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From: Andreas Ericsson <ae@op5.se>
To: Walter Bright <boost@digitalmars.com>
Cc: git@vger.kernel.org
Subject: Re: [RFC] Convert builin-mailinfo.c to use The Better String Library.
Date: Fri, 07 Sep 2007 11:41:53 +0200	[thread overview]
Message-ID: <46E11CE1.4030209@op5.se> (raw)
In-Reply-To: <fbr2iv$ugg$1@sea.gmane.org>

Walter Bright wrote:
> Wincent Colaiuta wrote:
>> Git is all about speed, and C is the best choice for speed, especially 
>> in context of Git's workload.
> 
> I can appreciate that. I originally got into writing compilers because 
> my game (Empire) ran too slowly and I thought the existing compilers 
> could be dramatically improved.
> 
> And technically, yes, you can write code in C that is >= the speed of 
> any other language (other than asm). But practically, this isn't 
> necessarily so, for the following reasons:
> 
> 1) You wind up having to implement the complex, dirty details of things 
> yourself. The consequences of this are:
> 
>    a) you pick a simpler algorithm (which is likely less efficient - I 
> run across bubble sorts all the time in code)
> 
>    b) once you implement, tune, and squeeze all the bugs out of those 
> complex, dirty details, you're reluctant to change it. You're reluctant 
> to try a different algorithm to see if it's faster. I've seen this 
> effect a lot in my own code. (I translated a large body of my own C++ 
> code that I'd spent months tuning to D, and quickly managed to get 
> significantly more speed out of it, because it was much simpler to try 
> out different algorithms/data structures.)
> 

I haven't seen this in the development of git, although to be fair, you
didn't mention the number of developers that were simultaneously working
on your project. If it was you alone, I can imagine you were reluctant to
change it just to see if something is faster.

Opensource projects with many contributors (git, linux) work differently,
since one or a few among the plethora of authors will almost always be
a true expert at the problem being solved.

The current pack-format and how it's read is one such example. It was
done once, by the combined efforts of Linus and Junio (this is all off
the top of my head and I cba to go looking up the details, so bear with
me if there are errors). Linus and Junio are both very good C-programmers,
but the handling of packfiles was not what you'd call their specialty.
Along came Nicolas Pitre, another excellent C programmer, who probably
has done some similar work before. He constructed a better algorithm,
eventually resulting in the ultimate performance win with a net gain
in both time and size (gj, Nicolas).

The point is that, given enough developers, *someone* is bound to
find an algorithm that works so well that it's no longer worth
investing time to even discuss if anything else would work better,
either because it moves the performance bottleneck to somewhere else
(where further speedups would no longer produce humanly measurable
improvements), or because the action seems instantanous to the user
(further improvements simply aren't worth it, because no valuable
resource will be saved from it).

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

  reply	other threads:[~2007-09-07  9:42 UTC|newest]

