http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53957
--- Comment #13 from Anthony Falzone <prop_design at yahoo dot com> --- My previous post needs a correction. Comparing gfortran O3 to Intel Fortran O3 I see a 60% speed improvement in favor of the Intel Fortran compiler. There is a 40% improvement over past releases of PROP_DESIGN, which used gfortran Ofast. There is not much difference between Intel Fortran O3 and Ofast, so I am using O3 to ensure accurate calculations.