From: pat eyler <pat.eyler@...>
Date: 2009-01-10T03:47:42+09:00
Subject: Re: Q: most efficient way to remove duplicate spaces in a string?

On Fri, Jan 9, 2009 at 11:29 AM, Chris Shea <cmshea@gmail.com> wrote:
> On Jan 9, 11:20 am, Mark  Watson <mark.wat...@gmail.com> wrote:
>> I don't usually worry too much about efficiency unless runtime
>> performance becomes an issue so I use a_string.split.join(' ') to
>> remove extra spaces because the code is short and readable.
>>
>> This is certainly inefficient. What is the fastest idiom for this
>> operation?
>>
>> Thanks,
>> Mark
>
> Haven't benchmarked it,


require 'benchmark'

n = 1_000_000

Benchmark.bm(10) do |x|
  x.report("gsub") { n.times do
      "This     is  a test   string.".gsub(/ +/, ' ')
    end
  }
  x.report("gsub!") { n.times do
      "This     is  a test   string.".gsub!(/ +/, ' ')
    end
  }
  x.report("split.join") { n.times do
      "This     is  a test   string.".split.join(' ')
    end
  }
end


                user     system      total        real
gsub        6.310000   0.080000   6.390000 (  7.135028)
gsub!       6.300000   0.070000   6.370000 (  7.064374)
split.join  3.940000   0.070000   4.010000 (  4.160529)


or, with bmbm

pate@pate:~/scratch$ ./stringcleanup.rb
Rehearsal ----------------------------------------------
gsub         6.290000   0.170000   6.460000 (  7.956565)
gsub!        6.370000   0.170000   6.540000 (  8.128309)
split.join   3.990000   0.080000   4.070000 (  4.832332)
------------------------------------ total: 17.070000sec

                 user     system      total        real
gsub         6.220000   0.130000   6.350000 (  7.613061)
gsub!        6.390000   0.080000   6.470000 (  8.284855)
split.join   3.970000   0.120000   4.090000 (  5.684406)


Please, benchmark first.  It's not that hard:

http://on-ruby.blogspot.com/2008/12/benchmarking-makes-it-better.html



>  but this sounds like a case for regular
> expressions.
>
>  a_string.gsub!(/ +/, ' ')
>
> HTH,
> Chris
>
>



-- 
thanks,
-pate
-------------------------
   Duty makes us do things, Love make us do things well.
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