ruby - 是 &method( :method_name) idiom bad for performance in Ruby?

Question

我最近遇到了 &method(:method_name) 语法。 (这使用 Object#method 方法 - RDoc link)例如，

[5, 7, 8, 1].each(&method(:puts))

相当于

[5, 7, 8, 1].each{|number| puts number}

在 Ruby 的各种实现中，与前者相比，后者是否存在性能损失？如果是，实现者是否正在努力提高其性能？

Answer 1

是的，这似乎对性能不利。

def time
  start = Time.now
  yield
  "%.6f" % (Time.now - start)
end

def do_nothing(arg)
end


RUBY_VERSION # => "1.9.2"

# small
ary = *1..10
time { ary.each(&method(:do_nothing)) }     # => "0.000019"
time { ary.each { |arg| do_nothing arg } }  # => "0.000003"


# large
ary = *1..10_000
time { ary.each(&method(:do_nothing)) }     # => "0.002787"
time { ary.each { |arg| do_nothing arg } }  # => "0.001810"


# huge
ary = *1..10_000_000
time { ary.each(&method(:do_nothing)) }     # => "37.901283"
time { ary.each { |arg| do_nothing arg } }  # => "1.754063"

看起来这在 JRuby 中得到了解决:

$ rvm use jruby
Using /Users/joshuajcheek/.rvm/gems/jruby-1.6.3

$ xmpfilter f.rb 
def time
  start = Time.now
  yield
  "%.6f" % (Time.now - start)
end

def do_nothing(arg)
end


RUBY_VERSION # => "1.8.7"

# small
ary = *1..10
time { ary.each(&method(:do_nothing)) }     # => "0.009000"
time { ary.each { |arg| do_nothing arg } }  # => "0.001000"


# large
ary = *1..10_000
time { ary.each(&method(:do_nothing)) }     # => "0.043000"
time { ary.each { |arg| do_nothing arg } }  # => "0.055000"


# huge
ary = *1..10_000_000
time { ary.each(&method(:do_nothing)) }     # => "0.427000"
time { ary.each { |arg| do_nothing arg } }  # => "0.634000"