From: "Christoffer Lernö" <lerno@...>
Date: 2007-09-29T02:27:34+09:00
Subject: Re: Ruby performance

On 28 Sep 2007, at 19:21, John Joyce wrote:

>
> On Sep 28, 2007, at 11:06 AM, khaines@enigo.com wrote:
>
>> On Sat, 29 Sep 2007, Vasyl Smirnov wrote:
>>
>>> Hi,
>>>
>>> I'm new to Ruby, and I've just tried to measure it's performance
>>> compared to Python, and got some interesting results.
>>>
>>> The Ruby test script is:
>>>
>>> #!/usr/bin/env ruby
>>>
>>> s = ""
>>> i = 0
>>> while line = gets
>>>  s += line
>>>  i += 1
>>>  puts(i) if i % 1000 == 0
>>> end
>>>
>>> and the Python one:
>>>
>>> #!/usr/bin/env python
>>>
>>> import sys
>>>
>>> s = ""
>>> i = 0
>>> for line in sys.stdin:
>>>  s += line
>>>  i += 1
>>>  if i % 1000 == 0: print i
>>>
>>>
>>> I fed a 1MB-large file as input to each of this script. The strange
>>> thing is that the Ruby version starts to output progress slower and
>>> slower as the s string grows. The Python version went smoothly.
>>
>> This is because "string" + "otherstring" allocates a new string,  
>> "stringotherstring".
>>
>> Use << instead, and it will concatenate "otherstring" to the  
>> orignal "string".
>>
>> s = ""
>> i = 0
>> while line = gets
>>  s << line
>>  i += 1
>>  puts(i) if i % 1000 == 0
>> end
>>
>> Performance should be a lot better with that version.
>>
>>
>> Kirk Haines
>>
>>
> That should be on a Ruby Optimization list somewhere!

Weird. The python version extremely slow compared to Kirk's ruby  
version. Does it suffer from the same allocation problems as the  
initial ruby version?


/C