Floating point performance issue

Marcin Mirosław marcin@mejor.pl
Tue Dec 20 10:05:00 GMT 2011


W dniu 20.12.2011 10:52, Ico pisze:
> Hello,

Hi,

> I am able to reproduce this on multiple i686 boxes using various gcc versions
> (4.4, 4.6). Compiling on x86_64 does not show this behaviour.
> 
> Is anybody able to reproduce this issue, and how can this be explained ?

I can reproduce such situation too. I can only guess this happens
because on i686 default is mfpmath=387, on x86_64 default is
mfpmath=sse. If you compile your code using "-O3 -mfpmath=sse
-march=native <or something what else what have support for sse>" then
booth times will be almost equal.
Regards,



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