def rran()
  s = 0
  (0..10000000).each do |i|
    s += i
  end
end

def tfor()
  n=0
  s=0
  while (n+=1) < 10000000
    s+=n
  end

end
[148] pry(main)> Benchmark.measure { tfor()}
=> #<Benchmark::Tms:0x000000029cf458
 @cstime=0.0,
 @cutime=0.0,
 @label="",
 @real=0.22141856199596077,
 @stime=0.0,
 @total=0.21999999999999997,
 @utime=0.21999999999999997>
[149] pry(main)> Benchmark.measure { rran()}                                                              
=> #<Benchmark::Tms:0x00000002969388
 @cstime=0.0,
 @cutime=0.0,
 @label="",
 @real=0.3831686199409887,
 @stime=0.0,
 @total=0.3700000000000001,
 @utime=0.3700000000000001>

如图 for 版本的循环比 range 版本的快很多。按道理应该是一样快才对啊。请大牛解释一下