排序哈希的最快方法是什么？

Question

人们经常会问什么是对哈希进行排序的最佳方法,但是他们并没有问到所需的后续问题是什么是最快的方法,这确实是最好的方法.

无论使用何种Ruby版本,在Ruby中对Hash进行排序的最快方法是什么？

我正在寻找能够涵盖极端情况的其他答案,或者发现更通用和/或最快的方法的问题.

Answer 1

排序哈希的最快方法是什么？

require 'fruity'

HASH = Hash[('a'..'z').to_a.shuffle.map{ |k| [k, 1] }]

def sort_hash1(h)
  h.sort.to_h
end

def sort_hash2(h)
  Hash[h.sort]
end

def sort_hash3(h)
  Hash[h.sort_by{ |k, v| k }]
end

def sort_keys(h)
  keys = h.keys.sort
  Hash[keys.zip(h.values_at(*keys))]
end

puts "Running on Ruby v#{ RUBY_VERSION }"
puts

compare do
  do_sort_hash1 { sort_hash1(HASH) } if [].respond_to?(:to_h)
  do_sort_hash2 { sort_hash2(HASH) }
  do_sort_hash3 { sort_hash3(HASH) }
  do_sort_keys { sort_keys(HASH) }
end

在Mac OS便携式计算机上运行上述代码会产生以下输出:

# >> Running on Ruby v2.2.2
# >> 
# >> Running each test 256 times. Test will take about 1 second.
# >> do_sort_keys is faster than do_sort_hash3 by 39.99999999999999% ± 10.0%
# >> do_sort_hash3 is faster than do_sort_hash1 by 1.9x ± 0.1
# >> do_sort_hash1 is similar to do_sort_hash2

和:

# >> Running on Ruby v1.9.3
# >> 
# >> Running each test 256 times. Test will take about 1 second.
# >> do_sort_keys is faster than do_sort_hash3 by 19.999999999999996% ± 10.0%
# >> do_sort_hash3 is faster than do_sort_hash2 by 4x ± 0.1

加倍哈希大小:

HASH = Hash[[*('a'..'z'), *('A'..'Z')].shuffle.map{ |k| [k, 1] }]

结果是:

# >> Running on Ruby v2.2.2
# >> 
# >> Running each test 128 times. Test will take about 1 second.
# >> do_sort_keys is faster than do_sort_hash3 by 50.0% ± 10.0%
# >> do_sort_hash3 is faster than do_sort_hash1 by 2.2x ± 0.1
# >> do_sort_hash1 is similar to do_sort_hash2

和:

# >> Running on Ruby v1.9.3
# >> 
# >> Running each test 128 times. Test will take about 1 second.
# >> do_sort_keys is faster than do_sort_hash3 by 30.000000000000004% ± 10.0%
# >> do_sort_hash3 is faster than do_sort_hash2 by 4x ± 0.1

值将根据硬件而变化,但相对结果不应更改.

为简单起见,选择Fruity而不是使用内置的Benchmark类.

这是由" 按键排序哈希,在Ruby中返回哈希 "提示的.