From: George Ogata <g_ogata@...>
Date: 2006-03-11T11:13:44+09:00
Subject: Re: Help me understand why the Ruby block is slower than wit

Alan Burch <orotone@gmail.com> writes:

>> File.open("wordlist") { |f|
>>   while w = f.gets
>>      puts w  if w.size==11 && w.split(//).uniq.size == 11
>>   end
>> }
>
> Ok, factor of 10 faster, and more Ruby like, much and many Thanks! 
> Others, any comments on the block slow down?

I don't see much of a slowdown.

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g@crash:~/tmp$ cat read-slow.rb
File.open("./words") { |f|
  while f.gets
    if $_.length == 11
      ar = $_.split(//)
      if ar.uniq! == nil
        print "#{ar.to_s}"
      end
    end
  end
}
g@crash:~/tmp$ /usr/bin/time ruby read-slow.rb > out-slow
2.56user 0.01system 0:02.64elapsed 97%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+550minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-slow.rb > out-slow
2.55user 0.01system 0:02.57elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+550minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-slow.rb > out-slow
2.54user 0.01system 0:02.56elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+550minor)pagefaults 0swaps
g@crash:~/tmp$ cat read-fast.rb
f = File.open("./words")
begin
  while f.gets
    if $_.length == 11
      ar = $_.split(//)
      if ar.uniq! == nil
        print "#{ar.to_s}"
      end
    end
  end
rescue EOFError
  f.close
end
g@crash:~/tmp$ /usr/bin/time ruby read-fast.rb > out-fast
2.51user 0.01system 0:02.54elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+544minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-fast.rb > out-fast
2.50user 0.01system 0:02.56elapsed 97%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+544minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-fast.rb > out-fast
2.51user 0.01system 0:02.53elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+544minor)pagefaults 0swaps

----------------------------------------------------------------------

There's a bit of a slowdown, but note that in your "fast" algo, the
stream is never closed, since IO#gets never throws EOFError.  Do `ri
IO#gets' for the method's documentation.  :-)

Another speedup:  replace:

  w.split(//).uniq.size == 11

with:

  w !~ /(.).*\1/

It's faster since there's less intermediate diddlage, but
theoretically it shouldn't scale as well.  You'd have to increase your
"11" quite a lot to notice it though I think.

More shell dump.

----------------------------------------------------------------------

g@crash:~/tmp$ cat read-one.rb
File.open("words") { |f|
  while w = f.gets
     puts w  if w.size==11 && w.split(//).uniq.size == 11
  end
}
g@crash:~/tmp$ /usr/bin/time ruby read-one.rb > out-one
2.54user 0.02system 0:02.57elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+548minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-one.rb > out-one
2.54user 0.01system 0:02.56elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+548minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-one.rb > out-one
2.55user 0.01system 0:02.58elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+548minor)pagefaults 0swaps
g@crash:~/tmp$ cat read-two.rb
File.open("words") { |f|
  while w = f.gets
    puts w  if w.size==11 && w !~ /(.).*\1/
  end
}
g@crash:~/tmp$ /usr/bin/time ruby read-two.rb > out-two
1.23user 0.01system 0:01.25elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+713minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-two.rb > out-two
1.27user 0.01system 0:01.29elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+713minor)pagefaults 0swaps
g@crash:~/tmp$ /usr/bin/time ruby read-two.rb > out-two
1.27user 0.02system 0:01.30elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+713minor)pagefaults 0swaps
g@crash:~/tmp$
g@crash:~/tmp$
g@crash:~/tmp$ diff out-one out-two
g@crash:~/tmp$

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