Re: GCC's -ffast-math behavior

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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.

--
Best Regards,
xunxun



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