Benchmarks for different ways of remapping the values of a hash

hash_map_values.rb

require 'benchmark/ips'

MONDO_HASH = (1..50).each_with_object({}) { |num, hash|
  hash[num.to_s] = num
}

# Monkey-patching a map_values to test; this should probably be a refinement
class Hash
  def map_values
    merge({}) { |key, value| yield(value) }
  end
end

Benchmark.ips do |x|
  # Only run the GC before and after each benchmark
  x.config(:suite => Class.new {
    def warming(*); run_gc; end
    def running(*); run_gc; end
    def warmup_stats(*); end
    def add_report(*); end

    private

    def run_gc
      GC.enable
      GC.start
      GC.disable
    end
  }.new)

  x.report("each_with_object") {
    MONDO_HASH.each_with_object({}) { |key_value, hash|
      key, value = key_value
      hash[key] = value + 1
    }
  }

  x.report("merge") {
    MONDO_HASH.merge({}) { |key, value| value + 1 }
  }

  x.report("merge self") {
    MONDO_HASH.merge(MONDO_HASH) { |key, value| value + 1 }
  }

  x.report("Hash[map]") {
    Hash[MONDO_HASH.map { |key, value| [key, value + 1] }]
  }

  x.report("long form") {
    hash = {}
    MONDO_HASH.each { |key, value|
      hash[key] = value + 1
    }
    hash
  }

  x.report("map_values monkey patch") {
    MONDO_HASH.map_values { |value|
      value + 1
    }
  }

  x.compare!
end