision 49769) [x86_64-darwin14]

hash_bench: system_profiler SPHardwareDataType
Hardware:

    Hardware Overview:

      Model Name: MacBook Pro
      Model Identifier: MacBookPro11,1
      Processor Name: Intel Core i5
      Processor Speed: 2,6 GHz
      Number of Processors: 1
      Total Number of Cores: 2
      L2 Cache (per Core): 256 KB
      L3 Cache: 3 MB
      Memory: 8 GB