From: Charlie Somerville <charlie@...>
Date: 2013-07-31T14:24:54+09:00
Subject: [ruby-core:56277] Re: [ruby-trunk - Feature #8707][Feedback] Hash#reverse_each

Matz: This is quite a significant performance improvement and therefore I think it is worthwhile.

On 30/07/2013, at 20:48, "matz (Yukihiro Matsumoto)" <matz@ruby-lang.org> wrote:

> 
> Issue #8707 has been updated by matz (Yukihiro Matsumoto).
> 
> Status changed from Open to Feedback
> 
> Do we really need it?  What is use-cases?
> 
> Matz.
> 
> ----------------------------------------
> Feature #8707: Hash#reverse_each
> https://bugs.ruby-lang.org/issues/8707#change-40769
> 
> Author: Glass_saga (Masaki Matsushita)
> Status: Feedback
> Priority: Normal
> Assignee: 
> Category: core
> Target version: current: 2.1.0
> 
> 
> Currently, {}.reverse_each calls Enumerable#reverse_each.
> It will make array and its size can be large.
> I made Hash#reverse_each to avoid array creation and performance improvement.
> 
> benchmark:
> 
> require "benchmark"
> 
> Size = 10000
> HASH = Hash[*Array.new(Size) {|i| [i, true] }.flatten]
> 
> Benchmark.bmbm do |x|
>  x.report("Hash#reverse_each") do
>    300.times do
>      HASH.reverse_each {|a, b|}
>    end
>  end
> end
> 
> result:
> 
> trunk(r42256):
> Rehearsal -----------------------------------------------------
> Hash#reverse_each   1.210000   0.000000   1.210000 (  1.207964)
> -------------------------------------------- total: 1.210000sec
> 
>                        user     system      total        real
> Hash#reverse_each   0.950000   0.000000   0.950000 (  0.951069)
> 
> proposal: 
> Rehearsal -----------------------------------------------------
> Hash#reverse_each   0.600000   0.000000   0.600000 (  0.600242)
> -------------------------------------------- total: 0.600000sec
> 
>                        user     system      total        real
> Hash#reverse_each   0.450000   0.000000   0.450000 (  0.459006)
> 
> 
> -- 
> http://bugs.ruby-lang.org/
>