"float complex" arithmetic performance much slower than expected

[Alexander Monakov]

On Wed, 6 Mar 2013, Michele Martone wrote:


>  . CFLAGS for gcc:
> "-O3 -pipe -march=native -mtune=native -mavx -std=c99 -fno-unroll-loops"
>  . CFLAGS for icc: "-O3 -xAVX -restrict -unroll=0"

This makes a comparison "unfair" since the two compilers use different
optimization restrictions for floating-point operations by default (GCC is
conservative, and thus more restricted in optimizations).  See the
documentation for -ffast-math GCC option, and floating-point flags in the ICC
help (e.g. options -fp-model and -mp).

Alexander