gfortran speed benchmarks

[Tim Prince]

Ron Young wrote:
> The Intel compiler is almost always used with -xW -ipa flags. If you
> use -march=pentium4 , you should use -xW. The option -ipa will give you
> inlining. Polyhedron posted the flags they used.
> The option -ffast-math should be used with gfortran.
> 
> Ron Young
> 
> 
gfortran -ftree-vectorize -march=pentium4 -mfpmath=sse -ffast-math -O3 
is a closer equivalent to ifort -xW -ip, except for the excessive use of 
x87 intrinsics in common versions of mathinline.h. Some of the problems 
with -ffast-math stem from shortcuts and errors in the mathinline.h . 
ifort 9.0 has some options which allow it to come closer to the behavior 
of gfortran without -ffast-math, but you won't see them in the 
Polyhedron choices.