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Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
On Thu, Jan 19, 2012 at 3:27 PM, willus.com <firstname.lastname@example.org> wrote:
> On 1/19/2012 2:59 AM, Richard Guenther wrote:
>> On Thu, Jan 19, 2012 at 7:37 AM, Marc Glisse<email@example.com> ?wrote:
>>> 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:
>>> For the math functions, this is normally more a libc feature, so you
>>> get very different results on different OS. Then again, by using
>>> -ffast-math, you allow the math functions to return any random value, so
>>> can think of ways to make it even faster ;-)
>> Also for math functions you can simply substitute the Intel compilers one
>> (GCC uses the Microsoft ones) by linking against libimf. ?You can also
>> use of their vectorized variants from GCC by specifying -mveclibabi=svml
>> and link against libimf (the GCC autovectorizer will then use the routines
>> from the Intel compiler math library). ?That makes a huge difference for
>> code using functions from math.h.
>>> Marc Glisse
> Thank you both for the tips. ?Are you certain that with the flags I used
> Intel doesn't completely in-line the math2.h functions at the compile stage?
Yes. Intel merely comes with its own (optimized) math library while GCC
has to rely on the operating system one.
> ?gcc? ?I take it to use libimf.a (legally) I would have to purchase the
> Intel compiler?
I would say you have to purchase the Intel compiler. Even then the
license to use
libimf.a may be restricted. So I wouldn't recomment distributing binaries
linked with libimf.a without consulting a lawyer.