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From: Walter Bright <boost@digitalmars.com>
To: git@vger.kernel.org
Subject: Re: [RFC] Convert builin-mailinfo.c to use The Better String Library.
Date: Fri, 07 Sep 2007 01:36:56 -0700	[thread overview]
Message-ID: <fbr2iv$ugg$1@sea.gmane.org> (raw)
In-Reply-To: <D7BEA87D-1DCF-4A48-AD5B-0A3FDC973C8A@wincent.com>

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.)

2) Garbage collection has an interesting and counterintuitive 
consequence. If you compare n malloc/free's with n gcnew/collections, 
the malloc/free will come out faster, and you conclude that gc is slow. 
But that misses one huge speed advantage of gc - you can do FAR fewer 
allocations! For example, I've done a lot of string manipulating 
programs in C. The basic problem is keeping track of who owns each 
string. This is done by, when in doubt, make a copy of the string.

But if you have gc, you don't worry about who owns the string. You just 
make another pointer to it. D takes this a step further with the concept 
of array slicing, where one creates windows on existing arrays, or 
windows on windows on windows, and no allocations are ever done. It's 
just pointer fiddling.

------
Walter Bright
http://www.digitalmars.com  C, C++, D programming language compilers
http://www.astoriaseminar.com  Extraordinary C++

  parent reply	other threads:[~2007-09-07  8:37 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 [this message]
2007-09-07  9:41               ` Andreas Ericsson
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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