于 2012/2/9 18:35, xunxun 写道:
于 2012/2/9 18:29, Andrew Haley 写道:
On 02/09/2012 10:20 AM, xunxun wrote:
I use the code main.c (test sin speed)
On Win7 64bit, gcc 4.6.2 32bit
gcc -O3 -ffast-math main.c -o main.exe
run main.exe will cost 6.853s.
When linking with intel libM no fastmath
gcc -O3 main.c -o main.exe libmmt.lib libircmt.lib
run main.exe will cost 4.367s.
Ah okay, I get it now, its sin, not exp. I suspect that it's the
argument reduction step that's slowing you down.
Andrew.
I think so. I don't know whether I may change main.c 's sin to exp
It will be also slow.
And I think it's related with -funsafe-math-optimizations
If I only use the option, gcc also don't generate the symbol
The fastmath other option
-fno-math-errno, -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans, and -fcx-limited-range
don't have the effect.
--
Best Regards,
xunxun
