[gameprogrammer] Re: Fixed point vs floating point in modern computers

  • From: Jonathan Dearborn <grimfang4@xxxxxxxxx>
  • To: gameprogrammer@xxxxxxxxxxxxx
  • Date: Sun, 19 Feb 2012 17:00:02 -0500

Fixed point does still have its place.  Sprig uses it and squeezes out a
good bit of speed for software image transformations.  I would suggest that
you write a simple benchmark (like a matrix multiplication loop) that we
could run on our machines to gather data for you.  I'm not up on my SSE
knowledge, but there are SIMD instructions out there for integers.

Jonny D

On Sun, Feb 19, 2012 at 4:34 PM, Alan Wolfe <alan.wolfe@xxxxxxxxx> wrote:

> Hey Guys,
> I was curious, does anyone know any metrics about how fast fixed point
> math operations are compared to floating point math operations on modern
> desktops/laptops?
> There's an annoying issue i've been trying to solve in my google native
> client app where some systems have different levels of floating point math
> precision (internal float registers being 80 bits sometimes, and sometimes
> not, different machines spilling calculations onto the stack for
> temporaries etc) and while i've been talking to the google nacl devs on the
> mailing list, i'm wondering if going to fixed point may be a decent
> solution.
> The worry of mine though is that going to fixed point i'd lose out on any
> SSE operations as well as perhaps thinking that even well written fixed
> point math may not be as fast as hardware calculated floating point math.
> But, of course what would be great is that whatever i see on my machine is
> what other people would see on theirs, which is really attractive.
> This is for a raytracer so is very heavy on floating point computation,
> and apparently pretty sensitive to floating point precision issues.
> What do you guys think, anyone have any insight or input?

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