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comp.lang.python

time.time() strangeness

Nitro

2/27/2008 9:51:00 AM

Ok, my final solution is to add the D3DCREATE_FPU_PRESERVE flag. It didn't
harm performance in a noticeable way at all. I was under the impression
SSE would be affected by this, too. Additionally I was under the
impression that float precision would suffice for time.time(). Obviously I
was blatantly wrong :-)
Thanks to Gabriel, Ross and Roel for commenting on this and sharing their
insights!

They should really make the fpu preserve flag the default. It just causes
very sneaky bugs.

-Matthias
2 Answers

Ross Ridge

2/27/2008 6:12:00 PM

0

Nitro <nitro@dr-code.org> wrote:
>They should really make the fpu preserve flag the default. It just causes
>very sneaky bugs.

They did in Direct3D 10, which doesn't change the flags. It's too late
to change the behaviour Direct3D 9 which was created a time where changing
FPU precision could have an effect on low end configurations.

Ross Ridge

--
l/ // Ross Ridge -- The Great HTMU
[oo][oo] rridge@csclub.uwaterloo.ca
-()-/()/ http://www.csclub.uwaterloo.c...
db //

Roel Schroeven

2/27/2008 10:43:00 PM

0

Nitro schreef:
> Ok, my final solution is to add the D3DCREATE_FPU_PRESERVE flag. It didn't
> harm performance in a noticeable way at all. I was under the impression
> SSE would be affected by this, too. Additionally I was under the
> impression that float precision would suffice for time.time(). Obviously I
> was blatantly wrong :-)

Float precision might even be enough but DirectX (without the flag)
switches to even lower precision than that; only 22 bits IIRC.

> They should really make the fpu preserve flag the default. It just causes
> very sneaky bugs.

Absolutely.


Cheers,
Roel