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On 1/18/2012 10:37 PM, Marc Glisse wrote:The default for the Intel compiler is more aggressive than gcc -ffast-math -fno-cx-limited-range, as long as you don't use one of the old buggy mathinline.h header files. For a fair comparison, you need detailed attention to comparable options. If you don't set gcc -ffast-math, you will want icc -fp-model-source.On Wed, 18 Jan 2012, willus.com wrote:
For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here:
http://willus.com/ccomp_benchmark2.shtml
http://en.wikipedia.org/wiki/Microsoft_Windows_SDK#64-bit_development
For the math functions, this is normally more a libc feature, so you might get very different results on different OS. Then again, by using -ffast-math, you allow the math functions to return any random value, so I can think of ways to make it even faster ;-)
I use -ffast-math all the time and have always gotten virtually identical results to when I turn it off. The speed difference is important for me.
-- Tim Prince
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