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Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others


Hello!

> > 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 ;-)
>
> Also for math functions you can simply substitute the Intel compilers one
> (GCC uses the Microsoft ones) by linking against libimf.  You can also make
> 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.

However, even with -mveclibabi=svml, we still don't vectorize the call
to sincos ...

>From [1], it looks that the transcendental performance mostly depends
on math library code. I wonder if libimf handles calls with AVX
arguments to vectorized functions, so we can extend libimf support
code in gcc.

[1] http://willus.com/ccomp_benchmark2.shtml?p19

Uros.


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