Till now we have not paid much attention to speed and possible optimization possibilities inherent in the various compilers. We have compiled and linked as

c++  -c  mycode.cpp
c++  -o  mycode.exe  mycode.o

For Fortran replace with for example gfortran or ifort. This is what we call a flat compiler option and should be used when we develop the code. It produces normally a very large and slow code when translated to machine instructions. We use this option for debugging and for establishing the correct program output because every operation is done precisely as the user specified it.

It is instructive to look up the compiler manual for further instructions by writing

man c++