为什么Array.reverse_each比Array.reverse.each快 [英] Why Array.reverse_each is faster than Array.reverse.each

问题描述

我几乎不使用 reverse_each 方法，而不是我呼吁 reverse.each ，当我需要向后遍历数组。所以，我只是做了一些基准，显然 reverse_each 比 reverse.each 显著更快。

• 这是因为使用时通过它迭代之前创建一个反向阵​​列相关联的时间元素 reverse.each ？

但在我的例子为1000万次迭代 TIME（反向）+ TIME（每个）（下） - TIME（reverse.each）〜1.2秒的数组尺寸4.而这个时间差或多或少的住宿稳定不论数组的大小。我测试了它高达100元。

• 此一秒之差的原因是什么？

---

 要求'标杆'数=千万
ARR =（1..4）.to_aBenchmark.bm（13）做| X |
    x.report（reverse.each）{{number.times {arr.reverse.each | X | X} } }
    x.report（reverse_each）{{number.times {arr.reverse_each | X | X} } }
    x.report（反向）{number.times {arr.reverse}}
    x.report（每）{{number.times {arr.each | X | X} } }
结束
 

解决方案

我肯定会说，它已与时间建立反向关联数组做的！你只尝试了非常小的数组（100元素的数组仍然是一个小阵）。如果你试图用更大的阵列（例如10K元素），我觉得你真的会发现其中的差别。

I hardly use reverse_each method, instead I call upon reverse.each when I need to traverse an array backwards. So I just did some benchmarking and apparently reverse_each is significantly faster than reverse.each.

• Is this because there is an element of time associated with creating a reverse array before iterating through it when using reverse.each?

However in my example (below) of 10 million iterations TIME(reverse) + TIME(each) - TIME(reverse.each) ~ 1.2 seconds for an array of size 4. And this time difference more or less stays stable irrespective of the size of array. I have tested it for upto 100 elements.

• What accounts for this one second difference?

---

require 'benchmark'

number = 10000000
arr = (1..4).to_a

Benchmark.bm(13) do |x|
    x.report("reverse.each") { number.times { arr.reverse.each {|x| x} } }
    x.report("reverse_each") { number.times { arr.reverse_each {|x| x} } }
    x.report("reverse")      { number.times { arr.reverse } }             
    x.report("each")         { number.times { arr.each {|x| x} } }        
end

解决方案

I would definitely say it has to do with the time associating with creating the reverse array! You've only tried really small arrays (an array with 100 elements is still a small array). If you try with bigger arrays (for instance 10k elements), I think you will really notice the difference.

这篇关于为什么Array.reverse_each比Array.reverse.each快的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！