Re: "float complex" arithmetic performance much slower than expected

[Michele Martone <michele dot martone at ipp dot mpg dot de>]

On 20130306@12:08, Tim Prince wrote:
> > >  . CFLAGS for gcc:
> >"-O3 -pipe -march=native -mtune=native -mavx -std=c99 -fno-unroll-loops"
> >  . CFLAGS for icc: "-O3 -xAVX -restrict -unroll=0"
> > ...
> >Do you find this consistent with your experience in "complex" and gcc,
> >or it may be the case I am ignoring some basic rule in using gcc ?
> >
> In the absence of -fcx-limited-range, gcc may protect divide and
> sqrt by using library functions, where icc would simply widen to
> double.  You would see any such library function usage if you
> profiled by gprof, at least when the library is static linked. Also,
> the library functions used by gcc aren't vectorized, while icc would
> go further toward promoting vectorization by in-lining code or
> calling vector math functions.
In man gcc I see that -fcx-limited-range affects both multiplication and
division, while -fcx-fortran-rules only division. 

The functions in my code only contain integer/floating point array accesses
and add / multiply operations.
So only multiplications may be accelerated by this or -ffast-math.

And as you suggest, man icc says -no-complex-limited-range is the
default, so  icc -O3  would need at least -complex-limited-range to be
fairly compared to gcc -ffast-math .

> Vectorization reports for both compilers would shed light on this question.
Ok: Could you please suggest the options for getting "enough, but not too
many" report info ?