From: "trans (Thomas Sawyer)" <redmine@...>
Date: 2013-08-27T08:19:46+09:00
Subject: [ruby-core:56816] [ruby-trunk - Feature #8820] Speed up Array#index


Issue #8820 has been updated by trans (Thomas Sawyer).


Yes, sorry. I meant to use a random index with each iteration, not `i`. But per the suggestion, I think `i % 100` would be better.

I changed and reran the benchmarks. But even so the comparison still comes out about the same ratio:

Ruby: 35.66597
Go: 1.39305



----------------------------------------
Feature #8820: Speed up Array#index
https://bugs.ruby-lang.org/issues/8820#change-41357

Author: trans (Thomas Sawyer)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: next minor


I did a quick comparison:

In Ruby

    def main
      n = 10000000  # ten million
      a = randPerm(100)

      t0 = Time.now

      n.times do |i|
        a.index(i)
      end

      puts "%.5f" % [Time.now - t0]
    end

    def randPerm(n)
      (0...n).sort_by{rand}
    end

    main()

In Go

    package main

    import (
      "fmt"
      "time"
      "math/rand"
    )

    func main() {
      n := 10000000  // ten million
      a := rand.Perm(100)

      t0 := time.Now()

      for i := 0; i < n; i++ {
        index(a, i)
      }

      fmt.Printf("%.5f\n", time.Now().Sub(t0).Seconds())
    }

    func index(slice []int, value int) int {
      for i, v := range slice {
        if (v == value) {
          return i
        }
      }
      return -1
    }

The result

  Ruby: 71.08961 secs
    Go: 2.61975 secs

That's pretty huge difference (and worse I was told my Go index function was "crazily inefficient" too, though personally I don't see how it can be any better). So, I thought I'd mention it. Maybe it would be possible to speed up.




-- 
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