Re: ANN: LuaJIT 1.1.0 / Re: Lua x DirectX

["Framework Studios: Hugo" <hugo@...>]

Well, one number I found on the decrease of Direct3D's speed with and 
without the FPU preserve flag:

http://discuss.microsoft.com/SCRIPTS/WA-MSD.EXE?A2=ind0504b&L=directxdev&D=1&P=3121

with: 560 fps
without: 580 fps

However I think it is a bit beside the point to 'prove' this with numbers 
since DirectX more or less already chose single precision for us (for a good 
reason, I trust). Also it seems logical for a 3D API to be faster when using 
float-s in stead of double-s because twice the data can be pushed to the GPU 
with the same bandwidth / stored in VRAM. Isn't this the same for OpenGL?

Looking at the performance of double vs float on modern CPU-s should be 
interesting though. Are double-s faster, slower or the same compared to 
float-s on 32-bit and 64-bit CPU architecture? What about the CPU-s people 
are actually using on average at the moment? (to sell games we need to look 
at what is average on the market, not only to what is top-notch :)

       Cheers,
               Hugo

----- Original Message ----- 
From: "Andras Balogh" <andras.balogh@gmx.net>
To: "Lua list" <lua@bazar2.conectiva.com.br>
Sent: Thursday, March 16, 2006 2:51 PM
Subject: Re: ANN: LuaJIT 1.1.0 / Re: Lua x DirectX


> I still don't buy this. Give me numbers! Should be easy, right? Set
> the flag and read FPS counter! I'd test it myself, but I'm using
> OpenGL, and thus never had to change the FPU control word..
>
>
> Andras
>
> Thursday, March 16, 2006, 1:35:08 AM, you wrote:
>
> > A google search can also produce pages about the loss of speed when using
> > the 'preserve FPU' flag, like
> > http://discuss.microsoft.com/SCRIPTS/WA-MSD.EXE?A2=ind0504b&L=directxdev&D=1&P=4524
> > (quote: "For games, you typically don't want the performance hit of 
> > having
> > the FP unit working in double-precision.").