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Bug #13917

closed

Comparable#clamp is slower than using Array#min,max.

Added by kei-s (Kei Shiratsuchi) over 6 years ago. Updated over 4 years ago.

Status:
Rejected
Target version:
-
[ruby-dev:50254]

Description

Comparable#clamp is slower than using Array#min,max.
(I noticed it by @onk's tweet. https://twitter.com/onk/status/907856892604461056)

Performance

              user     system      total        real
minmax:   0.740000   0.000000   0.740000 (  0.732744)
clamp:    2.060000   0.010000   2.070000 (  2.072794)

Test Code

require 'benchmark'

Benchmark.bmbm do |x|
  v = Random.rand(-10..110)

  x.report "minmax:" do
    10000000.times { [99, [0, v].max].min }
  end

  x.report "clamp: " do
    10000000.times { v.clamp(0, 99) }
  end
end

Patch

I made patch for it. But I'm not sure this is good way.
https://gist.github.com/kei-s/b303aca105df5c26be9c98f833db80f7#file-compar-diff

After

              user     system      total        real
minmax:   0.820000   0.000000   0.820000 (  0.822517)
clamp:    1.090000   0.000000   1.090000 (  1.087491)

Other benchmark for this patch is here.
https://gist.github.com/kei-s/0c34cbe4e21a499601e8247077629082

Questions

  1. Should clamp version be faster than Array#min/max version?
    Array#min/max version would have overhead of array creation.

  2. Is OPTIMIZED_CMP in cmpint best way?
    Some method doesn't pass cmpint (e.g. Integer#>). But OPTMIZED_CMP checks Integer.

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