Option Checking in Ruby: Hash vs Bitwise Operations This is a simple script that compares how fast it is to build option dictionaries and checking them versus using integers and bitwise flagging

gistfile1.rb

require 'benchmark'

class HashedFlags
  def initialize(opts = {})
		@silly_prepend = opts.fetch(:silly_prepend, false)
		@uppercase = opts.fetch(:uppercase, false)
	end
end

SILLY_PREPEND 	= 0b00000001
UPPERCASE 		= 0b00000010

class BitFlags
	def initialize(flags)
		@silly_prepend = (flags & SILLY_PREPEND) > 0
		@uppercase = (flags & UPPERCASE) > 0
	end
end

iterations = 5000000

Benchmark.bm(50) do |bm|
	bm.report('using hashes as option flags') do
		iterations.times do |i|
			hash_set = case i%4
			when 0 then {}
			when 1 then {:silly_prepend => true}
			when 2 then {:uppercase => true}
			when 3 then {:silly_prepend => true, :uppercase => true}
			end

			HashedFlags.new(hash_set)
		end
	end

	bm.report('using bitwise flags as option flags') do
		iterations.times do |i|
			flags = case i%4
			when 0 then 0
			when 1 then SILLY_PREPEND
			when 2 then UPPERCASE
			when 3 then SILLY_PREPEND | UPPERCASE
			end

			BitFlags.new(flags)
		end
	end
end

# My Results:
#                                                          user     system      total        real
# using hashes as option flags                        12.730000   0.030000  12.760000 ( 12.768373)
# using bitwise flags as option flags                  7.080000   0.010000   7.090000 (  7.092274)
#
#
# Just for fun, I ran a similar test under Xcode with ObjC Objects initalized with dictionaries, 
# ObjC Objects initialized with flags, and C structs initialized with flags:
# Time elapsed using ObjC objects and flags: 1.151373
# Time elapsed using ObjC objects and Dictionaries: 5.105790
# Time elapsed using c structs with flags: 0.061645


# UPDATE: Reran the C code again with optimized build settings:
# Time elapsed using ObjC objects and flags: 0.732126
# Time elapsed using ObjC objects and Dictionaries: 4.424255
# Time elapsed using c structs with flags: 0.000001 (Not sure if the compiler knew nothing was being used and just removed the loop or if it really went this fast)