ruby_performance.md

Useles to_s call

If you're converting some symbol with a method that assumes the string, than you have additional to_s -> method -> to_sym convertation

time ruby -e '100_000_000.times { "A".downcase }' # 6.70s user 0.06s system 93% cpu 7.254 total
time ruby -e '100_000_000.times { :A.downcase }'  # 8.39s user 0.04s system 99% cpu 8.497 total

Redundant attr_reader calls

class X
  attr_accessor :a, :b

  def initialize
    @a = 10
    @b = 20
  end

  def call(el)
    return true if el > a && el < b
    return false
  end
end

In this call method on every execution we call attr_reader to fetch a and b values

x = X.new

100_000_000.times do
  x.call(19)
end

If we replace a and b with a constants on this benchmark we'll save about 1.5s!

~ % time ruby ruby.rb
ruby ruby.rb  6.01s user 0.03s system 98% cpu 6.109 total
~ % time ruby ruby.rb
ruby ruby.rb  6.01s user 0.03s system 96% cpu 6.244 total
~ % time ruby ruby.rb
ruby ruby.rb  6.01s user 0.03s system 98% cpu 6.103 total

~ % time ruby ruby.rb
ruby ruby.rb  7.43s user 0.02s system 99% cpu 7.529 total
~ % time ruby ruby.rb
ruby ruby.rb  7.41s user 0.03s system 98% cpu 7.565 total
~ % time ruby ruby.rb
ruby ruby.rb  7.44s user 0.02s system 98% cpu 7.539 total