From: ara.t.howard@...
Date: 2006-07-28T01:20:30+09:00
Subject: Re: String#chop slow?  REALLY slow?

On Fri, 28 Jul 2006, Mat Schaffer wrote:

> I just did a quick benchmark to prove something to myself.  But I'd like to 
> get a sanity check from the people on the list.
>
> Basically I want to drop what will be a trailing "\n" from input.  But it 
> appears that using String#[] and if statements is nearly 200 times more 
> efficient than chop.   Which just seems really weird, so here's the 
> benchmark.  Maybe I'm doing something wrong.
>
> Does this seem right?  Anyone care to comment?
>
> ---- index_vs_chop.rb
>
> require 'benchmark'
>
> n = 100_000
> bigstring = "I am a big string " * 5_000
>
> Benchmark.bmbm do |bench|
>  bench.report("Indexing") {
>    n.times do
>      bigstring[0..-1]
>    end
>  }
>
>  bench.report("Chop") {
>    n.times do
>      bigstring.chop
>    end
>  }
> end
>
> ---- end index_vs_shop.rb
>
> output:
>
> Rehearsal --------------------------------------------
> Indexing   0.100000   0.000000   0.100000 (  0.102362)
> Chop       7.190000  13.890000  21.080000 ( 22.477807)
> ---------------------------------- total: 21.180000sec
>
>               user     system      total        real
> Indexing   0.100000   0.000000   0.100000 (  0.108777)
> Chop       7.290000  14.050000  21.340000 ( 22.755782)

on my node:

harp:~ > ruby a.rb
Rehearsal --------------------------------------------
Indexing   0.150000   0.000000   0.150000 (  0.145923)
Chop       4.210000  16.200000  20.410000 ( 20.910127)
Chop2      4.210000   0.220000   4.430000 (  4.536517)
---------------------------------- total: 24.990000sec

                user     system      total        real
Indexing   0.140000   0.000000   0.140000 (  0.142257)
Chop       0.110000   0.000000   0.110000 (  0.104612)
Chop2      0.150000   0.000000   0.150000 (  0.152083)


harp:~ > cat a.rb
require 'benchmark'

n = 100_000
bigstring = "I am a big string " * 5_000

Benchmark.bmbm do |bench|
   bench.report("Indexing") {
     n.times do
       bigstring[0..-1]
     end
   }

   bench.report("Chop") {
     n.times do
       bigstring.chop
     end
   }

   bench.report("Chop2") {
     n.times do
       bigstring = bigstring[0..-2]
     end
   }
end




-a
-- 
we can never obtain peace in the outer world until we make peace with
ourselves.
- h.h. the 14th dali lama