From: Brian Candler <B.Candler@...>
Date: 2003-04-11T19:59:28+09:00
Subject: Re: Need IO Optimization help

On Fri, Apr 11, 2003 at 06:47:27PM +0900, Jim Freeze wrote:
> On Friday, 11 April 2003 at 17:47:39 +0900, Robert Klemme wrote:
> > Even if there are no improvements possible you should judge the effort of
> > improving speed of ruby vs. perl or others agains the effort to maintain a
> > changed ruby and the efforts saved by rubys higher development speed.  For
> > some script it's surely more efficient to write it in one hour and have it
> > run in another than to tweak a high performance perl script in four hours
> > that then runs in 15 minutes.
>  
>  For new scripts what you say is true. But I can't accept the fact 
>  that there are no improvements possible. And Ruby has no advantage 
>  when the Perl scripts already exist and are not being changed.

But Ruby has some fundamental disadvantages compared to Perl for this sort
of program. For example,
       count += 1
requires a method dispatch, and
       gets
requires the creation of a new object each time round the loop (and the
corresponding cleaning up of old objects), whereas when perl assigns to $_
I think it's just overwriting a global string buffer.

Both these 'handicaps' spring from Ruby's design which makes the writing of
large programs far more elegant, and I suspect when you're not just chucking
strings and around but doing operations with complex objects, the
performance difference will become less significant.

I suppose you could tweak the language to make it like Perl - for example
when reading lines have a method to overwrite an existing string instead of
allocating a new one:

       while $_.gets!
         .. perhaps
       end

But who wants to write ugly code like that for a small performance gain? You
might as well just use Perl in the first place.

In Perl a scalar is a scalar (except when it's a reference!!) - in Ruby
everything's an object. It's a big win for writing concise code quicky, and
I'm happy to take the performance hit. If it's "too slow to be useful" at
speed X then it's probably too slow to be useful at speed 2X either. In that
case you need a fundamental rethink to make it run at speed 10X or 100X.

Or just buy a dual-CPU box :-)

Regards,

Brian.