From: Mike Stok <mike@...>
Date: 2006-03-12T01:51:43+09:00
Subject: Re: Help me understand why the Ruby block is slower than wit


On 11-Mar-06, at 11:09 AM, Alan Burch wrote:

> James Gray wrote:
>> On Mar 10, 2006, at 5:28 PM, William James wrote:
>>
>>> File.open("wordlist") { |f|
>>>   while w = f.gets
>>>      puts w  if w.size==11 && w.split(//).uniq.size == 11
>>>   end
>>> }
>>
>> That's what the foreach() iterator is for:
>>
>> File.foreach("wordlist") do |word|
>>    puts word if word.chomp.split("").uniq.size == 10
>> end
>>
>> James Edward Gray II
>
> James:
> This code doesn't work on my Mac.  I do have a version that uses the
> file block and each/foreach above, but I'm suspecting that when the
> string becomes an array after the split something's breaking down as I
> get words of all sizes out???
>

Doesn't James Gray's code print out words which contain exactly 11  
different letters e.g.

abbreviations - 13 characters + \n, but because it wasn't checked for  
size before splitting this boils down to 10 different characters.

irb(main):001:0> s = 'abbreviations'
=> "abbreviations"
irb(main):002:0> s.split('').uniq
=> ["a", "b", "r", "e", "v", "i", "t", "o", "n", "s"]
irb(main):003:0> s.split('').uniq.size
=> 10


Interesting.  I crudely benchmarked this (using time on my mac):

#!/usr/bin/env ruby

File.foreach("K6wordlist.txt") do |word|
    # puts word if word.size==11 && word.split(//).uniq.size == 11
      puts word if word.length == 11 and word.chomp.split 
(//).uniq.size == 10
    # puts word if word.length == 11 and not word =~ /(.).*\1/
end

and then ran each of the three sending output to /dev/null (after  
checking that they all worked the same on my test file.  In order:

real    0m0.347s
user    0m0.294s
sys     0m0.017s

real    0m0.334s
user    0m0.288s
sys     0m0.018s

real    0m0.177s
user    0m0.137s
sys     0m0.015s

There may be interesting behaviour if the last line in the file  
doesn't have a trailing \n, I would probably go for something more like

File.foreach("K6wordlist.txt") do |word|
    word.chomp!
    puts word if word.length == 10 and not word =~ /(.).*\1/
end

(timing intentionally omitted :-)

Mike

-- 

Mike Stok <mike@stok.ca>
http://www.stok.ca/~mike/

The "`Stok' disclaimers" apply.