• Walter Bright (10/10) Jun 11 2007 The Astoria Seminar presents Extraordinary C++, a seminar for advanced
• Bill Baxter (10/23) Jun 11 2007 From the overview:
• Walter Bright (4/13) Jun 11 2007 It varies depending on the CPU. Also, some systems still use CPUs for
• Craig Black (3/3) Jun 24 2007 Fixed point math is also used in GPU programming occasionally. One examp...
• Bill Baxter (12/16) Jun 24 2007 We can program GPUs directly in C++ now?
• Craig Black (8/18) Jun 29 2007 Not without a shading language. But as you probably know, they are not ...

Walter Bright <newshound1 digitalmars.com> writes:

The Astoria Seminar presents Extraordinary C++, a seminar for advanced 
C++ programming. The seminar will be in Astoria, Oregon, from Sep. 23 to 
Sep. 26. The speakers are:

Walter Bright
Scott Meyers
Andrei Alexandrescu
Dave Abrahams
Eric Niebler

The seminar will be very small (only 55 people), so register early.

http://www.astoriaseminar.com/

Bill Baxter <dnewsgroup billbaxter.com> writes:

Walter Bright wrote:
 The Astoria Seminar presents Extraordinary C++, a seminar for advanced 
 C++ programming. The seminar will be in Astoria, Oregon, from Sep. 23 to 
 Sep. 26. The speakers are:
 
 Walter Bright
 Scott Meyers
 Andrei Alexandrescu
 Dave Abrahams
 Eric Niebler
 
 The seminar will be very small (only 55 people), so register early.
 
 http://www.astoriaseminar.com/

 From the overview:
"""This presentation will explore numerous techniques for speeding up 
the code. Areas covered include ... replacing floating point with fixed 
point"""
     --- http://www.astoriaseminar.com/astoria_seminar_sessions.html

Does using fixed point still help in anything but embedded systems these 
days?  I thought things had gotten to the point that most modern procs 
could do fp as fast or faster than integer math.

--bb

Walter Bright <newshound1 digitalmars.com> writes:

Bill Baxter wrote:
  From the overview:
 """This presentation will explore numerous techniques for speeding up 
 the code. Areas covered include ... replacing floating point with fixed 
 point"""
     --- http://www.astoriaseminar.com/astoria_seminar_sessions.html
 
 Does using fixed point still help in anything but embedded systems these 
 days?  I thought things had gotten to the point that most modern procs 
 could do fp as fast or faster than integer math.

It varies depending on the CPU. Also, some systems still use CPUs for 
embedded systems that have no FPU, and so using fixed point will head 
off the need for a (very slow) emulator.

"Craig Black" <cblack ara.com> writes:

Fixed point math is also used in GPU programming occasionally. One example
with the GeForce 6800+ is a zero cost fog computation.

-Craig

Bill Baxter <dnewsgroup billbaxter.com> writes:

Craig Black wrote:
 Fixed point math is also used in GPU programming occasionally. One example
 with the GeForce 6800+ is a zero cost fog computation.
 
 -Craig

We can program GPUs directly in C++ now?

Actually I do think fixed point is rather under-appreciated.  And not 
because of optimization.  For some things it just makes more sense to 
use fixed point.  For instance when storing coordinates, floating point 
gives you insane precision around zero, which degrades to downright 
lousy precision as you go far away from zero.  With a 64bit int you can 
have nice even precision over your whole world.  Works out that you can 
have something like sub-nanometer precision everywhere for a region as 
big as our solar system.  If you know how big your domain is, and zero 
is not special, then fixed point makes a lot of sense.

--bb

"Craig Black" <cblack ara.com> writes:

 We can program GPUs directly in C++ now?

Not without a shading language.  But as you probably know, they are not that 
hard to use, and they are becoming more friendly for general purpose 
computation.

 Actually I do think fixed point is rather under-appreciated.  And not 
 because of optimization.  For some things it just makes more sense to use 
 fixed point.  For instance when storing coordinates, floating point gives 
 you insane precision around zero, which degrades to downright lousy 
 precision as you go far away from zero.  With a 64bit int you can have 
 nice even precision over your whole world.  Works out that you can have 
 something like sub-nanometer precision everywhere for a region as big as 
 our solar system.  If you know how big your domain is, and zero is not 
 special, then fixed point makes a lot of sense.

Integer math is simpler and inherently faster.  However, for some reason on 
modern intel CPU's integer division is very slow.  Even slower than floating 
point division.  SSE instructions provide support for both floating-point 
and integral math, so using fixed point where appropriate is probably a good 
thing.  Division, as always, should be avoided as much as possible.