From: Thomas E Enebo <enebo@...>
Date: 2006-08-02T04:32:06+09:00
Subject: Re: For performance, write it in C - Part 3, Source code now available

On Wed, 02 Aug 2006, Charles O Nutter defenestrated me:
> 
> First, some notes on benchmarking:
> 
> - NEVER include IO when benchmarking a numeric algorithm; IO speeds vary
> greatly from system to system and can vary from run to run depending on what
> else is happening

  IO can be noisy. I say avoid it for any benchmarking since it can
greatly influence timings.  Usually the IO is not what you want to 
measure so why add this variable into things?
  
> - If you're building up a large chunk of strings, write to an internal
> buffer and then write out at the end; don't write for every little tiny
> operation. At the very least, use a buffer per-line, rather than a separate
> write for every element on that line.

  I just informally thought I would measure a few things involving IO.
I only changed the printing and nothing else:

Unaltered test: ~3.8s
Use of StringBuffer to print out a single row: ~2.1s
Use of StringBuffer for entire run: ~1.5s
Preallocated StringBuffer for entire run: ~1.4s

  As you can see IO can have a large affect on clock time.  I demonstrated
that in Java's case the IO in the benchmark accounted for over 2/3 of the
wall clock time (which is interesting because a decent chunk that is
left over is JVM startup overhead).

Some stack allocated space will likely improve the C run as well (and in 
this case you can output it in a single write system call). 

-Tom

-- 
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| Thomas E Enebo, Protagonist  | "Luck favors the prepared    |
|                              |  mind." -Louis Pasteur       |