From: Jordan Callicoat <monkeesage@...>
Date: 2006-08-29T17:21:24+09:00
Subject: Re: For performance, write it in C

=?iso-8859-1?Q?J=FCrgen?= Strobel wrote:
> On Sat, Aug 26, 2006 at 11:23:02PM +0900, Jordan Callicoat wrote:
>> J端rgen Strobel wrote:
> 
>> Yes! That's exactly what I was trying to do! I was trying to show that 
>> writing to stdout (assuming a comparable context, like an xterm) is the 
>> bottle-neck of the ruby version here. Writing to a file was about 90 
>> times faster. Like I said, I wasn't denying that C is faster; my point 
>> was this: the C version may only take 5 seconds to write to a *file*, 
>> but ruby only takes 17 seconds; and for me, as I'm sure for others, 12 
>> seconds is not worth the effort of writing it in C. So the 12 minutes to 
>> 5 seconds comparison was flawed -- 17 seconds to 5 seconds is more 
>> accurate.
> 
> Usually you don't benchmark with external arbitrary bottlenecks
> enabled. The point is, *your* xterm may be of very different speed
> than mine. Generic terminal emulators are not a comparable context at
> all, not without benchmarking them themselves, which is not the point
> of this exercise.
> 
> I should have emphasized *your terminal emulator*. We are comparing
> ruby vs. C, so it makes sense to assume a fast and uniform output
> mechanism which doesn't get in our way. It is standard practice to
> write to stdout, but redirect it to /dev/null or files if writeing
> larger quantities in benchmarks.
> 
> To get real numbers, your C version took 0.010s CPU time, and your
> ruby one took 0.202s. A difference of roughly 2000% may well be
> important to several applications. Sometimes it may be completely
> irrelevant, for instance if CPU time is dwarfed by I/O.
> 
> -J端rgen

I understand your point, but I think we may be talking past each other 
here. My purpose was to show that the ruby (and assumedly perl) 
bottle-neck was due other factors than the interpreter. Granted, ruby is 
slower than C -- even a lot slower (2000%!) -- but the end result of 
writing to a *file* is 17 seconds in ruby. That is light years removed 
from 26 (or even 12) minutes (i.e., writing to stdout with no 
redirection). So while 12 minutes versus 5 seconds may make you want to 
write it in C; 17 seconds versus 5 seconds may make you think twice 
about it. My question is, when is C a *necessary* evil, rather than just 
an evil. ;)

Regards,
Jordan

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