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-09-04 20:50 Lukas Sandström
2007-09-04 21:38 ` Alex Riesen
2007-09-04 23:01   ` Pierre Habouzit
2007-09-05 14:54 ` Kristian Høgsberg
2007-09-05 17:29   ` Matthieu Moy
2007-09-06  2:30     ` Miles Bader
2007-09-06  4:48     ` Dmitry Kakurin
2007-09-06  4:59       ` Shawn O. Pearce
2007-09-06  9:12         ` Andreas Ericsson
2007-09-06  9:35           ` Junio C Hamano
2007-09-06 10:21             ` Andreas Ericsson
2007-09-06  9:52           ` David Kastrup
2007-09-06  5:03       ` Miles Bader
2007-09-06 12:08         ` Johannes Schindelin
2007-09-06 17:50       ` Linus Torvalds
2007-09-07  0:21         ` Dmitry Kakurin
2007-09-07  0:38           ` Linus Torvalds
2007-09-07  1:08             ` Dmitry Kakurin
2007-09-07  1:27               ` Linus Torvalds
2007-09-07  3:09                 ` Dmitry Kakurin
2007-09-07  5:48                   ` David Symonds
2007-09-07  6:15                   ` Theodore Tso
2007-09-20 14:06                     ` Steven Burns
2007-09-20 14:56                       ` Andreas Ericsson
2007-09-07  6:31                   ` Andreas Ericsson
2007-09-07 22:17                     ` Dmitry Kakurin
2007-09-07 22:28                       ` David Kastrup
2007-09-08  0:37                         ` Dmitry Kakurin
2007-09-08  6:25                           ` David Kastrup
2007-09-09  0:29                       ` Andreas Ericsson
2007-09-07  6:52                   ` David Kastrup
2007-09-07 10:28                   ` Johannes Schindelin
2007-09-07 10:26                 ` Johannes Schindelin
2007-09-07  6:50               ` David Kastrup
2007-09-07  1:12             ` Linus Torvalds
2007-09-07  1:40               ` alan
2007-09-07  5:09               ` Walter Bright
2007-09-07  7:40                 ` David Kastrup
2007-09-07  8:15                   ` Walter Bright
2007-09-07  8:26                     ` David Kastrup
2007-09-07  9:14                       ` Walter Bright
2007-09-07  9:31                         ` David Kastrup
2007-09-07 20:22                           ` Walter Bright
2007-09-07 20:27                             ` David Kastrup
2007-09-07 23:16                               ` Walter Bright
2007-09-08 23:50                             ` Andreas Ericsson
2007-09-09  0:37                               ` Pierre Habouzit
2007-09-09  1:36                                 ` Andreas Ericsson
2007-09-07 11:36                   ` Wincent Colaiuta
2007-09-07  9:41                 ` Pierre Habouzit
2007-09-07 19:03                   ` Walter Bright
2007-09-07 19:31                     ` David Kastrup
2007-09-07 20:49                       ` Walter Bright
2007-09-07 19:41                     ` Pierre Habouzit
2007-09-07 19:51                       ` David Kastrup
2007-09-07 19:59                         ` Pierre Habouzit
2007-09-07 20:40                       ` Walter Bright
2007-09-07 20:56                         ` Pierre Habouzit
2007-09-07 22:54                           ` Walter Bright
2007-09-08  0:56               ` John 'Z-Bo' Zabroski
2007-09-08  6:36                 ` David Kastrup
2007-09-19 19:56               ` Steven Burns
2007-09-07  3:06           ` Wincent Colaiuta
2007-09-07  4:06             ` Paul Wankadia
2007-09-07  4:30               ` Nicolas Pitre
2007-09-07  9:19               ` Wincent Colaiuta
2007-09-07  6:25             ` Andreas Ericsson
2007-09-07 10:56               ` Johannes Schindelin
2007-09-07 11:54                 ` Andreas Ericsson
2007-09-07 12:33                   ` Wincent Colaiuta
2007-09-07 12:55                     ` Karl Hasselström
2007-09-07 13:58                     ` Andreas Ericsson
2007-09-07 14:13                       ` Wincent Colaiuta
2007-09-09  0:09                         ` Andreas Ericsson
2007-09-07 16:09                 ` David Kastrup
2007-09-07 11:30               ` Wincent Colaiuta
2007-09-07  8:36             ` Walter Bright
2007-09-07  9:41               ` Andreas Ericsson [this message]
2007-09-07 19:23                 ` Walter Bright
2007-09-07 19:40                   ` David Kastrup
2007-09-09  0:25                   ` Andreas Ericsson
2009-09-17 16:23                   ` Bernd Jendrissek
2007-09-07 11:52               ` Wincent Colaiuta
2007-09-07 19:25                 ` Walter Bright
2007-09-22 16:52               ` Steven Burns
2007-09-07  6:47           ` David Kastrup
2007-09-07  7:41             ` Andy Parkins
2007-09-07  8:08               ` David Kastrup
2007-09-07 10:21           ` Johannes Schindelin
2007-09-08  0:32             ` Dmitry Kakurin
2007-09-08  6:24               ` David Kastrup
2007-09-08 23:25               ` Alex Riesen
2007-09-24 13:41         ` figo
2007-09-24 13:57           ` David Kastrup
2007-09-25 19:19             ` Steven Burns
2007-09-25 19:55               ` David Kastrup
2012-05-22 18:30         ` Syed M Raihan
2010-06-10 19:12       ` Ian Molton
2010-06-11 12:23         ` Jakub Narebski
2010-06-11 13:33           ` Dario Rodriguez
2007-09-05 15:27 ` Kristian Høgsberg
2007-09-07 10:47 ` Lukas Sandström

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